Parser and Assembler implementations

Source/Core/Common/Assembler/AssemblerShared.cpp

@@ -0,0 +1,26 @@
+// Copyright 2023 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "Common/Assembler/AssemblerShared.h"
+
+#include <fmt/format.h>
+
+namespace Common::GekkoAssembler
+{
+std::string AssemblerError::FormatError() const
+{
+  const char* space_char = col == 0 ? "" : " ";
+
+  std::string_view line_str = error_line;
+  if (line_str.back() == '\n')
+  {
+    line_str = line_str.substr(0, line_str.length() - 1);
+  }
+
+  return fmt::format("Error on line {0} col {1}:\n"
+                     "  {2}\n"
+                     "  {3:{4}}{5:^^{6}}\n"
+                     "{7}",
+                     line + 1, col + 1, line_str, space_char, col, '^', len, message);
+}
+}  // namespace Common::GekkoAssembler

Source/Core/Common/Assembler/AssemblerShared.h

@@ -0,0 +1,545 @@
+// Copyright 2023 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <cstddef>
+#include <cstdint>
+#include <string>
+#include <string_view>
+#include <variant>
+
+namespace Common::GekkoAssembler
+{
+struct Interval
+{
+  size_t begin;
+  size_t len;
+  constexpr size_t End() const { return begin + len; }
+};
+
+struct AssemblerError
+{
+  std::string message;
+  std::string_view error_line;
+  size_t line;
+  size_t col;
+  size_t len;
+
+  std::string FormatError() const;
+};
+
+template <typename Tag, typename T>
+using Tagged = std::pair<Tag, T>;
+template <typename Tag, typename T>
+constexpr const Tag& TagOf(const Tagged<Tag, T>& val)
+{
+  return std::get<0>(val);
+}
+template <typename Tag, typename T>
+constexpr Tag& TagOf(Tagged<Tag, T>& val)
+{
+  return std::get<0>(val);
+}
+template <typename Tag, typename T>
+constexpr const T& ValueOf(const Tagged<Tag, T>& val)
+{
+  return std::get<1>(val);
+}
+template <typename Tag, typename T>
+constexpr T& ValueOf(Tagged<Tag, T>& val)
+{
+  return std::get<1>(val);
+}
+
+template <typename T>
+using FailureOr = std::variant<AssemblerError, T>;
+template <typename T>
+constexpr bool IsFailure(const FailureOr<T>& var)
+{
+  return std::holds_alternative<AssemblerError>(var);
+}
+template <typename T>
+constexpr AssemblerError& GetFailure(FailureOr<T>& var)
+{
+  return std::get<AssemblerError>(var);
+}
+template <typename T>
+constexpr const AssemblerError& GetFailure(const FailureOr<T>& var)
+{
+  return std::get<AssemblerError>(var);
+}
+template <typename T>
+constexpr const T& GetT(const FailureOr<T>& var)
+{
+  return std::get<T>(var);
+}
+template <typename T>
+constexpr T& GetT(FailureOr<T>& var)
+{
+  return std::get<T>(var);
+}
+
+enum class GekkoDirective
+{
+  Byte,
+  _2byte,
+  _4byte,
+  _8byte,
+  Float,
+  Double,
+  Locate,
+  PadAlign,
+  Align,
+  Zeros,
+  Skip,
+  DefVar,
+  Ascii,
+  Asciz
+};
+
+enum class GekkoMnemonic : size_t
+{
+  Add,
+  Addc,
+  Adde,
+  Addi,
+  Addic,
+  AddicDot,
+  Addis,
+  Addme,
+  Addze,
+  Divw,
+  Divwu,
+  Mulhw,
+  Mulhwu,
+  Mulli,
+  Mullw,
+  Neg,
+  Subf,
+  Subfc,
+  Subfe,
+  Subfic,
+  Subfme,
+  Subfze,
+  Cmp,
+  Cmpi,
+  Cmpl,
+  Cmpli,
+  And,
+  Andc,
+  AndiDot,
+  AndisDot,
+  Cntlzw,
+  Eqv,
+  Extsb,
+  Extsh,
+  Nand,
+  Nor,
+  Or,
+  Orc,
+  Ori,
+  Oris,
+  Xor,
+  Xori,
+  Xoris,
+  Rlwimi,
+  Rlwinm,
+  Rlwnm,
+  Slw,
+  Sraw,
+  Srawi,
+  Srw,
+  Fadd,
+  Fadds,
+  Fdiv,
+  Fdivs,
+  Fmul,
+  Fmuls,
+  Fres,
+  Frsqrte,
+  Fsub,
+  Fsubs,
+  Fsel,
+  Fmadd,
+  Fmadds,
+  Fmsub,
+  Fmsubs,
+  Fnmadd,
+  Fnmadds,
+  Fnmsub,
+  Fnmsubs,
+  Fctiw,
+  Fctiwz,
+  Frsp,
+  Fcmpo,
+  Fcmpu,
+  Mcrfs,
+  Mffs,
+  Mtfsb0,
+  Mtfsb1,
+  Mtfsf,
+  Mtfsfi,
+  Lbz,
+  Lbzu,
+  Lbzux,
+  Lbzx,
+  Lha,
+  Lhau,
+  Lhaux,
+  Lhax,
+  Lhz,
+  Lhzu,
+  Lhzux,
+  Lhzx,
+  Lwz,
+  Lwzu,
+  Lwzux,
+  Lwzx,
+  Stb,
+  Stbu,
+  Stbux,
+  Stbx,
+  Sth,
+  Sthu,
+  Sthux,
+  Sthx,
+  Stw,
+  Stwu,
+  Stwux,
+  Stwx,
+  Lhbrx,
+  Lwbrx,
+  Sthbrx,
+  Stwbrx,
+  Lmw,
+  Stmw,
+  Lswi,
+  Lswx,
+  Stswi,
+  Stswx,
+  Eieio,
+  Isync,
+  Lwarx,
+  StwcxDot,
+  Sync,
+  Lfd,
+  Lfdu,
+  Lfdux,
+  Lfdx,
+  Lfs,
+  Lfsu,
+  Lfsux,
+  Lfsx,
+  Stfd,
+  Stfdu,
+  Stfdux,
+  Stfdx,
+  Stfiwx,
+  Stfs,
+  Stfsu,
+  Stfsux,
+  Stfsx,
+  Fabs,
+  Fmr,
+  Fnabs,
+  Fneg,
+  B,
+  Bc,
+  Bcctr,
+  Bclr,
+  Crand,
+  Crandc,
+  Creqv,
+  Crnand,
+  Crnor,
+  Cror,
+  Crorc,
+  Crxor,
+  Mcrf,
+  Rfi,
+  Sc,
+  Tw,
+  Twi,
+  Mcrxr,
+  Mfcr,
+  Mfmsr,
+  Mfspr_nobitswap,
+  Mftb_nobitswap,
+  Mtcrf,
+  Mtmsr,
+  Mtspr_nobitswap,
+  Dcbf,
+  Dcbi,
+  Dcbst,
+  Dcbt,
+  Dcbtst,
+  Dcbz,
+  Icbi,
+  Mfsr,
+  Mfsrin,
+  Mtsr,
+  Mtsrin,
+  Tlbie,
+  Tlbsync,
+  Eciwx,
+  Ecowx,
+  Psq_lx,
+  Psq_stx,
+  Psq_lux,
+  Psq_stux,
+  Psq_l,
+  Psq_lu,
+  Psq_st,
+  Psq_stu,
+  Ps_div,
+  Ps_sub,
+  Ps_add,
+  Ps_sel,
+  Ps_res,
+  Ps_mul,
+  Ps_rsqrte,
+  Ps_msub,
+  Ps_madd,
+  Ps_nmsub,
+  Ps_nmadd,
+  Ps_neg,
+  Ps_mr,
+  Ps_nabs,
+  Ps_abs,
+  Ps_sum0,
+  Ps_sum1,
+  Ps_muls0,
+  Ps_muls1,
+  Ps_madds0,
+  Ps_madds1,
+  Ps_cmpu0,
+  Ps_cmpo0,
+  Ps_cmpu1,
+  Ps_cmpo1,
+  Ps_merge00,
+  Ps_merge01,
+  Ps_merge10,
+  Ps_merge11,
+  Dcbz_l,
+  LastMnemonic = Dcbz_l,
+  InvalidMnemonic,
+};
+
+enum class ExtendedGekkoMnemonic : size_t
+{
+  Subi,
+  Subis,
+  Subic,
+  SubicDot,
+  Sub,
+  Subc,
+  Cmpwi,
+  Cmpw,
+  Cmplwi,
+  Cmplw,
+  Extlwi,
+  Extrwi,
+  Inslwi,
+  Insrwi,
+  Rotlwi,
+  Rotrwi,
+  Rotlw,
+  Slwi,
+  Srwi,
+  Clrlwi,
+  Clrrwi,
+  Clrlslwi,
+  Bt,
+  Bf,
+  Bdnz,
+  Bdnzt,
+  Bdnzf,
+  Bdz,
+  Bdzt,
+  Bdzf,
+  BtPredict,
+  BfPredict,
+  BdnzPredict,
+  BdnztPredict,
+  BdnzfPredict,
+  BdzPredict,
+  BdztPredict,
+  BdzfPredict,
+  Blr,
+  Btlr,
+  Bflr,
+  Bdnzlr,
+  Bdnztlr,
+  Bdnzflr,
+  Bdzlr,
+  Bdztlr,
+  Bdzflr,
+  BtlrPredict,
+  BflrPredict,
+  BdnzlrPredict,
+  BdnztlrPredict,
+  BdnzflrPredict,
+  BdzlrPredict,
+  BdztlrPredict,
+  BdzflrPredict,
+  Bctr,
+  Btctr,
+  Bfctr,
+  BtctrPredict,
+  BfctrPredict,
+  Blt,
+  Ble,
+  Beq,
+  Bge,
+  Bgt,
+  Bnl,
+  Bne,
+  Bng,
+  Bso,
+  Bns,
+  Bun,
+  Bnu,
+  BltPredict,
+  BlePredict,
+  BeqPredict,
+  BgePredict,
+  BgtPredict,
+  BnlPredict,
+  BnePredict,
+  BngPredict,
+  BsoPredict,
+  BnsPredict,
+  BunPredict,
+  BnuPredict,
+  Bltlr,
+  Blelr,
+  Beqlr,
+  Bgelr,
+  Bgtlr,
+  Bnllr,
+  Bnelr,
+  Bnglr,
+  Bsolr,
+  Bnslr,
+  Bunlr,
+  Bnulr,
+  BltlrPredict,
+  BlelrPredict,
+  BeqlrPredict,
+  BgelrPredict,
+  BgtlrPredict,
+  BnllrPredict,
+  BnelrPredict,
+  BnglrPredict,
+  BsolrPredict,
+  BnslrPredict,
+  BunlrPredict,
+  BnulrPredict,
+  Bltctr,
+  Blectr,
+  Beqctr,
+  Bgectr,
+  Bgtctr,
+  Bnlctr,
+  Bnectr,
+  Bngctr,
+  Bsoctr,
+  Bnsctr,
+  Bunctr,
+  Bnuctr,
+  BltctrPredict,
+  BlectrPredict,
+  BeqctrPredict,
+  BgectrPredict,
+  BgtctrPredict,
+  BnlctrPredict,
+  BnectrPredict,
+  BngctrPredict,
+  BsoctrPredict,
+  BnsctrPredict,
+  BunctrPredict,
+  BnuctrPredict,
+  Crset,
+  Crclr,
+  Crmove,
+  Crnot,
+  Twlt,
+  Twlti,
+  Twle,
+  Twlei,
+  Tweq,
+  Tweqi,
+  Twge,
+  Twgei,
+  Twgt,
+  Twgti,
+  Twnl,
+  Twnli,
+  Twne,
+  Twnei,
+  Twng,
+  Twngi,
+  Twllt,
+  Twllti,
+  Twlle,
+  Twllei,
+  Twlge,
+  Twlgei,
+  Twlgt,
+  Twlgti,
+  Twlnl,
+  Twlnli,
+  Twlng,
+  Twlngi,
+  Trap,
+  Mtxer,
+  Mfxer,
+  Mtlr,
+  Mflr,
+  Mtctr,
+  Mfctr,
+  Mtdsisr,
+  Mfdsisr,
+  Mtdar,
+  Mfdar,
+  Mtdec,
+  Mfdec,
+  Mtsdr1,
+  Mfsdr1,
+  Mtsrr0,
+  Mfsrr0,
+  Mtsrr1,
+  Mfsrr1,
+  Mtasr,
+  Mfasr,
+  Mtear,
+  Mfear,
+  Mttbl,
+  Mftbl,
+  Mttbu,
+  Mftbu,
+  Mtsprg,
+  Mfsprg,
+  Mtibatu,
+  Mfibatu,
+  Mtibatl,
+  Mfibatl,
+  Mtdbatu,
+  Mfdbatu,
+  Mtdbatl,
+  Mfdbatl,
+  Nop,
+  Li,
+  Lis,
+  La,
+  Mr,
+  Not,
+  Mtcr,
+  Mfspr,
+  Mftb,
+  Mtspr,
+  LastMnemonic = Mtspr,
+  InvalidMnemonic
+};
+}  // namespace Common::GekkoAssembler

Source/Core/Common/Assembler/AssemblerTables.h

@@ -0,0 +1,152 @@
+// Copyright 2023 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <array>
+#include <cstddef>
+#include <optional>
+#include <string_view>
+#include <vector>
+
+#include "Common/Assembler/AssemblerShared.h"
+#include "Common/Assembler/CaseInsensitiveDict.h"
+#include "Common/CommonTypes.h"
+
+namespace Common::GekkoAssembler::detail
+{
+///////////////////
+// PARSER TABLES //
+///////////////////
+enum class ParseAlg
+{
+  None,
+  Op1,
+  NoneOrOp1,
+  Op1Off1,
+  Op2,
+  Op1Or2,
+  Op3,
+  Op2Or3,
+  Op4,
+  Op5,
+  Op1Off1Op2,
+};
+
+struct ParseInfo
+{
+  size_t mnemonic_index;
+  ParseAlg parse_algorithm;
+};
+
+// Mapping of SPRG names to values
+extern const CaseInsensitiveDict<u32, '_'> sprg_map;
+// Mapping of directive names to an enumeration
+extern const CaseInsensitiveDict<GekkoDirective> directives_map;
+// Mapping of normal Gekko mnemonics to their index and argument form
+extern const CaseInsensitiveDict<ParseInfo, '.', '_'> mnemonic_tokens;
+// Mapping of extended Gekko mnemonics to their index and argument form
+extern const CaseInsensitiveDict<ParseInfo, '.', '_', '+', '-'> extended_mnemonic_tokens;
+
+//////////////////////
+// ASSEMBLER TABLES //
+//////////////////////
+constexpr size_t MAX_OPERANDS = 5;
+
+struct OperandList
+{
+  std::array<Tagged<Interval, u32>, MAX_OPERANDS> list;
+  u32 count;
+  bool overfill;
+
+  constexpr u32 operator[](size_t index) const { return ValueOf(list[index]); }
+  constexpr u32& operator[](size_t index) { return ValueOf(list[index]); }
+
+  void Insert(size_t before, u32 val);
+
+  template <typename It>
+  void Copy(It begin, It end)
+  {
+    count = 0;
+    for (auto& i : list)
+    {
+      if (begin == end)
+      {
+        break;
+      }
+      i = *begin;
+      begin++;
+      count++;
+    }
+    overfill = begin != end;
+  }
+};
+
+struct OperandDesc
+{
+  u32 mask;
+  struct
+  {
+    u32 shift : 31;
+    bool is_signed : 1;
+  };
+  u32 MaxVal() const;
+  u32 MinVal() const;
+  u32 TruncBits() const;
+
+  bool Fits(u32 val) const;
+  u32 Fit(u32 val) const;
+};
+
+// MnemonicDesc holds the machine-code template for mnemonics
+struct MnemonicDesc
+{
+  // Initial value for a given mnemonic (opcode, func code, LK, AA, OE)
+  const u32 initial_value;
+  const u32 operand_count;
+  // Masks for operands
+  std::array<OperandDesc, MAX_OPERANDS> operand_masks;
+};
+
+// ExtendedMnemonicDesc holds the name of the mnemonic it transforms to as well as a
+// transformer callback to translate the operands into the correct form for the base mnemonic
+struct ExtendedMnemonicDesc
+{
+  size_t mnemonic_index;
+  void (*transform_operands)(OperandList&);
+};
+
+static constexpr size_t NUM_MNEMONICS = static_cast<size_t>(GekkoMnemonic::LastMnemonic) + 1;
+static constexpr size_t NUM_EXT_MNEMONICS =
+    static_cast<size_t>(ExtendedGekkoMnemonic::LastMnemonic) + 1;
+static constexpr size_t VARIANT_PERMUTATIONS = 4;
+
+// Table for mapping mnemonic+variants to their descriptors
+extern const std::array<MnemonicDesc, NUM_MNEMONICS * VARIANT_PERMUTATIONS> mnemonics;
+// Table for mapping extended mnemonic+variants to their descriptors
+extern const std::array<ExtendedMnemonicDesc, NUM_EXT_MNEMONICS * VARIANT_PERMUTATIONS>
+    extended_mnemonics;
+
+//////////////////
+// LEXER TABLES //
+//////////////////
+
+// In place of the reliace on std::regex, DFAs will be defined for matching sufficiently complex
+// tokens This gives an extra benefit of providing reasons for match failures
+using TransitionF = bool (*)(char c);
+using DfaEdge = std::pair<TransitionF, size_t>;
+struct DfaNode
+{
+  std::vector<DfaEdge> edges;
+  // If nullopt: this is a final node
+  // If string: invalid reason
+  std::optional<std::string_view> match_failure_reason;
+};
+
+// Floating point strings that will be accepted by std::stof/std::stod
+// regex: [\+-]?(\d+(\.\d+)?|\.\d+)(e[\+-]?\d+)?
+extern const std::vector<DfaNode> float_dfa;
+// C-style strings
+// regex: "([^\\\n]|\\([0-7]{1,3}|x[0-9a-fA-F]+|[^x0-7\n]))*"
+extern const std::vector<DfaNode> string_dfa;
+}  // namespace Common::GekkoAssembler::detail

Source/Core/Common/Assembler/CaseInsensitiveDict.h

@@ -0,0 +1,126 @@
+// Copyright 2023 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <array>
+#include <optional>
+#include <string>
+#include <string_view>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+namespace Common::GekkoAssembler::detail
+{
+// Hacky implementation of a case insensitive alphanumeric trie supporting extended entries
+// Standing in for std::map to support case-insensitive lookups while allowing string_views in
+// lookups
+template <typename V, char... ExtraMatches>
+class CaseInsensitiveDict
+{
+public:
+  CaseInsensitiveDict(const std::initializer_list<std::pair<std::string_view, V>>& il)
+  {
+    for (auto&& [k, v] : il)
+    {
+      Add(k, v);
+    }
+  }
+
+  template <typename T>
+  V const* Find(const T& key) const
+  {
+    auto&& [last_e, it] = TryFind(key);
+    if (it == key.cend() && last_e->_val)
+    {
+      return &*last_e->_val;
+    }
+    return nullptr;
+  }
+  static constexpr size_t NUM_CONNS = 36 + sizeof...(ExtraMatches);
+  static constexpr uint32_t INVALID_CONN = static_cast<uint32_t>(-1);
+
+private:
+  struct TrieEntry
+  {
+    std::array<uint32_t, 36 + sizeof...(ExtraMatches)> _conns;
+    std::optional<V> _val;
+
+    TrieEntry() { std::fill(_conns.begin(), _conns.end(), INVALID_CONN); }
+  };
+
+  constexpr size_t IndexOf(char c) const
+  {
+    size_t idx;
+    if (std::isalpha(c))
+    {
+      idx = std::tolower(c) - 'a';
+    }
+    else if (std::isdigit(c))
+    {
+      idx = c - '0' + 26;
+    }
+    else
+    {
+      idx = 36;
+      // Expands to an equivalent for loop over ExtraMatches
+      if constexpr (sizeof...(ExtraMatches) > 0)
+      {
+        (void)((c != ExtraMatches ? ++idx, true : false) && ...);
+      }
+    }
+    return idx;
+  }
+
+  template <typename T>
+  auto TryFind(const T& key) const -> std::pair<TrieEntry const*, decltype(key.cbegin())>
+  {
+    std::pair<TrieEntry const*, decltype(key.cbegin())> ret(&m_root_entry, key.cbegin());
+    const auto k_end = key.cend();
+
+    for (; ret.second != k_end; ret.second++)
+    {
+      const size_t idx = IndexOf(*ret.second);
+      if (idx >= NUM_CONNS || ret.first->_conns[idx] == INVALID_CONN)
+      {
+        break;
+      }
+
+      ret.first = &m_entry_pool[ret.first->_conns[idx]];
+    }
+
+    return ret;
+  }
+
+  template <typename T>
+  auto TryFind(const T& key) -> std::pair<TrieEntry*, decltype(key.cbegin())>
+  {
+    auto&& [e_const, it] =
+        const_cast<CaseInsensitiveDict<V, ExtraMatches...> const*>(this)->TryFind(key);
+    return {const_cast<TrieEntry*>(e_const), it};
+  }
+
+  void Add(std::string_view key, const V& val)
+  {
+    auto&& [last_e, it] = TryFind(key);
+    if (it != key.cend())
+    {
+      for (; it != key.cend(); it++)
+      {
+        const size_t idx = IndexOf(*it);
+        if (idx >= NUM_CONNS)
+        {
+          break;
+        }
+        last_e->_conns[idx] = static_cast<uint32_t>(m_entry_pool.size());
+        last_e = &m_entry_pool.emplace_back();
+      }
+    }
+    last_e->_val = val;
+  }
+
+  TrieEntry m_root_entry;
+  std::vector<TrieEntry> m_entry_pool;
+};
+}  // namespace Common::GekkoAssembler::detail

Source/Core/Common/Assembler/GekkoAssembler.cpp

@@ -0,0 +1,189 @@
+// Copyright 2023 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "Common/Assembler/GekkoAssembler.h"
+
+#include <algorithm>
+#include <array>
+#include <string>
+#include <vector>
+
+#include <fmt/format.h>
+
+#include "Common/Assembler/AssemblerShared.h"
+#include "Common/Assembler/AssemblerTables.h"
+#include "Common/Assembler/GekkoIRGen.h"
+#include "Common/Assert.h"
+#include "Common/CommonTypes.h"
+
+namespace Common::GekkoAssembler
+{
+namespace
+{
+using namespace Common::GekkoAssembler::detail;
+
+FailureOr<u32> FillInstruction(const MnemonicDesc& desc, const OperandList& operands,
+                               std::string_view inst_line)
+{
+  // Parser shouldn't allow this to pass
+  ASSERT_MSG(COMMON, desc.operand_count == operands.count && !operands.overfill,
+             "Unexpected operand count mismatch for instruction {}. Expected {} but found {}",
+             inst_line, desc.operand_count, operands.overfill ? 6 : operands.count);
+
+  u32 instruction = desc.initial_value;
+  for (u32 i = 0; i < operands.count; i++)
+  {
+    if (!desc.operand_masks[i].Fits(operands[i]))
+    {
+      std::string message;
+      const u32 trunc_bits = desc.operand_masks[i].TruncBits();
+      if (trunc_bits == 0)
+      {
+        if (desc.operand_masks[i].is_signed)
+        {
+          message = fmt::format("{:#x} not between {:#x} and {:#x}", static_cast<s32>(operands[i]),
+                                static_cast<s32>(desc.operand_masks[i].MinVal()),
+                                static_cast<s32>(desc.operand_masks[i].MaxVal()));
+        }
+        else
+        {
+          message = fmt::format("{:#x} not between {:#x} and {:#x}", operands[i],
+                                desc.operand_masks[i].MinVal(), desc.operand_masks[i].MaxVal());
+        }
+      }
+      else
+      {
+        if (desc.operand_masks[i].is_signed)
+        {
+          message = fmt::format("{:#x} not between {:#x} and {:#x} or not aligned to {}",
+                                static_cast<s32>(operands[i]),
+                                static_cast<s32>(desc.operand_masks[i].MinVal()),
+                                static_cast<s32>(desc.operand_masks[i].MaxVal()), trunc_bits + 1);
+        }
+        else
+        {
+          message = fmt::format("{:#x} not between {:#x} and {:#x} or not aligned to {}",
+                                operands[i], desc.operand_masks[i].MinVal(),
+                                desc.operand_masks[i].MaxVal(), trunc_bits + 1);
+        }
+      }
+      return AssemblerError{std::move(message), "", 0, TagOf(operands.list[i]).begin,
+                            TagOf(operands.list[i]).len};
+    }
+    instruction |= desc.operand_masks[i].Fit(operands[i]);
+  }
+  return instruction;
+}
+
+void AdjustOperandsForGas(GekkoMnemonic mnemonic, OperandList& ops_list)
+{
+  switch (mnemonic)
+  {
+  case GekkoMnemonic::Cmp:
+  case GekkoMnemonic::Cmpl:
+  case GekkoMnemonic::Cmpi:
+  case GekkoMnemonic::Cmpli:
+    if (ops_list.count < 4)
+    {
+      ops_list.Insert(0, 0);
+    }
+    break;
+
+  case GekkoMnemonic::Addis:
+    // Because GAS wants to allow for addis and lis to work nice with absolute addresses, the
+    // immediate operand should also "fit" into the _UIMM field, so just turn a valid UIMM into a
+    // SIMM
+    if (ops_list[2] >= 0x8000 && ops_list[2] <= 0xffff)
+    {
+      ops_list[2] = ops_list[2] - 0x10000;
+    }
+    break;
+
+  default:
+    break;
+  }
+}
+
+}  // namespace
+
+void CodeBlock::PushBigEndian(u32 val)
+{
+  instructions.push_back((val >> 24) & 0xff);
+  instructions.push_back((val >> 16) & 0xff);
+  instructions.push_back((val >> 8) & 0xff);
+  instructions.push_back(val & 0xff);
+}
+
+FailureOr<std::vector<CodeBlock>> Assemble(std::string_view instruction,
+                                           u32 current_instruction_address)
+{
+  FailureOr<detail::GekkoIR> parse_result =
+      detail::ParseToIR(instruction, current_instruction_address);
+  if (IsFailure(parse_result))
+  {
+    return GetFailure(parse_result);
+  }
+
+  const auto& parsed_blocks = GetT(parse_result).blocks;
+  const auto& operands = GetT(parse_result).operand_pool;
+  std::vector<CodeBlock> out_blocks;
+
+  for (const detail::IRBlock& parsed_block : parsed_blocks)
+  {
+    CodeBlock new_block(parsed_block.block_address);
+    for (const detail::ChunkVariant& chunk : parsed_block.chunks)
+    {
+      if (std::holds_alternative<detail::InstChunk>(chunk))
+      {
+        for (const detail::GekkoInstruction& parsed_inst : std::get<detail::InstChunk>(chunk))
+        {
+          OperandList adjusted_ops;
+          ASSERT(parsed_inst.op_interval.len <= MAX_OPERANDS);
+          adjusted_ops.Copy(operands.begin() + parsed_inst.op_interval.begin,
+                            operands.begin() + parsed_inst.op_interval.End());
+
+          size_t idx = parsed_inst.mnemonic_index;
+          if (parsed_inst.is_extended)
+          {
+            extended_mnemonics[idx].transform_operands(adjusted_ops);
+            idx = extended_mnemonics[idx].mnemonic_index;
+          }
+
+          AdjustOperandsForGas(static_cast<GekkoMnemonic>(idx >> 2), adjusted_ops);
+
+          FailureOr<u32> inst = FillInstruction(mnemonics[idx], adjusted_ops, parsed_inst.raw_text);
+          if (IsFailure(inst))
+          {
+            GetFailure(inst).error_line = parsed_inst.raw_text;
+            GetFailure(inst).line = parsed_inst.line_number;
+            return GetFailure(inst);
+          }
+
+          new_block.PushBigEndian(GetT(inst));
+        }
+      }
+      else if (std::holds_alternative<detail::ByteChunk>(chunk))
+      {
+        detail::ByteChunk byte_arr = std::get<detail::ByteChunk>(chunk);
+        new_block.instructions.insert(new_block.instructions.end(), byte_arr.begin(),
+                                      byte_arr.end());
+      }
+      else if (std::holds_alternative<detail::PadChunk>(chunk))
+      {
+        detail::PadChunk pad_len = std::get<detail::PadChunk>(chunk);
+        new_block.instructions.insert(new_block.instructions.end(), pad_len, 0);
+      }
+      else
+      {
+        ASSERT(false);
+      }
+    }
+
+    if (!new_block.instructions.empty())
+    {
+      out_blocks.emplace_back(std::move(new_block));
+    }
+  }
+  return out_blocks;
+}
+}  // namespace Common::GekkoAssembler

Source/Core/Common/Assembler/GekkoAssembler.h

@@ -0,0 +1,29 @@
+// Copyright 2023 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <string_view>
+#include <vector>
+
+#include "Common/Assembler/AssemblerShared.h"
+#include "Common/CommonTypes.h"
+
+namespace Common::GekkoAssembler
+{
+struct CodeBlock
+{
+  CodeBlock(u32 address) : block_address(address) {}
+
+  void PushBigEndian(u32 val);
+
+  u32 block_address;
+  std::vector<u8> instructions;
+};
+
+// Common::GekkoAssember::Assemble - Core routine for assembling Gekko/Broadway instructions
+// Supports the full Gekko ISA, as well as the extended mnemonics defined by the book "PowerPC
+// Microprocessor Family: The Programming Environments" The input assembly is fully parsed and
+// assembled with a base address specified by the base_virtual_address
+FailureOr<std::vector<CodeBlock>> Assemble(std::string_view assembly, u32 base_virtual_address);
+}  // namespace Common::GekkoAssembler

Source/Core/Common/Assembler/GekkoIRGen.cpp

@@ -0,0 +1,832 @@
+// Copyright 2023 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "Common/Assembler/GekkoIRGen.h"
+
+#include <functional>
+#include <map>
+#include <numeric>
+#include <set>
+#include <stack>
+#include <variant>
+#include <vector>
+
+#include <fmt/format.h>
+
+#include "Common/Assembler/AssemblerShared.h"
+#include "Common/Assembler/GekkoParser.h"
+#include "Common/Assert.h"
+#include "Common/BitUtils.h"
+
+namespace Common::GekkoAssembler::detail
+{
+namespace
+{
+class GekkoIRPlugin : public ParsePlugin
+{
+public:
+  GekkoIRPlugin(GekkoIR& result, u32 base_addr)
+      : m_output_result(result), m_active_var(nullptr), m_operand_scan_begin(0)
+  {
+    m_active_block = &m_output_result.blocks.emplace_back(base_addr);
+  }
+  virtual ~GekkoIRPlugin() = default;
+
+  void OnDirectivePre(GekkoDirective directive) override;
+  void OnDirectivePost(GekkoDirective directive) override;
+  void OnInstructionPre(const ParseInfo& mnemonic_info, bool extended) override;
+  void OnInstructionPost(const ParseInfo& mnemonic_info, bool extended) override;
+  void OnOperandPre() override;
+  void OnOperandPost() override;
+  void OnResolvedExprPost() override;
+  void OnOperator(AsmOp operation) override;
+  void OnTerminal(Terminal type, const AssemblerToken& val) override;
+  void OnHiaddr(std::string_view id) override;
+  void OnLoaddr(std::string_view id) override;
+  void OnCloseParen(ParenType type) override;
+  void OnLabelDecl(std::string_view name) override;
+  void OnVarDecl(std::string_view name) override;
+  void PostParseAction() override;
+
+  u32 CurrentAddress() const;
+  std::optional<u64> LookupVar(std::string_view lab);
+  std::optional<u32> LookupLabel(std::string_view lab);
+
+  template <typename T>
+  T& GetChunk();
+
+  template <typename T>
+  void AddBytes(T val);
+
+  void AddStringBytes(std::string_view str, bool null_term);
+
+  void PadAlign(u32 bits);
+  void PadSpace(size_t space);
+
+  void StartBlock(u32 address);
+  void StartBlockAlign(u32 bits);
+  void StartInstruction(size_t mnemonic_index, bool extended);
+  void FinishInstruction();
+  void SaveOperandFixup(size_t str_left, size_t str_right);
+
+  void AddBinaryEvaluator(u32 (*evaluator)(u32, u32));
+  void AddUnaryEvaluator(u32 (*evaluator)(u32));
+  void AddAbsoluteAddressConv();
+  void AddLiteral(u32 lit);
+  void AddSymbolResolve(std::string_view sym, bool absolute);
+
+  void RunFixups();
+
+  void EvalOperatorRel(AsmOp operation);
+  void EvalOperatorAbs(AsmOp operation);
+  void EvalTerminalRel(Terminal type, const AssemblerToken& tok);
+  void EvalTerminalAbs(Terminal type, const AssemblerToken& tok);
+
+private:
+  enum class EvalMode
+  {
+    RelAddrDoublePass,
+    AbsAddrSinglePass,
+  };
+
+  GekkoIR& m_output_result;
+
+  IRBlock* m_active_block;
+  GekkoInstruction m_build_inst;
+  u64* m_active_var;
+  size_t m_operand_scan_begin;
+
+  std::map<std::string, u32, std::less<>> m_labels;
+  std::map<std::string, u64, std::less<>> m_constants;
+  std::set<std::string> m_symset;
+
+  EvalMode m_evaluation_mode;
+
+  // For operand parsing
+  std::stack<std::function<u32()>> m_fixup_stack;
+  std::vector<std::function<u32()>> m_operand_fixups;
+  size_t m_operand_str_start;
+
+  // For directive parsing
+  std::vector<u64> m_eval_stack;
+  std::variant<std::vector<float>, std::vector<double>> m_floats_list;
+  std::string_view m_string_lit;
+  GekkoDirective m_active_directive;
+};
+
+///////////////
+// OVERRIDES //
+///////////////
+
+void GekkoIRPlugin::OnDirectivePre(GekkoDirective directive)
+{
+  m_evaluation_mode = EvalMode::AbsAddrSinglePass;
+  m_active_directive = directive;
+  m_eval_stack = std::vector<u64>{};
+
+  switch (directive)
+  {
+  case GekkoDirective::Float:
+    m_floats_list = std::vector<float>{};
+    break;
+  case GekkoDirective::Double:
+    m_floats_list = std::vector<double>{};
+    break;
+  default:
+    break;
+  }
+}
+
+void GekkoIRPlugin::OnDirectivePost(GekkoDirective directive)
+{
+  switch (directive)
+  {
+  // .nbyte directives are handled by OnResolvedExprPost
+  default:
+    break;
+
+  case GekkoDirective::Float:
+  case GekkoDirective::Double:
+    std::visit(
+        [this](auto&& vec) {
+          for (auto&& val : vec)
+          {
+            AddBytes(val);
+          }
+        },
+        m_floats_list);
+    break;
+
+  case GekkoDirective::DefVar:
+    ASSERT(m_active_var != nullptr);
+    *m_active_var = m_eval_stack.back();
+    m_active_var = nullptr;
+    break;
+
+  case GekkoDirective::Locate:
+    StartBlock(static_cast<u32>(m_eval_stack.back()));
+    break;
+
+  case GekkoDirective::Zeros:
+    PadSpace(static_cast<u32>(m_eval_stack.back()));
+    break;
+
+  case GekkoDirective::Skip:
+  {
+    const u32 skip_len = static_cast<u32>(m_eval_stack.back());
+    if (skip_len > 0)
+    {
+      StartBlock(CurrentAddress() + skip_len);
+    }
+    break;
+  }
+
+  case GekkoDirective::PadAlign:
+    PadAlign(static_cast<u32>(m_eval_stack.back()));
+    break;
+
+  case GekkoDirective::Align:
+    StartBlockAlign(static_cast<u32>(m_eval_stack.back()));
+    break;
+
+  case GekkoDirective::Ascii:
+    AddStringBytes(m_string_lit, false);
+    break;
+
+  case GekkoDirective::Asciz:
+    AddStringBytes(m_string_lit, true);
+    break;
+  }
+  m_eval_stack = {};
+}
+
+void GekkoIRPlugin::OnInstructionPre(const ParseInfo& mnemonic_info, bool extended)
+{
+  m_evaluation_mode = EvalMode::RelAddrDoublePass;
+  StartInstruction(mnemonic_info.mnemonic_index, extended);
+}
+
+void GekkoIRPlugin::OnInstructionPost(const ParseInfo&, bool)
+{
+  FinishInstruction();
+}
+
+void GekkoIRPlugin::OnOperandPre()
+{
+  m_operand_str_start = m_owner->lexer.ColNumber();
+}
+
+void GekkoIRPlugin::OnOperandPost()
+{
+  SaveOperandFixup(m_operand_str_start, m_owner->lexer.ColNumber());
+}
+
+void GekkoIRPlugin::OnResolvedExprPost()
+{
+  switch (m_active_directive)
+  {
+  case GekkoDirective::Byte:
+    AddBytes<u8>(static_cast<u8>(m_eval_stack.back()));
+    break;
+  case GekkoDirective::_2byte:
+    AddBytes<u16>(static_cast<u16>(m_eval_stack.back()));
+    break;
+  case GekkoDirective::_4byte:
+    AddBytes<u32>(static_cast<u32>(m_eval_stack.back()));
+    break;
+  case GekkoDirective::_8byte:
+    AddBytes<u64>(static_cast<u64>(m_eval_stack.back()));
+    break;
+  default:
+    return;
+  }
+  m_eval_stack.clear();
+}
+
+void GekkoIRPlugin::OnOperator(AsmOp operation)
+{
+  if (m_evaluation_mode == EvalMode::RelAddrDoublePass)
+  {
+    EvalOperatorRel(operation);
+  }
+  else
+  {
+    EvalOperatorAbs(operation);
+  }
+}
+
+void GekkoIRPlugin::OnTerminal(Terminal type, const AssemblerToken& val)
+{
+  if (type == Terminal::Str)
+  {
+    m_string_lit = val.token_val;
+  }
+  else if (m_evaluation_mode == EvalMode::RelAddrDoublePass)
+  {
+    EvalTerminalRel(type, val);
+  }
+  else
+  {
+    EvalTerminalAbs(type, val);
+  }
+}
+
+void GekkoIRPlugin::OnHiaddr(std::string_view id)
+{
+  if (m_evaluation_mode == EvalMode::RelAddrDoublePass)
+  {
+    AddSymbolResolve(id, true);
+    AddLiteral(16);
+    AddBinaryEvaluator([](u32 lhs, u32 rhs) { return lhs >> rhs; });
+    AddLiteral(0xffff);
+    AddBinaryEvaluator([](u32 lhs, u32 rhs) { return lhs & rhs; });
+  }
+  else
+  {
+    u32 base;
+    if (auto lbl = LookupLabel(id); lbl)
+    {
+      base = *lbl;
+    }
+    else if (auto var = LookupVar(id); var)
+    {
+      base = *var;
+    }
+    else
+    {
+      m_owner->EmitErrorHere(fmt::format("Undefined reference to Label/Constant '{}'", id));
+      return;
+    }
+    m_eval_stack.push_back((base >> 16) & 0xffff);
+  }
+}
+
+void GekkoIRPlugin::OnLoaddr(std::string_view id)
+{
+  if (m_evaluation_mode == EvalMode::RelAddrDoublePass)
+  {
+    AddSymbolResolve(id, true);
+    AddLiteral(0xffff);
+    AddBinaryEvaluator([](u32 lhs, u32 rhs) { return lhs & rhs; });
+  }
+  else
+  {
+    u32 base;
+    if (auto lbl = LookupLabel(id); lbl)
+    {
+      base = *lbl;
+    }
+    else if (auto var = LookupVar(id); var)
+    {
+      base = *var;
+    }
+    else
+    {
+      m_owner->EmitErrorHere(fmt::format("Undefined reference to Label/Constant '{}'", id));
+      return;
+    }
+
+    m_eval_stack.push_back(base & 0xffff);
+  }
+}
+
+void GekkoIRPlugin::OnCloseParen(ParenType type)
+{
+  if (type != ParenType::RelConv)
+  {
+    return;
+  }
+
+  if (m_evaluation_mode == EvalMode::RelAddrDoublePass)
+  {
+    AddAbsoluteAddressConv();
+  }
+  else
+  {
+    m_eval_stack.push_back(CurrentAddress());
+    EvalOperatorAbs(AsmOp::Sub);
+  }
+}
+
+void GekkoIRPlugin::OnLabelDecl(std::string_view name)
+{
+  const std::string name_str(name);
+  if (m_symset.contains(name_str))
+  {
+    m_owner->EmitErrorHere(fmt::format("Label/Constant {} is already defined", name));
+    return;
+  }
+
+  m_labels[name_str] = m_active_block->BlockEndAddress();
+  m_symset.insert(name_str);
+}
+
+void GekkoIRPlugin::OnVarDecl(std::string_view name)
+{
+  const std::string name_str(name);
+  if (m_symset.contains(name_str))
+  {
+    m_owner->EmitErrorHere(fmt::format("Label/Constant {} is already defined", name));
+    return;
+  }
+
+  m_active_var = &m_constants[name_str];
+  m_symset.insert(name_str);
+}
+
+void GekkoIRPlugin::PostParseAction()
+{
+  RunFixups();
+}
+
+//////////////////////
+// HELPER FUNCTIONS //
+//////////////////////
+
+u32 GekkoIRPlugin::CurrentAddress() const
+{
+  return m_active_block->BlockEndAddress();
+}
+
+std::optional<u64> GekkoIRPlugin::LookupVar(std::string_view var)
+{
+  auto var_it = m_constants.find(var);
+  return var_it == m_constants.end() ? std::nullopt : std::optional(var_it->second);
+}
+
+std::optional<u32> GekkoIRPlugin::LookupLabel(std::string_view lab)
+{
+  auto label_it = m_labels.find(lab);
+  return label_it == m_labels.end() ? std::nullopt : std::optional(label_it->second);
+}
+
+void GekkoIRPlugin::AddStringBytes(std::string_view str, bool null_term)
+{
+  ByteChunk& bytes = GetChunk<ByteChunk>();
+  ConvertStringLiteral(str, &bytes);
+  if (null_term)
+  {
+    bytes.push_back('\0');
+  }
+}
+
+template <typename T>
+T& GekkoIRPlugin::GetChunk()
+{
+  if (!m_active_block->chunks.empty() && std::holds_alternative<T>(m_active_block->chunks.back()))
+  {
+    return std::get<T>(m_active_block->chunks.back());
+  }
+
+  return std::get<T>(m_active_block->chunks.emplace_back(T{}));
+}
+
+template <typename T>
+void GekkoIRPlugin::AddBytes(T val)
+{
+  if constexpr (std::is_integral_v<T>)
+  {
+    ByteChunk& bytes = GetChunk<ByteChunk>();
+    for (size_t i = sizeof(T) - 1; i > 0; i--)
+    {
+      bytes.push_back((val >> (8 * i)) & 0xff);
+    }
+    bytes.push_back(val & 0xff);
+  }
+  else if constexpr (std::is_same_v<T, float>)
+  {
+    static_assert(sizeof(double) == sizeof(u64));
+    AddBytes(BitCast<u32>(val));
+  }
+  else
+  {
+    // std::is_same_v<T, double>
+    static_assert(sizeof(double) == sizeof(u64));
+    AddBytes(BitCast<u64>(val));
+  }
+}
+
+void GekkoIRPlugin::PadAlign(u32 bits)
+{
+  const u32 align_mask = (1 << bits) - 1;
+  const u32 current_addr = m_active_block->BlockEndAddress();
+  if (current_addr & align_mask)
+  {
+    PadChunk& current_pad = GetChunk<PadChunk>();
+    current_pad += (1 << bits) - (current_addr & align_mask);
+  }
+}
+
+void GekkoIRPlugin::PadSpace(size_t space)
+{
+  GetChunk<PadChunk>() += space;
+}
+
+void GekkoIRPlugin::StartBlock(u32 address)
+{
+  m_active_block = &m_output_result.blocks.emplace_back(address);
+}
+
+void GekkoIRPlugin::StartBlockAlign(u32 bits)
+{
+  const u32 align_mask = (1 << bits) - 1;
+  const u32 current_addr = m_active_block->BlockEndAddress();
+  if (current_addr & align_mask)
+  {
+    StartBlock((1 << bits) + (current_addr & ~align_mask));
+  }
+}
+
+void GekkoIRPlugin::StartInstruction(size_t mnemonic_index, bool extended)
+{
+  m_build_inst = GekkoInstruction{
+      .mnemonic_index = mnemonic_index,
+      .raw_text = m_owner->lexer.CurrentLine(),
+      .line_number = m_owner->lexer.LineNumber(),
+      .is_extended = extended,
+  };
+  m_operand_scan_begin = m_output_result.operand_pool.size();
+}
+
+void GekkoIRPlugin::AddBinaryEvaluator(u32 (*evaluator)(u32, u32))
+{
+  std::function<u32()> rhs = std::move(m_fixup_stack.top());
+  m_fixup_stack.pop();
+  std::function<u32()> lhs = std::move(m_fixup_stack.top());
+  m_fixup_stack.pop();
+  m_fixup_stack.emplace([evaluator, lhs = std::move(lhs), rhs = std::move(rhs)]() {
+    return evaluator(lhs(), rhs());
+  });
+}
+
+void GekkoIRPlugin::AddUnaryEvaluator(u32 (*evaluator)(u32))
+{
+  std::function<u32()> sub = std::move(m_fixup_stack.top());
+  m_fixup_stack.pop();
+  m_fixup_stack.emplace([evaluator, sub = std::move(sub)]() { return evaluator(sub()); });
+}
+
+void GekkoIRPlugin::AddAbsoluteAddressConv()
+{
+  const u32 inst_address = m_active_block->BlockEndAddress();
+  std::function<u32()> sub = std::move(m_fixup_stack.top());
+  m_fixup_stack.pop();
+  m_fixup_stack.emplace([inst_address, sub = std::move(sub)] { return sub() - inst_address; });
+}
+
+void GekkoIRPlugin::AddLiteral(u32 lit)
+{
+  m_fixup_stack.emplace([lit] { return lit; });
+}
+
+void GekkoIRPlugin::AddSymbolResolve(std::string_view sym, bool absolute)
+{
+  const u32 source_address = m_active_block->BlockEndAddress();
+  AssemblerError err_on_fail = AssemblerError{
+      fmt::format("Unresolved symbol '{}'", sym),
+      m_owner->lexer.CurrentLine(),
+      m_owner->lexer.LineNumber(),
+      // Lexer should currently point to the label, as it hasn't been eaten yet
+      m_owner->lexer.ColNumber(),
+      sym.size(),
+  };
+
+  m_fixup_stack.emplace(
+      [this, sym, absolute, source_address, err_on_fail = std::move(err_on_fail)] {
+        auto label_it = m_labels.find(sym);
+        if (label_it != m_labels.end())
+        {
+          if (absolute)
+          {
+            return label_it->second;
+          }
+          return label_it->second - source_address;
+        }
+
+        auto var_it = m_constants.find(sym);
+        if (var_it != m_constants.end())
+        {
+          return static_cast<u32>(var_it->second);
+        }
+
+        m_owner->error = std::move(err_on_fail);
+        return u32{0};
+      });
+}
+
+void GekkoIRPlugin::SaveOperandFixup(size_t str_left, size_t str_right)
+{
+  m_operand_fixups.emplace_back(std::move(m_fixup_stack.top()));
+  m_fixup_stack.pop();
+  m_output_result.operand_pool.emplace_back(Interval{str_left, str_right - str_left}, 0);
+}
+
+void GekkoIRPlugin::RunFixups()
+{
+  for (size_t i = 0; i < m_operand_fixups.size(); i++)
+  {
+    ValueOf(m_output_result.operand_pool[i]) = m_operand_fixups[i]();
+    if (m_owner->error)
+    {
+      return;
+    }
+  }
+}
+
+void GekkoIRPlugin::FinishInstruction()
+{
+  m_build_inst.op_interval.begin = m_operand_scan_begin;
+  m_build_inst.op_interval.len = m_output_result.operand_pool.size() - m_operand_scan_begin;
+  GetChunk<InstChunk>().emplace_back(m_build_inst);
+  m_operand_scan_begin = 0;
+}
+
+void GekkoIRPlugin::EvalOperatorAbs(AsmOp operation)
+{
+#define EVAL_BINARY_OP(OPERATOR)                                                                   \
+  {                                                                                                \
+    u64 rhs = m_eval_stack.back();                                                                 \
+    m_eval_stack.pop_back();                                                                       \
+    m_eval_stack.back() = m_eval_stack.back() OPERATOR rhs;                                        \
+  }
+
+  switch (operation)
+  {
+  case AsmOp::Or:
+    EVAL_BINARY_OP(|);
+    break;
+  case AsmOp::Xor:
+    EVAL_BINARY_OP(^);
+    break;
+  case AsmOp::And:
+    EVAL_BINARY_OP(&);
+    break;
+  case AsmOp::Lsh:
+    EVAL_BINARY_OP(<<);
+    break;
+  case AsmOp::Rsh:
+    EVAL_BINARY_OP(>>);
+    break;
+  case AsmOp::Add:
+    EVAL_BINARY_OP(+);
+    break;
+  case AsmOp::Sub:
+    EVAL_BINARY_OP(-);
+    break;
+  case AsmOp::Mul:
+    EVAL_BINARY_OP(*);
+    break;
+  case AsmOp::Div:
+    EVAL_BINARY_OP(/);
+    break;
+  case AsmOp::Neg:
+    m_eval_stack.back() = static_cast<u32>(-static_cast<s32>(m_eval_stack.back()));
+    break;
+  case AsmOp::Not:
+    m_eval_stack.back() = ~m_eval_stack.back();
+    break;
+  }
+#undef EVAL_BINARY_OP
+#undef EVAL_UNARY_OP
+}
+
+void GekkoIRPlugin::EvalOperatorRel(AsmOp operation)
+{
+  switch (operation)
+  {
+  case AsmOp::Or:
+    AddBinaryEvaluator([](u32 lhs, u32 rhs) { return lhs | rhs; });
+    break;
+  case AsmOp::Xor:
+    AddBinaryEvaluator([](u32 lhs, u32 rhs) { return lhs ^ rhs; });
+    break;
+  case AsmOp::And:
+    AddBinaryEvaluator([](u32 lhs, u32 rhs) { return lhs & rhs; });
+    break;
+  case AsmOp::Lsh:
+    AddBinaryEvaluator([](u32 lhs, u32 rhs) { return lhs << rhs; });
+    break;
+  case AsmOp::Rsh:
+    AddBinaryEvaluator([](u32 lhs, u32 rhs) { return lhs >> rhs; });
+    break;
+  case AsmOp::Add:
+    AddBinaryEvaluator([](u32 lhs, u32 rhs) { return lhs + rhs; });
+    break;
+  case AsmOp::Sub:
+    AddBinaryEvaluator([](u32 lhs, u32 rhs) { return lhs - rhs; });
+    break;
+  case AsmOp::Mul:
+    AddBinaryEvaluator([](u32 lhs, u32 rhs) { return lhs * rhs; });
+    break;
+  case AsmOp::Div:
+    AddBinaryEvaluator([](u32 lhs, u32 rhs) { return lhs / rhs; });
+    break;
+  case AsmOp::Neg:
+    AddUnaryEvaluator([](u32 val) { return static_cast<u32>(-static_cast<s32>(val)); });
+    break;
+  case AsmOp::Not:
+    AddUnaryEvaluator([](u32 val) { return ~val; });
+    break;
+  }
+}
+
+void GekkoIRPlugin::EvalTerminalRel(Terminal type, const AssemblerToken& tok)
+{
+  switch (type)
+  {
+  case Terminal::Hex:
+  case Terminal::Dec:
+  case Terminal::Oct:
+  case Terminal::Bin:
+  case Terminal::GPR:
+  case Terminal::FPR:
+  case Terminal::SPR:
+  case Terminal::CRField:
+  case Terminal::Lt:
+  case Terminal::Gt:
+  case Terminal::Eq:
+  case Terminal::So:
+  {
+    std::optional<u32> val = tok.EvalToken<u32>();
+    ASSERT(val.has_value());
+    AddLiteral(*val);
+    break;
+  }
+
+  case Terminal::Dot:
+    AddLiteral(CurrentAddress());
+    break;
+
+  case Terminal::Id:
+  {
+    if (auto label_it = m_labels.find(tok.token_val); label_it != m_labels.end())
+    {
+      AddLiteral(label_it->second - CurrentAddress());
+    }
+    else if (auto var_it = m_constants.find(tok.token_val); var_it != m_constants.end())
+    {
+      AddLiteral(var_it->second);
+    }
+    else
+    {
+      AddSymbolResolve(tok.token_val, false);
+    }
+    break;
+  }
+
+  // Parser should disallow this from happening
+  default:
+    ASSERT(false);
+    break;
+  }
+}
+
+void GekkoIRPlugin::EvalTerminalAbs(Terminal type, const AssemblerToken& tok)
+{
+  switch (type)
+  {
+  case Terminal::Hex:
+  case Terminal::Dec:
+  case Terminal::Oct:
+  case Terminal::Bin:
+  case Terminal::GPR:
+  case Terminal::FPR:
+  case Terminal::SPR:
+  case Terminal::CRField:
+  case Terminal::Lt:
+  case Terminal::Gt:
+  case Terminal::Eq:
+  case Terminal::So:
+  {
+    std::optional<u64> val = tok.EvalToken<u64>();
+    ASSERT(val.has_value());
+    m_eval_stack.push_back(*val);
+    break;
+  }
+
+  case Terminal::Flt:
+  {
+    std::visit(
+        [&tok](auto&& vec) {
+          auto opt = tok.EvalToken<typename std::decay_t<decltype(vec)>::value_type>();
+          ASSERT(opt.has_value());
+          vec.push_back(*opt);
+        },
+        m_floats_list);
+    break;
+  }
+
+  case Terminal::Dot:
+    m_eval_stack.push_back(static_cast<u64>(CurrentAddress()));
+    break;
+
+  case Terminal::Id:
+  {
+    if (auto label_it = m_labels.find(tok.token_val); label_it != m_labels.end())
+    {
+      m_eval_stack.push_back(label_it->second);
+    }
+    else if (auto var_it = m_constants.find(tok.token_val); var_it != m_constants.end())
+    {
+      m_eval_stack.push_back(var_it->second);
+    }
+    else
+    {
+      m_owner->EmitErrorHere(
+          fmt::format("Undefined reference to Label/Constant '{}'", tok.ValStr()));
+      return;
+    }
+    break;
+  }
+
+  // Parser should disallow this from happening
+  default:
+    ASSERT(false);
+    break;
+  }
+}
+}  // namespace
+
+u32 IRBlock::BlockEndAddress() const
+{
+  return std::accumulate(chunks.begin(), chunks.end(), block_address,
+                         [](u32 acc, const ChunkVariant& chunk) {
+                           size_t size;
+                           if (std::holds_alternative<InstChunk>(chunk))
+                           {
+                             size = std::get<InstChunk>(chunk).size() * 4;
+                           }
+                           else if (std::holds_alternative<ByteChunk>(chunk))
+                           {
+                             size = std::get<ByteChunk>(chunk).size();
+                           }
+                           else if (std::holds_alternative<PadChunk>(chunk))
+                           {
+                             size = std::get<PadChunk>(chunk);
+                           }
+                           else
+                           {
+                             ASSERT(false);
+                             size = 0;
+                           }
+
+                           return acc + static_cast<u32>(size);
+                         });
+}
+
+FailureOr<GekkoIR> ParseToIR(std::string_view assembly, u32 base_virtual_address)
+{
+  GekkoIR ret;
+  GekkoIRPlugin plugin(ret, base_virtual_address);
+
+  ParseWithPlugin(&plugin, assembly);
+
+  if (plugin.Error())
+  {
+    return FailureOr<GekkoIR>(std::move(*plugin.Error()));
+  }
+
+  return std::move(ret);
+}
+
+}  // namespace Common::GekkoAssembler::detail

Source/Core/Common/Assembler/GekkoIRGen.h

@@ -0,0 +1,50 @@
+// Copyright 2023 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <string_view>
+#include <vector>
+
+#include "Common/Assembler/AssemblerShared.h"
+#include "Common/Assembler/GekkoLexer.h"
+#include "Common/CommonTypes.h"
+
+namespace Common::GekkoAssembler::detail
+{
+struct GekkoInstruction
+{
+  // Combination of a mnemonic index and variant:
+  // (<GekkoMnemonic> << 2) | (<variant bits>)
+  size_t mnemonic_index = 0;
+  // Below refers to GekkoParseResult::operand_pool
+  Interval op_interval = Interval{0, 0};
+  // Literal text of this instruction
+  std::string_view raw_text;
+  size_t line_number = 0;
+  bool is_extended = false;
+};
+
+using InstChunk = std::vector<GekkoInstruction>;
+using ByteChunk = std::vector<u8>;
+using PadChunk = size_t;
+using ChunkVariant = std::variant<InstChunk, ByteChunk, PadChunk>;
+
+struct IRBlock
+{
+  explicit IRBlock(u32 address) : block_address(address) {}
+
+  u32 BlockEndAddress() const;
+
+  std::vector<ChunkVariant> chunks;
+  u32 block_address;
+};
+
+struct GekkoIR
+{
+  std::vector<IRBlock> blocks;
+  std::vector<Tagged<Interval, u32>> operand_pool;
+};
+
+FailureOr<GekkoIR> ParseToIR(std::string_view assembly, u32 base_virtual_address);
+}  // namespace Common::GekkoAssembler::detail

Source/Core/Common/Assembler/GekkoLexer.cpp

@@ -0,0 +1,794 @@
+// Copyright 2023 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "Common/Assembler/GekkoLexer.h"
+
+#include "Common/Assert.h"
+
+#include <iterator>
+#include <numeric>
+
+namespace Common::GekkoAssembler::detail
+{
+namespace
+{
+constexpr bool IsOctal(char c)
+{
+  return c >= '0' && c <= '7';
+}
+
+constexpr bool IsBinary(char c)
+{
+  return c == '0' || c == '1';
+}
+
+template <typename T>
+constexpr T ConvertNib(char c)
+{
+  if (c >= 'a' && c <= 'f')
+  {
+    return static_cast<T>(c - 'a' + 10);
+  }
+  if (c >= 'A' && c <= 'F')
+  {
+    return static_cast<T>(c - 'A' + 10);
+  }
+  return static_cast<T>(c - '0');
+}
+
+constexpr TokenType SingleCharToken(char ch)
+{
+  switch (ch)
+  {
+  case ',':
+    return TokenType::Comma;
+  case '(':
+    return TokenType::Lparen;
+  case ')':
+    return TokenType::Rparen;
+  case '|':
+    return TokenType::Pipe;
+  case '^':
+    return TokenType::Caret;
+  case '&':
+    return TokenType::Ampersand;
+  case '+':
+    return TokenType::Plus;
+  case '-':
+    return TokenType::Minus;
+  case '*':
+    return TokenType::Star;
+  case '/':
+    return TokenType::Slash;
+  case '~':
+    return TokenType::Tilde;
+  case '@':
+    return TokenType::At;
+  case ':':
+    return TokenType::Colon;
+  case '`':
+    return TokenType::Grave;
+  case '.':
+    return TokenType::Dot;
+  case '\0':
+    return TokenType::Eof;
+  case '\n':
+    return TokenType::Eol;
+  default:
+    return TokenType::Invalid;
+  }
+}
+
+// Convert a string literal into its raw-data form
+template <typename Cont>
+void ConvertStringLiteral(std::string_view literal, std::back_insert_iterator<Cont> out_it)
+{
+  for (size_t i = 1; i < literal.size() - 1;)
+  {
+    if (literal[i] == '\\')
+    {
+      ++i;
+      if (IsOctal(literal[i]))
+      {
+        // Octal escape
+        char octal_escape = 0;
+        for (char c = literal[i]; IsOctal(c); c = literal[++i])
+        {
+          octal_escape = (octal_escape << 3) + (c - '0');
+        }
+        out_it = static_cast<u8>(octal_escape);
+      }
+      else if (literal[i] == 'x')
+      {
+        // Hex escape
+        char hex_escape = 0;
+        for (char c = literal[++i]; std::isxdigit(c); c = literal[++i])
+        {
+          hex_escape = (hex_escape << 4) + ConvertNib<char>(c);
+        }
+        out_it = static_cast<u8>(hex_escape);
+      }
+      else
+      {
+        char simple_escape;
+        switch (literal[i])
+        {
+        case '\'':
+          simple_escape = '\x27';
+          break;
+        case '"':
+          simple_escape = '\x22';
+          break;
+        case '?':
+          simple_escape = '\x3f';
+          break;
+        case '\\':
+          simple_escape = '\x5c';
+          break;
+        case 'a':
+          simple_escape = '\x07';
+          break;
+        case 'b':
+          simple_escape = '\x08';
+          break;
+        case 'f':
+          simple_escape = '\x0c';
+          break;
+        case 'n':
+          simple_escape = '\x0a';
+          break;
+        case 'r':
+          simple_escape = '\x0d';
+          break;
+        case 't':
+          simple_escape = '\x09';
+          break;
+        case 'v':
+          simple_escape = '\x0b';
+          break;
+        default:
+          simple_escape = literal[i];
+          break;
+        }
+        out_it = static_cast<u8>(simple_escape);
+        ++i;
+      }
+    }
+    else
+    {
+      out_it = static_cast<u8>(literal[i]);
+      ++i;
+    }
+  }
+}
+
+template <typename T>
+std::optional<T> EvalIntegral(TokenType tp, std::string_view val)
+{
+  constexpr auto hex_step = [](T acc, char c) { return acc << 4 | ConvertNib<T>(c); };
+  constexpr auto dec_step = [](T acc, char c) { return acc * 10 + (c - '0'); };
+  constexpr auto oct_step = [](T acc, char c) { return acc << 3 | (c - '0'); };
+  constexpr auto bin_step = [](T acc, char c) { return acc << 1 | (c - '0'); };
+
+  switch (tp)
+  {
+  case TokenType::HexadecimalLit:
+    return std::accumulate(val.begin() + 2, val.end(), T{0}, hex_step);
+  case TokenType::DecimalLit:
+    return std::accumulate(val.begin(), val.end(), T{0}, dec_step);
+  case TokenType::OctalLit:
+    return std::accumulate(val.begin() + 1, val.end(), T{0}, oct_step);
+  case TokenType::BinaryLit:
+    return std::accumulate(val.begin() + 2, val.end(), T{0}, bin_step);
+  case TokenType::GPR:
+  case TokenType::FPR:
+    return std::accumulate(val.begin() + 1, val.end(), T{0}, dec_step);
+  case TokenType::CRField:
+    return std::accumulate(val.begin() + 2, val.end(), T{0}, dec_step);
+  case TokenType::SPR:
+    return static_cast<T>(*sprg_map.Find(val));
+  case TokenType::Lt:
+    return T{0};
+  case TokenType::Gt:
+    return T{1};
+  case TokenType::Eq:
+    return T{2};
+  case TokenType::So:
+    return T{3};
+  default:
+    return std::nullopt;
+  }
+}
+}  // namespace
+
+void ConvertStringLiteral(std::string_view literal, std::vector<u8>* out_vec)
+{
+  ConvertStringLiteral(literal, std::back_inserter(*out_vec));
+}
+
+std::string_view TokenTypeToStr(TokenType tp)
+{
+  switch (tp)
+  {
+  case TokenType::GPR:
+    return "GPR";
+  case TokenType::FPR:
+    return "FPR";
+  case TokenType::SPR:
+    return "SPR";
+  case TokenType::CRField:
+    return "CR Field";
+  case TokenType::Lt:
+  case TokenType::Gt:
+  case TokenType::Eq:
+  case TokenType::So:
+    return "CR Bit";
+  case TokenType::Identifier:
+    return "Identifier";
+  case TokenType::StringLit:
+    return "String Literal";
+  case TokenType::DecimalLit:
+    return "Decimal Literal";
+  case TokenType::BinaryLit:
+    return "Binary Literal";
+  case TokenType::HexadecimalLit:
+    return "Hexadecimal Literal";
+  case TokenType::OctalLit:
+    return "Octal Literal";
+  case TokenType::FloatLit:
+    return "Float Literal";
+  case TokenType::Invalid:
+    return "Invalid";
+  case TokenType::Lsh:
+    return "<<";
+  case TokenType::Rsh:
+    return ">>";
+  case TokenType::Comma:
+    return ",";
+  case TokenType::Lparen:
+    return "(";
+  case TokenType::Rparen:
+    return ")";
+  case TokenType::Pipe:
+    return "|";
+  case TokenType::Caret:
+    return "^";
+  case TokenType::Ampersand:
+    return "&";
+  case TokenType::Plus:
+    return "+";
+  case TokenType::Minus:
+    return "-";
+  case TokenType::Star:
+    return "*";
+  case TokenType::Slash:
+    return "/";
+  case TokenType::Tilde:
+    return "~";
+  case TokenType::At:
+    return "@";
+  case TokenType::Colon:
+    return ":";
+  case TokenType::Grave:
+    return "`";
+  case TokenType::Dot:
+    return ".";
+  case TokenType::Eof:
+    return "End of File";
+  case TokenType::Eol:
+    return "End of Line";
+  default:
+    return "";
+  }
+}
+
+std::string_view AssemblerToken::TypeStr() const
+{
+  return TokenTypeToStr(token_type);
+}
+
+std::string_view AssemblerToken::ValStr() const
+{
+  switch (token_type)
+  {
+  case TokenType::Eol:
+    return "<EOL>";
+  case TokenType::Eof:
+    return "<EOF>";
+  default:
+    return token_val;
+  }
+}
+
+template <>
+std::optional<float> AssemblerToken::EvalToken() const
+{
+  if (token_type == TokenType::FloatLit)
+  {
+    return std::stof(std::string(token_val));
+  }
+  return std::nullopt;
+}
+
+template <>
+std::optional<double> AssemblerToken::EvalToken() const
+{
+  if (token_type == TokenType::FloatLit)
+  {
+    return std::stod(std::string(token_val));
+  }
+  return std::nullopt;
+}
+
+template <>
+std::optional<u8> AssemblerToken::EvalToken() const
+{
+  return EvalIntegral<u8>(token_type, token_val);
+}
+
+template <>
+std::optional<u16> AssemblerToken::EvalToken() const
+{
+  return EvalIntegral<u16>(token_type, token_val);
+}
+
+template <>
+std::optional<u32> AssemblerToken::EvalToken() const
+{
+  return EvalIntegral<u32>(token_type, token_val);
+}
+
+template <>
+std::optional<u64> AssemblerToken::EvalToken() const
+{
+  return EvalIntegral<u64>(token_type, token_val);
+}
+
+size_t Lexer::LineNumber() const
+{
+  return m_lexed_tokens.empty() ? m_pos.line : TagOf(m_lexed_tokens.front()).line;
+}
+
+size_t Lexer::ColNumber() const
+{
+  return m_lexed_tokens.empty() ? m_pos.col : TagOf(m_lexed_tokens.front()).col;
+}
+
+std::string_view Lexer::CurrentLine() const
+{
+  const size_t line_index =
+      m_lexed_tokens.empty() ? m_pos.index : TagOf(m_lexed_tokens.front()).index;
+  size_t begin_index = line_index == 0 ? 0 : line_index - 1;
+  for (; begin_index > 0; begin_index--)
+  {
+    if (m_lex_string[begin_index] == '\n')
+    {
+      begin_index++;
+      break;
+    }
+  }
+  size_t end_index = begin_index;
+  for (; end_index < m_lex_string.size(); end_index++)
+  {
+    if (m_lex_string[end_index] == '\n')
+    {
+      end_index++;
+      break;
+    }
+  }
+  return m_lex_string.substr(begin_index, end_index - begin_index);
+}
+
+void Lexer::SetIdentifierMatchRule(IdentifierMatchRule set)
+{
+  FeedbackTokens();
+  m_match_rule = set;
+}
+
+const Tagged<CursorPosition, AssemblerToken>& Lexer::LookaheadTagRef(size_t num_fwd) const
+{
+  while (m_lexed_tokens.size() < num_fwd)
+  {
+    LookaheadRef();
+  }
+  return m_lexed_tokens[num_fwd];
+}
+
+AssemblerToken Lexer::Lookahead() const
+{
+  if (m_lexed_tokens.empty())
+  {
+    CursorPosition pos_pre = m_pos;
+    m_lexed_tokens.emplace_back(pos_pre, LexSingle());
+  }
+  return ValueOf(m_lexed_tokens.front());
+}
+
+const AssemblerToken& Lexer::LookaheadRef() const
+{
+  if (m_lexed_tokens.empty())
+  {
+    CursorPosition pos_pre = m_pos;
+    m_lexed_tokens.emplace_back(pos_pre, LexSingle());
+  }
+  return ValueOf(m_lexed_tokens.front());
+}
+
+TokenType Lexer::LookaheadType() const
+{
+  return LookaheadRef().token_type;
+}
+
+AssemblerToken Lexer::LookaheadFloat() const
+{
+  FeedbackTokens();
+  SkipWs();
+
+  CursorPosition pos_pre = m_pos;
+  ScanStart();
+
+  std::optional<std::string_view> failure_reason = RunDfa(float_dfa);
+
+  // Special case: lex at least a single char for no matches for errors to make sense
+  if (m_scan_pos.index == pos_pre.index)
+  {
+    Step();
+  }
+
+  std::string_view tok_str = ScanFinishOut();
+  AssemblerToken tok;
+  if (!failure_reason)
+  {
+    tok = AssemblerToken{
+        TokenType::FloatLit,
+        tok_str,
+        "",
+        Interval{0, 0},
+    };
+  }
+  else
+  {
+    tok = AssemblerToken{
+        TokenType::Invalid,
+        tok_str,
+        *failure_reason,
+        Interval{0, tok_str.length()},
+    };
+  }
+
+  m_lexed_tokens.emplace_back(pos_pre, tok);
+  return tok;
+}
+
+void Lexer::Eat()
+{
+  if (m_lexed_tokens.empty())
+  {
+    LexSingle();
+  }
+  else
+  {
+    m_lexed_tokens.pop_front();
+  }
+}
+
+void Lexer::EatAndReset()
+{
+  Eat();
+  SetIdentifierMatchRule(IdentifierMatchRule::Typical);
+}
+
+std::optional<std::string_view> Lexer::RunDfa(const std::vector<DfaNode>& dfa) const
+{
+  size_t dfa_index = 0;
+  bool transition_found;
+  do
+  {
+    transition_found = false;
+    if (Peek() == '\0')
+    {
+      break;
+    }
+
+    const DfaNode& n = dfa[dfa_index];
+    for (auto&& edge : n.edges)
+    {
+      if (edge.first(Peek()))
+      {
+        transition_found = true;
+        dfa_index = edge.second;
+        break;
+      }
+    }
+
+    if (transition_found)
+    {
+      Step();
+    }
+  } while (transition_found);
+
+  return dfa[dfa_index].match_failure_reason;
+}
+
+void Lexer::SkipWs() const
+{
+  ScanStart();
+  for (char c = Peek(); std::isspace(c) && c != '\n'; c = Step().Peek())
+  {
+  }
+  if (Peek() == '#')
+  {
+    while (Peek() != '\n' && Peek() != '\0')
+    {
+      Step();
+    }
+  }
+  ScanFinish();
+}
+
+void Lexer::FeedbackTokens() const
+{
+  if (m_lexed_tokens.empty())
+  {
+    return;
+  }
+  m_pos = m_scan_pos = TagOf(m_lexed_tokens.front());
+  m_lexed_tokens.clear();
+}
+
+bool Lexer::IdentifierHeadExtra(char h) const
+{
+  switch (m_match_rule)
+  {
+  case IdentifierMatchRule::Typical:
+  case IdentifierMatchRule::Mnemonic:
+    return false;
+  case IdentifierMatchRule::Directive:
+    return std::isdigit(h);
+  }
+  return false;
+}
+
+bool Lexer::IdentifierExtra(char c) const
+{
+  switch (m_match_rule)
+  {
+  case IdentifierMatchRule::Typical:
+  case IdentifierMatchRule::Directive:
+    return false;
+  case IdentifierMatchRule::Mnemonic:
+    return c == '+' || c == '-' || c == '.';
+  }
+  return false;
+}
+
+void Lexer::ScanStart() const
+{
+  m_scan_pos = m_pos;
+}
+
+void Lexer::ScanFinish() const
+{
+  m_pos = m_scan_pos;
+}
+
+std::string_view Lexer::ScanFinishOut() const
+{
+  const size_t start = m_pos.index;
+  m_pos = m_scan_pos;
+  return m_lex_string.substr(start, m_scan_pos.index - start);
+}
+
+char Lexer::Peek() const
+{
+  if (m_scan_pos.index >= m_lex_string.length())
+  {
+    return 0;
+  }
+  return m_lex_string[m_scan_pos.index];
+}
+
+const Lexer& Lexer::Step() const
+{
+  if (m_scan_pos.index >= m_lex_string.length())
+  {
+    return *this;
+  }
+
+  if (Peek() == '\n')
+  {
+    m_scan_pos.line++;
+    m_scan_pos.col = 0;
+  }
+  else
+  {
+    m_scan_pos.col++;
+  }
+  m_scan_pos.index++;
+  return *this;
+}
+
+TokenType Lexer::LexStringLit(std::string_view& invalid_reason, Interval& invalid_region) const
+{
+  // The open quote has alread been matched
+  const size_t string_start = m_scan_pos.index - 1;
+  TokenType token_type = TokenType::StringLit;
+
+  std::optional<std::string_view> failure_reason = RunDfa(string_dfa);
+
+  if (failure_reason)
+  {
+    token_type = TokenType::Invalid;
+    invalid_reason = *failure_reason;
+    invalid_region = Interval{0, m_scan_pos.index - string_start};
+  }
+
+  return token_type;
+}
+
+TokenType Lexer::ClassifyAlnum() const
+{
+  const std::string_view alnum = m_lex_string.substr(m_pos.index, m_scan_pos.index - m_pos.index);
+  constexpr auto valid_regnum = [](std::string_view rn) {
+    if (rn.length() == 1 && std::isdigit(rn[0]))
+    {
+      return true;
+    }
+    else if (rn.length() == 2 && std::isdigit(rn[0]) && std::isdigit(rn[1]))
+    {
+      if (rn[0] == '1' || rn[0] == '2')
+      {
+        return true;
+      }
+
+      if (rn[0] == '3')
+      {
+        return rn[1] <= '2';
+      }
+    }
+
+    return false;
+  };
+  constexpr auto eq_nocase = [](std::string_view str, std::string_view lwr) {
+    auto it_l = str.cbegin(), it_r = lwr.cbegin();
+    for (; it_l != str.cend() && it_r != lwr.cend(); it_l++, it_r++)
+    {
+      if (std::tolower(*it_l) != *it_r)
+      {
+        return false;
+      }
+    }
+    return it_l == str.end() && it_r == lwr.end();
+  };
+
+  if (std::tolower(alnum[0]) == 'r' && valid_regnum(alnum.substr(1)))
+  {
+    return TokenType::GPR;
+  }
+  else if (std::tolower(alnum[0]) == 'f' && valid_regnum(alnum.substr(1)))
+  {
+    return TokenType::FPR;
+  }
+  else if (alnum.length() == 3 && eq_nocase(alnum.substr(0, 2), "cr") && alnum[2] >= '0' &&
+           alnum[2] <= '7')
+  {
+    return TokenType::CRField;
+  }
+  else if (eq_nocase(alnum, "lt"))
+  {
+    return TokenType::Lt;
+  }
+  else if (eq_nocase(alnum, "gt"))
+  {
+    return TokenType::Gt;
+  }
+  else if (eq_nocase(alnum, "eq"))
+  {
+    return TokenType::Eq;
+  }
+  else if (eq_nocase(alnum, "so"))
+  {
+    return TokenType::So;
+  }
+  else if (sprg_map.Find(alnum) != nullptr)
+  {
+    return TokenType::SPR;
+  }
+  return TokenType::Identifier;
+}
+
+AssemblerToken Lexer::LexSingle() const
+{
+  SkipWs();
+
+  ScanStart();
+  const char h = Peek();
+
+  TokenType token_type;
+  std::string_view invalid_reason = "";
+  Interval invalid_region = Interval{0, 0};
+
+  Step();
+
+  if (std::isalpha(h) || h == '_' || IdentifierHeadExtra(h))
+  {
+    for (char c = Peek(); std::isalnum(c) || c == '_' || IdentifierExtra(c); c = Step().Peek())
+    {
+    }
+
+    token_type = ClassifyAlnum();
+  }
+  else if (h == '"')
+  {
+    token_type = LexStringLit(invalid_reason, invalid_region);
+  }
+  else if (h == '0')
+  {
+    const char imm_type = Peek();
+
+    if (imm_type == 'x')
+    {
+      token_type = TokenType::HexadecimalLit;
+      Step();
+      for (char c = Peek(); std::isxdigit(c); c = Step().Peek())
+      {
+      }
+    }
+    else if (imm_type == 'b')
+    {
+      token_type = TokenType::BinaryLit;
+      Step();
+      for (char c = Peek(); IsBinary(c); c = Step().Peek())
+      {
+      }
+    }
+    else if (IsOctal(imm_type))
+    {
+      token_type = TokenType::OctalLit;
+      for (char c = Peek(); IsOctal(c); c = Step().Peek())
+      {
+      }
+    }
+    else
+    {
+      token_type = TokenType::DecimalLit;
+    }
+  }
+  else if (std::isdigit(h))
+  {
+    for (char c = Peek(); std::isdigit(c); c = Step().Peek())
+    {
+    }
+    token_type = TokenType::DecimalLit;
+  }
+  else if (h == '<' || h == '>')
+  {
+    // Special case for two-character operators
+    const char second_ch = Peek();
+    if (second_ch == h)
+    {
+      Step();
+      token_type = second_ch == '<' ? TokenType::Lsh : TokenType::Rsh;
+    }
+    else
+    {
+      token_type = TokenType::Invalid;
+      invalid_reason = "Unrecognized character";
+      invalid_region = Interval{0, 1};
+    }
+  }
+  else
+  {
+    token_type = SingleCharToken(h);
+    if (token_type == TokenType::Invalid)
+    {
+      invalid_reason = "Unrecognized character";
+      invalid_region = Interval{0, 1};
+    }
+  }
+
+  AssemblerToken new_tok = {token_type, ScanFinishOut(), invalid_reason, invalid_region};
+  SkipWs();
+  return new_tok;
+}
+}  // namespace Common::GekkoAssembler::detail

Source/Core/Common/Assembler/GekkoLexer.h

@@ -0,0 +1,188 @@
+// Copyright 2023 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <algorithm>
+#include <array>
+#include <deque>
+#include <optional>
+#include <string_view>
+#include <type_traits>
+#include <vector>
+
+#include "Common/Assembler/AssemblerShared.h"
+#include "Common/Assembler/AssemblerTables.h"
+#include "Common/CommonTypes.h"
+
+namespace Common::GekkoAssembler::detail
+{
+void ConvertStringLiteral(std::string_view literal, std::vector<u8>* out_vec);
+
+enum class TokenType
+{
+  Invalid,
+  Identifier,
+  StringLit,
+  HexadecimalLit,
+  DecimalLit,
+  OctalLit,
+  BinaryLit,
+  FloatLit,
+  GPR,
+  FPR,
+  CRField,
+  SPR,
+  Lt,
+  Gt,
+  Eq,
+  So,
+  // EOL signifies boundaries between instructions, a la ';'
+  Eol,
+  Eof,
+
+  Dot,
+  Colon,
+  Comma,
+  Lparen,
+  Rparen,
+  Pipe,
+  Caret,
+  Ampersand,
+  Lsh,
+  Rsh,
+  Plus,
+  Minus,
+  Star,
+  Slash,
+  Tilde,
+  Grave,
+  At,
+
+  OperatorBegin = Dot,
+  LastToken = At,
+};
+
+std::string_view TokenTypeToStr(TokenType);
+
+struct AssemblerToken
+{
+  TokenType token_type;
+  std::string_view token_val;
+  std::string_view invalid_reason;
+  // Within an invalid token, specifies the erroneous region
+  Interval invalid_region;
+
+  std::string_view TypeStr() const;
+  std::string_view ValStr() const;
+
+  // Supported Templates:
+  // u8, u16, u32, u64, float, double
+  template <typename T>
+  std::optional<T> EvalToken() const;
+};
+
+struct CursorPosition
+{
+  size_t index = 0;
+  size_t line = 0;
+  size_t col = 0;
+};
+
+class Lexer
+{
+public:
+  enum class IdentifierMatchRule
+  {
+    Typical,
+    Mnemonic,   // Mnemonics can contain +, -, or . to specify branch prediction rules and link bit
+    Directive,  // Directives can start with a digit
+  };
+
+public:
+  explicit Lexer(std::string_view str)
+      : m_lex_string(str), m_match_rule(IdentifierMatchRule::Typical)
+  {
+  }
+
+  size_t LineNumber() const;
+  size_t ColNumber() const;
+  std::string_view CurrentLine() const;
+
+  // Since there's only one place floats get lexed, it's 'okay' to have an explicit
+  // "lex a float token" function
+  void SetIdentifierMatchRule(IdentifierMatchRule set);
+  const Tagged<CursorPosition, AssemblerToken>& LookaheadTagRef(size_t num_fwd) const;
+  AssemblerToken Lookahead() const;
+  const AssemblerToken& LookaheadRef() const;
+  TokenType LookaheadType() const;
+  // Since there's only one place floats get lexed, it's 'okay' to have an explicit
+  // "lex a float token" function
+  AssemblerToken LookaheadFloat() const;
+  void Eat();
+  void EatAndReset();
+
+  template <size_t N>
+  void LookaheadTaggedN(std::array<Tagged<CursorPosition, AssemblerToken>, N>* tokens_out) const
+  {
+    const size_t filled_amt = std::min(m_lexed_tokens.size(), N);
+
+    std::copy_n(m_lexed_tokens.begin(), filled_amt, tokens_out->begin());
+
+    std::generate_n(tokens_out->begin() + filled_amt, N - filled_amt, [this] {
+      CursorPosition p = m_pos;
+      return m_lexed_tokens.emplace_back(p, LexSingle());
+    });
+  }
+
+  template <size_t N>
+  void LookaheadN(std::array<AssemblerToken, N>* tokens_out) const
+  {
+    const size_t filled_amt = std::min(m_lexed_tokens.size(), N);
+
+    auto _it = m_lexed_tokens.begin();
+    std::generate_n(tokens_out->begin(), filled_amt, [&_it] { return ValueOf(*_it++); });
+
+    std::generate_n(tokens_out->begin() + filled_amt, N - filled_amt, [this] {
+      CursorPosition p = m_pos;
+      return ValueOf(m_lexed_tokens.emplace_back(p, LexSingle()));
+    });
+  }
+
+  template <size_t N>
+  void EatN()
+  {
+    size_t consumed = 0;
+    while (m_lexed_tokens.size() > 0 && consumed < N)
+    {
+      m_lexed_tokens.pop_front();
+      consumed++;
+    }
+    for (size_t i = consumed; i < N; i++)
+    {
+      LexSingle();
+    }
+  }
+
+private:
+  std::optional<std::string_view> RunDfa(const std::vector<DfaNode>& dfa) const;
+  void SkipWs() const;
+  void FeedbackTokens() const;
+  bool IdentifierHeadExtra(char h) const;
+  bool IdentifierExtra(char c) const;
+  void ScanStart() const;
+  void ScanFinish() const;
+  std::string_view ScanFinishOut() const;
+  char Peek() const;
+  const Lexer& Step() const;
+  TokenType LexStringLit(std::string_view& invalid_reason, Interval& invalid_region) const;
+  TokenType ClassifyAlnum() const;
+  AssemblerToken LexSingle() const;
+
+  std::string_view m_lex_string;
+  mutable CursorPosition m_pos;
+  mutable CursorPosition m_scan_pos;
+  mutable std::deque<Tagged<CursorPosition, AssemblerToken>> m_lexed_tokens;
+  IdentifierMatchRule m_match_rule;
+};
+}  // namespace Common::GekkoAssembler::detail

Source/Core/Common/Assembler/GekkoParser.cpp

@@ -0,0 +1,885 @@
+// Copyright 2023 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "Common/Assembler/GekkoParser.h"
+
+#include <algorithm>
+#include <array>
+#include <functional>
+
+#include <fmt/format.h>
+
+#include "Common/Assembler/AssemblerShared.h"
+#include "Common/Assembler/AssemblerTables.h"
+#include "Common/Assembler/GekkoLexer.h"
+#include "Common/Assert.h"
+
+namespace Common::GekkoAssembler::detail
+{
+namespace
+{
+bool MatchOperandFirst(const AssemblerToken& tok)
+{
+  switch (tok.token_type)
+  {
+  case TokenType::Minus:
+  case TokenType::Tilde:
+  case TokenType::Lparen:
+  case TokenType::Grave:
+  case TokenType::Identifier:
+  case TokenType::DecimalLit:
+  case TokenType::OctalLit:
+  case TokenType::HexadecimalLit:
+  case TokenType::BinaryLit:
+  case TokenType::Dot:
+    return true;
+  default:
+    return false;
+  }
+}
+
+void ParseImm(ParseState* state)
+{
+  AssemblerToken tok = state->lexer.Lookahead();
+  switch (tok.token_type)
+  {
+  case TokenType::HexadecimalLit:
+    state->plugin.OnTerminal(Terminal::Hex, tok);
+    break;
+  case TokenType::DecimalLit:
+    state->plugin.OnTerminal(Terminal::Dec, tok);
+    break;
+  case TokenType::OctalLit:
+    state->plugin.OnTerminal(Terminal::Oct, tok);
+    break;
+  case TokenType::BinaryLit:
+    state->plugin.OnTerminal(Terminal::Bin, tok);
+    break;
+  default:
+    state->EmitErrorHere(fmt::format("Invalid {} with value '{}'", tok.TypeStr(), tok.ValStr()));
+    return;
+  }
+  if (state->error)
+  {
+    return;
+  }
+  state->lexer.Eat();
+}
+
+void ParseId(ParseState* state)
+{
+  AssemblerToken tok = state->lexer.Lookahead();
+  if (tok.token_type == TokenType::Identifier)
+  {
+    state->plugin.OnTerminal(Terminal::Id, tok);
+    if (state->error)
+    {
+      return;
+    }
+    state->lexer.Eat();
+  }
+  else
+  {
+    state->EmitErrorHere(fmt::format("Expected an identifier, but found '{}'", tok.ValStr()));
+  }
+}
+
+void ParseIdLocation(ParseState* state)
+{
+  std::array<AssemblerToken, 3> toks;
+  state->lexer.LookaheadN(&toks);
+
+  if (toks[1].token_type == TokenType::At)
+  {
+    if (toks[2].token_val == "ha")
+    {
+      state->plugin.OnHiaddr(toks[0].token_val);
+      if (state->error)
+      {
+        return;
+      }
+      state->lexer.EatN<3>();
+      return;
+    }
+    else if (toks[2].token_val == "l")
+    {
+      state->plugin.OnLoaddr(toks[0].token_val);
+      if (state->error)
+      {
+        return;
+      }
+      state->lexer.EatN<3>();
+      return;
+    }
+  }
+
+  ParseId(state);
+}
+
+void ParsePpcBuiltin(ParseState* state)
+{
+  AssemblerToken tok = state->lexer.Lookahead();
+  switch (tok.token_type)
+  {
+  case TokenType::GPR:
+    state->plugin.OnTerminal(Terminal::GPR, tok);
+    break;
+  case TokenType::FPR:
+    state->plugin.OnTerminal(Terminal::FPR, tok);
+    break;
+  case TokenType::SPR:
+    state->plugin.OnTerminal(Terminal::SPR, tok);
+    break;
+  case TokenType::CRField:
+    state->plugin.OnTerminal(Terminal::CRField, tok);
+    break;
+  case TokenType::Lt:
+    state->plugin.OnTerminal(Terminal::Lt, tok);
+    break;
+  case TokenType::Gt:
+    state->plugin.OnTerminal(Terminal::Gt, tok);
+    break;
+  case TokenType::Eq:
+    state->plugin.OnTerminal(Terminal::Eq, tok);
+    break;
+  case TokenType::So:
+    state->plugin.OnTerminal(Terminal::So, tok);
+    break;
+  default:
+    state->EmitErrorHere(
+        fmt::format("Unexpected token '{}' in ppc builtin", state->lexer.LookaheadRef().ValStr()));
+    break;
+  }
+  if (state->error)
+  {
+    return;
+  }
+  state->lexer.Eat();
+}
+
+void ParseBaseexpr(ParseState* state)
+{
+  TokenType tok = state->lexer.LookaheadType();
+  switch (tok)
+  {
+  case TokenType::HexadecimalLit:
+  case TokenType::DecimalLit:
+  case TokenType::OctalLit:
+  case TokenType::BinaryLit:
+    ParseImm(state);
+    break;
+
+  case TokenType::Identifier:
+    ParseIdLocation(state);
+    break;
+
+  case TokenType::GPR:
+  case TokenType::FPR:
+  case TokenType::SPR:
+  case TokenType::CRField:
+  case TokenType::Lt:
+  case TokenType::Gt:
+  case TokenType::Eq:
+  case TokenType::So:
+    ParsePpcBuiltin(state);
+    break;
+
+  case TokenType::Dot:
+    state->plugin.OnTerminal(Terminal::Dot, state->lexer.Lookahead());
+    if (state->error)
+    {
+      return;
+    }
+    state->lexer.Eat();
+    break;
+
+  default:
+    state->EmitErrorHere(
+        fmt::format("Unexpected token '{}' in expression", state->lexer.LookaheadRef().ValStr()));
+    break;
+  }
+}
+
+void ParseBitor(ParseState* state);
+void ParseParen(ParseState* state)
+{
+  if (state->HasToken(TokenType::Lparen))
+  {
+    state->plugin.OnOpenParen(ParenType::Normal);
+    if (state->error)
+    {
+      return;
+    }
+
+    state->lexer.Eat();
+    ParseBitor(state);
+    if (state->error)
+    {
+      return;
+    }
+
+    if (state->HasToken(TokenType::Rparen))
+    {
+      state->plugin.OnCloseParen(ParenType::Normal);
+    }
+    state->ParseToken(TokenType::Rparen);
+  }
+  else if (state->HasToken(TokenType::Grave))
+  {
+    state->plugin.OnOpenParen(ParenType::RelConv);
+
+    state->lexer.Eat();
+    ParseBitor(state);
+    if (state->error)
+    {
+      return;
+    }
+
+    if (state->HasToken(TokenType::Grave))
+    {
+      state->plugin.OnCloseParen(ParenType::RelConv);
+    }
+    state->ParseToken(TokenType::Grave);
+  }
+  else
+  {
+    ParseBaseexpr(state);
+  }
+}
+
+void ParseUnary(ParseState* state)
+{
+  TokenType tok = state->lexer.LookaheadType();
+  if (tok == TokenType::Minus || tok == TokenType::Tilde)
+  {
+    state->lexer.Eat();
+    ParseUnary(state);
+    if (state->error)
+    {
+      return;
+    }
+
+    if (tok == TokenType::Minus)
+    {
+      state->plugin.OnOperator(AsmOp::Neg);
+    }
+    else
+    {
+      state->plugin.OnOperator(AsmOp::Not);
+    }
+  }
+  else
+  {
+    ParseParen(state);
+  }
+}
+
+void ParseMultiplication(ParseState* state)
+{
+  ParseUnary(state);
+  if (state->error)
+  {
+    return;
+  }
+
+  TokenType tok = state->lexer.LookaheadType();
+  while (tok == TokenType::Star || tok == TokenType::Slash)
+  {
+    state->lexer.Eat();
+    ParseUnary(state);
+    if (state->error)
+    {
+      return;
+    }
+
+    if (tok == TokenType::Star)
+    {
+      state->plugin.OnOperator(AsmOp::Mul);
+    }
+    else
+    {
+      state->plugin.OnOperator(AsmOp::Div);
+    }
+    tok = state->lexer.LookaheadType();
+  }
+}
+
+void ParseAddition(ParseState* state)
+{
+  ParseMultiplication(state);
+  if (state->error)
+  {
+    return;
+  }
+
+  TokenType tok = state->lexer.LookaheadType();
+  while (tok == TokenType::Plus || tok == TokenType::Minus)
+  {
+    state->lexer.Eat();
+    ParseMultiplication(state);
+    if (state->error)
+    {
+      return;
+    }
+
+    if (tok == TokenType::Plus)
+    {
+      state->plugin.OnOperator(AsmOp::Add);
+    }
+    else
+    {
+      state->plugin.OnOperator(AsmOp::Sub);
+    }
+    tok = state->lexer.LookaheadType();
+  }
+}
+
+void ParseShift(ParseState* state)
+{
+  ParseAddition(state);
+  if (state->error)
+  {
+    return;
+  }
+
+  TokenType tok = state->lexer.LookaheadType();
+  while (tok == TokenType::Lsh || tok == TokenType::Rsh)
+  {
+    state->lexer.Eat();
+    ParseAddition(state);
+    if (state->error)
+    {
+      return;
+    }
+
+    if (tok == TokenType::Lsh)
+    {
+      state->plugin.OnOperator(AsmOp::Lsh);
+    }
+    else
+    {
+      state->plugin.OnOperator(AsmOp::Rsh);
+    }
+    tok = state->lexer.LookaheadType();
+  }
+}
+
+void ParseBitand(ParseState* state)
+{
+  ParseShift(state);
+  if (state->error)
+  {
+    return;
+  }
+
+  while (state->HasToken(TokenType::Ampersand))
+  {
+    state->lexer.Eat();
+    ParseShift(state);
+    if (state->error)
+    {
+      return;
+    }
+
+    state->plugin.OnOperator(AsmOp::And);
+  }
+}
+
+void ParseBitxor(ParseState* state)
+{
+  ParseBitand(state);
+  if (state->error)
+  {
+    return;
+  }
+
+  while (state->HasToken(TokenType::Caret))
+  {
+    state->lexer.Eat();
+    ParseBitand(state);
+    if (state->error)
+    {
+      return;
+    }
+
+    state->plugin.OnOperator(AsmOp::Xor);
+  }
+}
+
+void ParseBitor(ParseState* state)
+{
+  ParseBitxor(state);
+  if (state->error)
+  {
+    return;
+  }
+
+  while (state->HasToken(TokenType::Pipe))
+  {
+    state->lexer.Eat();
+    ParseBitxor(state);
+    if (state->error)
+    {
+      return;
+    }
+
+    state->plugin.OnOperator(AsmOp::Or);
+  }
+}
+
+void ParseOperand(ParseState* state)
+{
+  state->plugin.OnOperandPre();
+  ParseBitor(state);
+  if (state->error)
+  {
+    return;
+  }
+  state->plugin.OnOperandPost();
+}
+
+void ParseOperandList(ParseState* state, ParseAlg alg)
+{
+  if (alg == ParseAlg::None)
+  {
+    return;
+  }
+  if (alg == ParseAlg::NoneOrOp1)
+  {
+    if (MatchOperandFirst(state->lexer.Lookahead()))
+    {
+      ParseOperand(state);
+    }
+    return;
+  }
+
+  enum ParseStep
+  {
+    _Operand,
+    _Comma,
+    _Lparen,
+    _Rparen,
+    _OptComma
+  };
+  std::vector<ParseStep> steps;
+
+  switch (alg)
+  {
+  case ParseAlg::Op1:
+    steps = {_Operand};
+    break;
+  case ParseAlg::Op1Or2:
+    steps = {_Operand, _OptComma, _Operand};
+    break;
+  case ParseAlg::Op2Or3:
+    steps = {_Operand, _Comma, _Operand, _OptComma, _Operand};
+    break;
+  case ParseAlg::Op1Off1:
+    steps = {_Operand, _Comma, _Operand, _Lparen, _Operand, _Rparen};
+    break;
+  case ParseAlg::Op2:
+    steps = {_Operand, _Comma, _Operand};
+    break;
+  case ParseAlg::Op3:
+    steps = {_Operand, _Comma, _Operand, _Comma, _Operand};
+    break;
+  case ParseAlg::Op4:
+    steps = {_Operand, _Comma, _Operand, _Comma, _Operand, _Comma, _Operand};
+    break;
+  case ParseAlg::Op5:
+    steps = {_Operand, _Comma, _Operand, _Comma, _Operand, _Comma, _Operand, _Comma, _Operand};
+    break;
+  case ParseAlg::Op1Off1Op2:
+    steps = {_Operand, _Comma, _Operand, _Lparen, _Operand,
+             _Rparen,  _Comma, _Operand, _Comma,  _Operand};
+    break;
+  default:
+    ASSERT(false);
+    return;
+  }
+
+  for (ParseStep step : steps)
+  {
+    bool stop_parse = false;
+    switch (step)
+    {
+    case _Operand:
+      ParseOperand(state);
+      break;
+    case _Comma:
+      state->ParseToken(TokenType::Comma);
+      break;
+    case _Lparen:
+      state->ParseToken(TokenType::Lparen);
+      break;
+    case _Rparen:
+      state->ParseToken(TokenType::Rparen);
+      break;
+    case _OptComma:
+      if (state->HasToken(TokenType::Comma))
+      {
+        state->ParseToken(TokenType::Comma);
+      }
+      else
+      {
+        stop_parse = true;
+      }
+      break;
+    }
+    if (state->error)
+    {
+      return;
+    }
+    if (stop_parse)
+    {
+      break;
+    }
+  }
+}
+
+void ParseInstruction(ParseState* state)
+{
+  state->lexer.SetIdentifierMatchRule(Lexer::IdentifierMatchRule::Mnemonic);
+
+  AssemblerToken mnemonic_token = state->lexer.Lookahead();
+  if (mnemonic_token.token_type != TokenType::Identifier)
+  {
+    state->lexer.SetIdentifierMatchRule(Lexer::IdentifierMatchRule::Typical);
+    return;
+  }
+
+  ParseInfo const* parse_info = mnemonic_tokens.Find(mnemonic_token.token_val);
+  bool is_extended = false;
+  if (parse_info == nullptr)
+  {
+    parse_info = extended_mnemonic_tokens.Find(mnemonic_token.token_val);
+    if (parse_info == nullptr)
+    {
+      state->EmitErrorHere(
+          fmt::format("Unknown or unsupported mnemonic '{}'", mnemonic_token.ValStr()));
+      return;
+    }
+    is_extended = true;
+  }
+
+  state->plugin.OnInstructionPre(*parse_info, is_extended);
+
+  state->lexer.EatAndReset();
+
+  ParseOperandList(state, parse_info->parse_algorithm);
+  if (state->error)
+  {
+    return;
+  }
+
+  state->plugin.OnInstructionPost(*parse_info, is_extended);
+}
+
+void ParseLabel(ParseState* state)
+{
+  std::array<AssemblerToken, 2> tokens;
+  state->lexer.LookaheadN(&tokens);
+
+  if (tokens[0].token_type == TokenType::Identifier && tokens[1].token_type == TokenType::Colon)
+  {
+    state->plugin.OnLabelDecl(tokens[0].token_val);
+    if (state->error)
+    {
+      return;
+    }
+    state->lexer.EatN<2>();
+  }
+}
+
+void ParseResolvedExpr(ParseState* state)
+{
+  state->plugin.OnResolvedExprPre();
+  ParseBitor(state);
+  if (state->error)
+  {
+    return;
+  }
+  state->plugin.OnResolvedExprPost();
+}
+
+void ParseExpressionList(ParseState* state)
+{
+  ParseResolvedExpr(state);
+  if (state->error)
+  {
+    return;
+  }
+
+  while (state->HasToken(TokenType::Comma))
+  {
+    state->lexer.Eat();
+    ParseResolvedExpr(state);
+    if (state->error)
+    {
+      return;
+    }
+  }
+}
+
+void ParseFloat(ParseState* state)
+{
+  AssemblerToken flt_token = state->lexer.LookaheadFloat();
+  if (flt_token.token_type != TokenType::FloatLit)
+  {
+    state->EmitErrorHere("Invalid floating point literal");
+    return;
+  }
+  state->plugin.OnTerminal(Terminal::Flt, flt_token);
+  state->lexer.Eat();
+}
+
+void ParseFloatList(ParseState* state)
+{
+  ParseFloat(state);
+  if (state->error)
+  {
+    return;
+  }
+
+  while (state->HasToken(TokenType::Comma))
+  {
+    state->lexer.Eat();
+    ParseFloat(state);
+    if (state->error)
+    {
+      return;
+    }
+  }
+}
+
+void ParseDefvar(ParseState* state)
+{
+  AssemblerToken tok = state->lexer.Lookahead();
+  if (tok.token_type == TokenType::Identifier)
+  {
+    state->plugin.OnVarDecl(tok.token_val);
+    if (state->error)
+    {
+      return;
+    }
+    state->lexer.Eat();
+
+    state->ParseToken(TokenType::Comma);
+    if (state->error)
+    {
+      return;
+    }
+
+    ParseResolvedExpr(state);
+  }
+  else
+  {
+    state->EmitErrorHere(fmt::format("Expected an identifier, but found '{}'", tok.ValStr()));
+  }
+}
+
+void ParseString(ParseState* state)
+{
+  AssemblerToken tok = state->lexer.Lookahead();
+  if (tok.token_type == TokenType::StringLit)
+  {
+    state->plugin.OnTerminal(Terminal::Str, tok);
+    state->lexer.Eat();
+  }
+  else
+  {
+    state->EmitErrorHere(fmt::format("Expected a string literal, but found '{}'", tok.ValStr()));
+  }
+}
+
+void ParseDirective(ParseState* state)
+{
+  // TODO: test directives
+  state->lexer.SetIdentifierMatchRule(Lexer::IdentifierMatchRule::Directive);
+  AssemblerToken tok = state->lexer.Lookahead();
+  if (tok.token_type != TokenType::Identifier)
+  {
+    state->EmitErrorHere(fmt::format("Unexpected token '{}' in directive type", tok.ValStr()));
+    return;
+  }
+
+  GekkoDirective const* directive_enum = directives_map.Find(tok.token_val);
+  if (directive_enum == nullptr)
+  {
+    state->EmitErrorHere(fmt::format("Unknown assembler directive '{}'", tok.ValStr()));
+    return;
+  }
+
+  state->plugin.OnDirectivePre(*directive_enum);
+
+  state->lexer.EatAndReset();
+  switch (*directive_enum)
+  {
+  case GekkoDirective::Byte:
+  case GekkoDirective::_2byte:
+  case GekkoDirective::_4byte:
+  case GekkoDirective::_8byte:
+    ParseExpressionList(state);
+    break;
+
+  case GekkoDirective::Float:
+  case GekkoDirective::Double:
+    ParseFloatList(state);
+    break;
+
+  case GekkoDirective::Locate:
+  case GekkoDirective::Zeros:
+  case GekkoDirective::Skip:
+    ParseResolvedExpr(state);
+    break;
+
+  case GekkoDirective::PadAlign:
+  case GekkoDirective::Align:
+    ParseImm(state);
+    break;
+
+  case GekkoDirective::DefVar:
+    ParseDefvar(state);
+    break;
+
+  case GekkoDirective::Ascii:
+  case GekkoDirective::Asciz:
+    ParseString(state);
+    break;
+  }
+
+  if (state->error)
+  {
+    return;
+  }
+
+  state->plugin.OnDirectivePost(*directive_enum);
+}
+
+void ParseLine(ParseState* state)
+{
+  if (state->HasToken(TokenType::Dot))
+  {
+    state->ParseToken(TokenType::Dot);
+    ParseDirective(state);
+  }
+  else
+  {
+    ParseInstruction(state);
+  }
+}
+
+void ParseProgram(ParseState* state)
+{
+  AssemblerToken tok = state->lexer.Lookahead();
+  if (tok.token_type == TokenType::Eof)
+  {
+    state->eof = true;
+    return;
+  }
+  ParseLabel(state);
+  if (state->error)
+  {
+    return;
+  }
+  ParseLine(state);
+  if (state->error)
+  {
+    return;
+  }
+
+  while (!state->eof && !state->error)
+  {
+    tok = state->lexer.Lookahead();
+    if (tok.token_type == TokenType::Eof)
+    {
+      state->eof = true;
+    }
+    else if (tok.token_type == TokenType::Eol)
+    {
+      state->lexer.Eat();
+      ParseLabel(state);
+      if (state->error)
+      {
+        return;
+      }
+      ParseLine(state);
+    }
+    else
+    {
+      state->EmitErrorHere(
+          fmt::format("Unexpected token '{}' where line should have ended", tok.ValStr()));
+    }
+  }
+}
+}  // namespace
+
+ParseState::ParseState(std::string_view input_str, ParsePlugin& p)
+    : lexer(input_str), plugin(p), eof(false)
+{
+}
+
+bool ParseState::HasToken(TokenType tp) const
+{
+  return lexer.LookaheadType() == tp;
+}
+
+void ParseState::ParseToken(TokenType tp)
+{
+  AssemblerToken tok = lexer.LookaheadRef();
+  if (tok.token_type == tp)
+  {
+    lexer.Eat();
+  }
+  else
+  {
+    EmitErrorHere(fmt::format("Expected '{}' but found '{}'", TokenTypeToStr(tp), tok.ValStr()));
+  }
+}
+
+void ParseState::EmitErrorHere(std::string&& message)
+{
+  AssemblerToken cur_token = lexer.Lookahead();
+  if (cur_token.token_type == TokenType::Invalid)
+  {
+    error = AssemblerError{
+        std::string(cur_token.invalid_reason),
+        lexer.CurrentLine(),
+        lexer.LineNumber(),
+        lexer.ColNumber() + cur_token.invalid_region.begin,
+        cur_token.invalid_region.len,
+    };
+  }
+  else
+  {
+    error = AssemblerError{
+        std::move(message), lexer.CurrentLine(),        lexer.LineNumber(),
+        lexer.ColNumber(),  cur_token.token_val.size(),
+    };
+  }
+}
+
+void ParseWithPlugin(ParsePlugin* plugin, std::string_view input)
+{
+  ParseState parse_state = ParseState(input, *plugin);
+  plugin->SetOwner(&parse_state);
+  ParseProgram(&parse_state);
+
+  if (parse_state.error)
+  {
+    plugin->OnError();
+    plugin->ForwardError(std::move(*parse_state.error));
+  }
+  else
+  {
+    plugin->PostParseAction();
+    if (parse_state.error)
+    {
+      plugin->OnError();
+      plugin->ForwardError(std::move(*parse_state.error));
+    }
+  }
+
+  plugin->SetOwner(nullptr);
+}
+}  // namespace Common::GekkoAssembler::detail

Source/Core/Common/Assembler/GekkoParser.h

@@ -0,0 +1,124 @@
+// Copyright 2023 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <optional>
+#include <string>
+#include <string_view>
+
+#include "Common/Assembler/AssemblerShared.h"
+#include "Common/Assembler/GekkoLexer.h"
+#include "Common/CommonTypes.h"
+
+namespace Common::GekkoAssembler::detail
+{
+class ParsePlugin;
+
+struct ParseState
+{
+  ParseState(std::string_view input_str, ParsePlugin& plugin);
+
+  bool HasToken(TokenType tp) const;
+  void ParseToken(TokenType tp);
+  void EmitErrorHere(std::string&& message);
+
+  Lexer lexer;
+  ParsePlugin& plugin;
+
+  std::optional<AssemblerError> error;
+  bool eof;
+};
+
+enum class AsmOp
+{
+  Or,
+  Xor,
+  And,
+  Lsh,
+  Rsh,
+  Add,
+  Sub,
+  Mul,
+  Div,
+  Neg,
+  Not
+};
+
+enum class Terminal
+{
+  Hex,
+  Dec,
+  Oct,
+  Bin,
+  Flt,
+  Str,
+  Id,
+  GPR,
+  FPR,
+  SPR,
+  CRField,
+  Lt,
+  Gt,
+  Eq,
+  So,
+  Dot,
+};
+
+enum class ParenType
+{
+  Normal,
+  RelConv,
+};
+
+// Overridable plugin class supporting a series of skeleton functions which get called when
+// the parser parses a given point of interest
+class ParsePlugin
+{
+public:
+  ParsePlugin() : m_owner(nullptr) {}
+  virtual ~ParsePlugin() = default;
+
+  void SetOwner(ParseState* o) { m_owner = o; }
+  void ForwardError(AssemblerError&& err) { m_owner_error = std::move(err); }
+  std::optional<AssemblerError>& Error() { return m_owner_error; }
+
+  virtual void PostParseAction() {}
+
+  // Nonterminal callouts
+  // Pre occurs prior to the head nonterminal being parsed
+  // Post occurs after the nonterminal has been fully parsed
+  virtual void OnDirectivePre(GekkoDirective directive) {}
+  virtual void OnDirectivePost(GekkoDirective directive) {}
+  virtual void OnInstructionPre(const ParseInfo& mnemonic_info, bool extended) {}
+  virtual void OnInstructionPost(const ParseInfo& mnemonic_info, bool extended) {}
+  virtual void OnOperandPre() {}
+  virtual void OnOperandPost() {}
+  virtual void OnResolvedExprPre() {}
+  virtual void OnResolvedExprPost() {}
+
+  // Operator callouts
+  // All occur after the relevant operands have been parsed
+  virtual void OnOperator(AsmOp operation) {}
+
+  // Individual token callouts
+  // All occur prior to the token being parsed
+  // Due to ambiguity of some tokens, an explicit operation is provided
+  virtual void OnTerminal(Terminal type, const AssemblerToken& val) {}
+  virtual void OnHiaddr(std::string_view id) {}
+  virtual void OnLoaddr(std::string_view id) {}
+  virtual void OnOpenParen(ParenType type) {}
+  virtual void OnCloseParen(ParenType type) {}
+  virtual void OnError() {}
+  virtual void OnLabelDecl(std::string_view name) {}
+  virtual void OnVarDecl(std::string_view name) {}
+
+protected:
+  ParseState* m_owner;
+  std::optional<AssemblerError> m_owner_error;
+};
+
+// Parse the provided input with a plugin to handle what to do with certain points of interest
+// e.g. Convert to an IR for generating final machine code, picking up syntactical information
+void ParseWithPlugin(ParsePlugin* plugin, std::string_view input);
+}  // namespace Common::GekkoAssembler::detail

Source/Core/Common/CMakeLists.txt

@@ -1,6 +1,18 @@
 add_library(common
   Analytics.cpp
   Analytics.h
+  Assembler/AssemblerShared.cpp
+  Assembler/AssemblerShared.h
+  Assembler/AssemblerTables.cpp
+  Assembler/AssemblerTables.h
+  Assembler/GekkoAssembler.cpp
+  Assembler/GekkoAssembler.h
+  Assembler/GekkoIRGen.cpp
+  Assembler/GekkoIRGen.h
+  Assembler/GekkoLexer.cpp
+  Assembler/GekkoLexer.h
+  Assembler/GekkoParser.cpp
+  Assembler/GekkoParser.h
   Assert.h
   BitField.h
   BitSet.h

Source/Core/Common/CommonPaths.h

@@ -94,6 +94,7 @@
 #define DYNAMICINPUT_DIR "DynamicInputTextures"
 #define GRAPHICSMOD_DIR "GraphicMods"
 #define WIISDSYNC_DIR "WiiSDSync"
+#define ASSEMBLY_DIR "SavedAssembly"
 
 // This one is only used to remove it if it was present
 #define SHADERCACHE_LEGACY_DIR "ShaderCache"

Source/Core/Common/FileUtil.cpp

@@ -897,6 +897,8 @@ static void RebuildUserDirectories(unsigned int dir_index)
     s_user_paths[D_GBASAVES_IDX] = s_user_paths[D_GBAUSER_IDX] + GBASAVES_DIR DIR_SEP;
     s_user_paths[F_GBABIOS_IDX] = s_user_paths[D_GBAUSER_IDX] + GBA_BIOS;
 
+    s_user_paths[D_ASM_ROOT_IDX] = s_user_paths[D_USER_IDX] + ASSEMBLY_DIR DIR_SEP;
+
     // The shader cache has moved to the cache directory, so remove the old one.
     // TODO: remove that someday.
     File::DeleteDirRecursively(s_user_paths[D_USER_IDX] + SHADERCACHE_LEGACY_DIR DIR_SEP);

Source/Core/Common/FileUtil.h

@@ -71,6 +71,7 @@ enum
   D_GPU_DRIVERS_TMP,
   D_GPU_DRIVERS_HOOKS,
   D_GPU_DRIVERS_FILE_REDIRECT,
+  D_ASM_ROOT_IDX,
   FIRST_FILE_USER_PATH_IDX,
   F_DOLPHINCONFIG_IDX = FIRST_FILE_USER_PATH_IDX,
   F_GCPADCONFIG_IDX,

Source/Core/DolphinQt/CMakeLists.txt

@@ -198,6 +198,12 @@ add_executable(dolphin-emu
   Config/WiimoteControllersWidget.h
   ConvertDialog.cpp
   ConvertDialog.h
+  Debugger/AssembleInstructionDialog.cpp
+  Debugger/AssembleInstructionDialog.h
+  Debugger/AssemblerWidget.cpp
+  Debugger/AssemblerWidget.h
+  Debugger/AssemblyEditor.cpp
+  Debugger/AssemblyEditor.h
   Debugger/BreakpointDialog.cpp
   Debugger/BreakpointDialog.h
   Debugger/BreakpointWidget.cpp
@@ -208,6 +214,8 @@ add_executable(dolphin-emu
   Debugger/CodeViewWidget.h
   Debugger/CodeWidget.cpp
   Debugger/CodeWidget.h
+  Debugger/GekkoSyntaxHighlight.cpp
+  Debugger/GekkoSyntaxHighlight.h
   Debugger/JITWidget.cpp
   Debugger/JITWidget.h
   Debugger/MemoryViewWidget.cpp

Source/Core/DolphinQt/Debugger/AssembleInstructionDialog.cpp

@@ -0,0 +1,129 @@
+// Copyright 2023 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "DolphinQt/Debugger/AssembleInstructionDialog.h"
+
+#include <QDialogButtonBox>
+#include <QFontDatabase>
+#include <QLabel>
+#include <QLineEdit>
+#include <QPushButton>
+#include <QVBoxLayout>
+
+#include "Common/Assembler/GekkoAssembler.h"
+#include "Common/StringUtil.h"
+
+namespace
+{
+QString HtmlFormatErrorLoc(const Common::GekkoAssembler::AssemblerError& err)
+{
+  return QObject::tr("<span style=\"color: red; font-weight: bold\">Error</span> on line %1 col %2")
+      .arg(err.line + 1)
+      .arg(err.col + 1);
+}
+
+QString HtmlFormatErrorLine(const Common::GekkoAssembler::AssemblerError& err)
+{
+  const QString line_pre_error =
+      QString::fromStdString(std::string(err.error_line.substr(0, err.col))).toHtmlEscaped();
+  const QString line_error =
+      QString::fromStdString(std::string(err.error_line.substr(err.col, err.len))).toHtmlEscaped();
+  const QString line_post_error =
+      QString::fromStdString(std::string(err.error_line.substr(err.col + err.len))).toHtmlEscaped();
+
+  return QObject::tr("%1<u><span style=\"color:red; font-weight:bold\">%2</span></u>%3")
+      .arg(line_pre_error)
+      .arg(line_error)
+      .arg(line_post_error);
+}
+}  // namespace
+
+AssembleInstructionDialog::AssembleInstructionDialog(QWidget* parent, u32 address, u32 value)
+    : QDialog(parent), m_code(value), m_address(address)
+{
+  setWindowFlags(windowFlags() & ~Qt::WindowContextHelpButtonHint);
+  setWindowModality(Qt::WindowModal);
+  setWindowTitle(tr("Instruction"));
+
+  CreateWidgets();
+  ConnectWidgets();
+}
+
+void AssembleInstructionDialog::CreateWidgets()
+{
+  auto* layout = new QVBoxLayout;
+
+  m_input_edit = new QLineEdit;
+  m_error_loc_label = new QLabel;
+  m_error_line_label = new QLabel;
+  m_msg_label = new QLabel(tr("No input"));
+  m_button_box = new QDialogButtonBox(QDialogButtonBox::Ok | QDialogButtonBox::Cancel);
+
+  m_error_line_label->setFont(QFont(QFontDatabase::systemFont(QFontDatabase::FixedFont).family()));
+  m_input_edit->setFont(QFont(QFontDatabase::systemFont(QFontDatabase::FixedFont).family()));
+  layout->addWidget(new QLabel(tr("Inline Assembler")));
+  layout->addWidget(m_error_loc_label);
+  layout->addWidget(m_input_edit);
+  layout->addWidget(m_error_line_label);
+  layout->addWidget(m_msg_label);
+  layout->addWidget(m_button_box);
+  m_input_edit->setText(QStringLiteral(".4byte 0x%1").arg(m_code, 8, 16, QLatin1Char('0')));
+
+  setLayout(layout);
+  OnEditChanged();
+}
+
+void AssembleInstructionDialog::ConnectWidgets()
+{
+  connect(m_button_box, &QDialogButtonBox::accepted, this, &QDialog::accept);
+  connect(m_button_box, &QDialogButtonBox::rejected, this, &QDialog::reject);
+
+  connect(m_input_edit, &QLineEdit::textChanged, this, &AssembleInstructionDialog::OnEditChanged);
+}
+
+void AssembleInstructionDialog::OnEditChanged()
+{
+  using namespace Common::GekkoAssembler;
+  std::string line = m_input_edit->text().toStdString();
+  Common::ToLower(&line);
+
+  FailureOr<std::vector<CodeBlock>> asm_result = Assemble(line, m_address);
+
+  if (IsFailure(asm_result))
+  {
+    m_button_box->button(QDialogButtonBox::Ok)->setEnabled(false);
+
+    const AssemblerError& failure = GetFailure(asm_result);
+    m_error_loc_label->setText(HtmlFormatErrorLoc(failure));
+    m_error_line_label->setText(HtmlFormatErrorLine(failure));
+    m_msg_label->setText(QString::fromStdString(failure.message).toHtmlEscaped());
+  }
+  else if (GetT(asm_result).empty() || GetT(asm_result)[0].instructions.empty())
+  {
+    m_button_box->button(QDialogButtonBox::Ok)->setEnabled(false);
+
+    m_error_loc_label->setText(tr("<span style=\"color: red; font-weight: bold\">Error</span>"));
+    m_error_line_label->clear();
+    m_msg_label->setText(tr("No input"));
+  }
+  else
+  {
+    m_button_box->button(QDialogButtonBox::Ok)->setEnabled(true);
+    m_code = 0;
+
+    const std::vector<u8>& block_bytes = GetT(asm_result)[0].instructions;
+    for (size_t i = 0; i < 4 && i < block_bytes.size(); i++)
+    {
+      m_code = (m_code << 8) | block_bytes[i];
+    }
+
+    m_error_loc_label->setText(tr("<span style=\"color: green; font-weight: bold\">Ok</span>"));
+    m_error_line_label->clear();
+    m_msg_label->setText(tr("Instruction: %1").arg(m_code, 8, 16, QLatin1Char('0')));
+  }
+}
+
+u32 AssembleInstructionDialog::GetCode() const
+{
+  return m_code;
+}

Source/Core/DolphinQt/Debugger/AssembleInstructionDialog.h

@@ -0,0 +1,36 @@
+// Copyright 2023 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <QDialog>
+
+#include "Common/CommonTypes.h"
+
+class QDialogButtonBox;
+class QLabel;
+class QLineEdit;
+
+class AssembleInstructionDialog : public QDialog
+{
+  Q_OBJECT
+public:
+  explicit AssembleInstructionDialog(QWidget* parent, u32 address, u32 value);
+
+  u32 GetCode() const;
+
+private:
+  void CreateWidgets();
+  void ConnectWidgets();
+
+  void OnEditChanged();
+
+  u32 m_code;
+  u32 m_address;
+
+  QLineEdit* m_input_edit;
+  QLabel* m_error_loc_label;
+  QLabel* m_error_line_label;
+  QLabel* m_msg_label;
+  QDialogButtonBox* m_button_box;
+};

Source/Core/DolphinQt/Debugger/AssemblerWidget.cpp

@@ -0,0 +1,957 @@
+// Copyright 2023 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "DolphinQt/Debugger/AssemblerWidget.h"
+
+#include <QAction>
+#include <QApplication>
+#include <QClipboard>
+#include <QComboBox>
+#include <QFont>
+#include <QFontDatabase>
+#include <QGridLayout>
+#include <QGroupBox>
+#include <QLabel>
+#include <QLineEdit>
+#include <QMenu>
+#include <QPlainTextEdit>
+#include <QPushButton>
+#include <QScrollBar>
+#include <QShortcut>
+#include <QStyle>
+#include <QTabWidget>
+#include <QTextBlock>
+#include <QTextEdit>
+#include <QToolBar>
+#include <QToolButton>
+
+#include <filesystem>
+#include <fmt/format.h>
+
+#include "Common/Assert.h"
+#include "Common/FileUtil.h"
+
+#include "Core/Core.h"
+#include "Core/PowerPC/MMU.h"
+#include "Core/PowerPC/PowerPC.h"
+#include "Core/System.h"
+
+#include "DolphinQt/Debugger/AssemblyEditor.h"
+#include "DolphinQt/QtUtils/DolphinFileDialog.h"
+#include "DolphinQt/QtUtils/ModalMessageBox.h"
+#include "DolphinQt/Resources.h"
+#include "DolphinQt/Settings.h"
+
+namespace
+{
+using namespace Common::GekkoAssembler;
+
+QString HtmlFormatErrorLoc(const AssemblerError& err)
+{
+  return QObject::tr("<span style=\"color: red; font-weight: bold\">Error</span> on line %1 col %2")
+      .arg(err.line + 1)
+      .arg(err.col + 1);
+}
+
+QString HtmlFormatErrorLine(const AssemblerError& err)
+{
+  const QString line_pre_error =
+      QString::fromStdString(std::string(err.error_line.substr(0, err.col))).toHtmlEscaped();
+  const QString line_error =
+      QString::fromStdString(std::string(err.error_line.substr(err.col, err.len))).toHtmlEscaped();
+  const QString line_post_error =
+      QString::fromStdString(std::string(err.error_line.substr(err.col + err.len))).toHtmlEscaped();
+
+  return QObject::tr("<span style=\"font-family:'monospace';font-size:16px\">"
+                     "<pre>%1<u><span style=\"color:red;font-weight:bold\">%2</span></u>%3</pre>"
+                     "</span>")
+      .arg(line_pre_error)
+      .arg(line_error)
+      .arg(line_post_error);
+}
+
+QString HtmlFormatMessage(const AssemblerError& err)
+{
+  return QObject::tr("<span>%1</span>").arg(QString::fromStdString(err.message).toHtmlEscaped());
+}
+
+void DeserializeBlock(const CodeBlock& blk, std::ostringstream& out_str, bool pad4)
+{
+  size_t i = 0;
+  for (; i < blk.instructions.size(); i++)
+  {
+    out_str << fmt::format("{:02x}", blk.instructions[i]);
+    if (i % 8 == 7)
+    {
+      out_str << '\n';
+    }
+    else if (i % 4 == 3)
+    {
+      out_str << ' ';
+    }
+  }
+  if (pad4)
+  {
+    bool did_pad = false;
+    for (; i % 4 != 0; i++)
+    {
+      out_str << "00";
+      did_pad = true;
+    }
+
+    if (did_pad)
+    {
+      out_str << (i % 8 == 0 ? '\n' : ' ');
+    }
+  }
+  else if (i % 8 != 7)
+  {
+    out_str << '\n';
+  }
+}
+
+void DeserializeToRaw(const std::vector<CodeBlock>& blocks, std::ostringstream& out_str)
+{
+  for (const auto& blk : blocks)
+  {
+    if (blk.instructions.empty())
+    {
+      continue;
+    }
+
+    out_str << fmt::format("# Block {:08x}\n", blk.block_address);
+    DeserializeBlock(blk, out_str, false);
+  }
+}
+
+void DeserializeToAr(const std::vector<CodeBlock>& blocks, std::ostringstream& out_str)
+{
+  for (const auto& blk : blocks)
+  {
+    if (blk.instructions.empty())
+    {
+      continue;
+    }
+
+    size_t i = 0;
+    for (; i < blk.instructions.size() - 3; i += 4)
+    {
+      // type=NormalCode, subtype=SUB_RAM_WRITE, size=32bit
+      const u32 ar_addr = ((blk.block_address + i) & 0x1ffffff) | 0x04000000;
+      out_str << fmt::format("{:08x} {:02x}{:02x}{:02x}{:02x}\n", ar_addr, blk.instructions[i],
+                             blk.instructions[i + 1], blk.instructions[i + 2],
+                             blk.instructions[i + 3]);
+    }
+
+    for (; i < blk.instructions.size(); i++)
+    {
+      // type=NormalCode, subtype=SUB_RAM_WRITE, size=8bit
+      const u32 ar_addr = ((blk.block_address + i) & 0x1ffffff);
+      out_str << fmt::format("{:08x} 000000{:02x}\n", ar_addr, blk.instructions[i]);
+    }
+  }
+}
+
+void DeserializeToGecko(const std::vector<CodeBlock>& blocks, std::ostringstream& out_str)
+{
+  DeserializeToAr(blocks, out_str);
+}
+
+void DeserializeToGeckoExec(const std::vector<CodeBlock>& blocks, std::ostringstream& out_str)
+{
+  for (const auto& blk : blocks)
+  {
+    if (blk.instructions.empty())
+    {
+      continue;
+    }
+
+    u32 nlines = 1 + static_cast<u32>((blk.instructions.size() - 1) / 8);
+    bool ret_on_newline = false;
+    if (blk.instructions.size() % 8 == 0 || blk.instructions.size() % 8 > 4)
+    {
+      // Append extra line for blr
+      nlines++;
+      ret_on_newline = true;
+    }
+
+    out_str << fmt::format("c0000000 {:08x}\n", nlines);
+    DeserializeBlock(blk, out_str, true);
+    if (ret_on_newline)
+    {
+      out_str << "4e800020 00000000\n";
+    }
+    else
+    {
+      out_str << "4e800020\n";
+    }
+  }
+}
+
+void DeserializeToGeckoTramp(const std::vector<CodeBlock>& blocks, std::ostringstream& out_str)
+{
+  for (const auto& blk : blocks)
+  {
+    if (blk.instructions.empty())
+    {
+      continue;
+    }
+
+    const u32 inject_addr = (blk.block_address & 0x1ffffff) | 0x02000000;
+    u32 nlines = 1 + static_cast<u32>((blk.instructions.size() - 1) / 8);
+    bool padding_on_newline = false;
+    if (blk.instructions.size() % 8 == 0 || blk.instructions.size() % 8 > 4)
+    {
+      // Append extra line for nop+branchback
+      nlines++;
+      padding_on_newline = true;
+    }
+
+    out_str << fmt::format("c{:07x} {:08x}\n", inject_addr, nlines);
+    DeserializeBlock(blk, out_str, true);
+    if (padding_on_newline)
+    {
+      out_str << "60000000 00000000\n";
+    }
+    else
+    {
+      out_str << "00000000\n";
+    }
+  }
+}
+}  // namespace
+
+AssemblerWidget::AssemblerWidget(QWidget* parent)
+    : QDockWidget(parent), m_system(Core::System::GetInstance()), m_unnamed_editor_count(0),
+      m_net_zoom_delta(0)
+{
+  {
+    QPalette base_palette;
+    m_dark_scheme = base_palette.color(QPalette::WindowText).value() >
+                    base_palette.color(QPalette::Window).value();
+  }
+
+  setWindowTitle(tr("Assembler"));
+  setObjectName(QStringLiteral("assemblerwidget"));
+
+  setHidden(!Settings::Instance().IsAssemblerVisible() ||
+            !Settings::Instance().IsDebugModeEnabled());
+
+  this->setVisible(true);
+  CreateWidgets();
+
+  restoreGeometry(
+      Settings::GetQSettings().value(QStringLiteral("assemblerwidget/geometry")).toByteArray());
+  setFloating(Settings::GetQSettings().value(QStringLiteral("assemblerwidget/floating")).toBool());
+
+  connect(&Settings::Instance(), &Settings::AssemblerVisibilityChanged, this,
+          [this](bool visible) { setHidden(!visible); });
+
+  connect(&Settings::Instance(), &Settings::DebugModeToggled, this, [this](bool enabled) {
+    setHidden(!enabled || !Settings::Instance().IsAssemblerVisible());
+  });
+
+  connect(&Settings::Instance(), &Settings::EmulationStateChanged, this,
+          &AssemblerWidget::OnEmulationStateChanged);
+  connect(&Settings::Instance(), &Settings::ThemeChanged, this, &AssemblerWidget::UpdateIcons);
+  connect(m_asm_tabs, &QTabWidget::tabCloseRequested, this, &AssemblerWidget::OnTabClose);
+
+  auto* save_shortcut = new QShortcut(QKeySequence::Save, this);
+  // Save should only activate if the active tab is in focus
+  save_shortcut->connect(save_shortcut, &QShortcut::activated, this, [this] {
+    if (m_asm_tabs->currentIndex() != -1 && m_asm_tabs->currentWidget()->hasFocus())
+    {
+      OnSave();
+    }
+  });
+
+  auto* zoom_in_shortcut = new QShortcut(QKeySequence::ZoomIn, this);
+  zoom_in_shortcut->setContext(Qt::WidgetWithChildrenShortcut);
+  connect(zoom_in_shortcut, &QShortcut::activated, this, &AssemblerWidget::OnZoomIn);
+  auto* zoom_out_shortcut = new QShortcut(QKeySequence::ZoomOut, this);
+  zoom_out_shortcut->setContext(Qt::WidgetWithChildrenShortcut);
+  connect(zoom_out_shortcut, &QShortcut::activated, this, &AssemblerWidget::OnZoomOut);
+
+  auto* zoom_in_alternate = new QShortcut(QKeySequence(Qt::CTRL | Qt::Key_Equal), this);
+  zoom_in_alternate->setContext(Qt::WidgetWithChildrenShortcut);
+  connect(zoom_in_alternate, &QShortcut::activated, this, &AssemblerWidget::OnZoomIn);
+  auto* zoom_out_alternate = new QShortcut(QKeySequence(Qt::CTRL | Qt::Key_Underscore), this);
+  zoom_out_alternate->setContext(Qt::WidgetWithChildrenShortcut);
+  connect(zoom_out_alternate, &QShortcut::activated, this, &AssemblerWidget::OnZoomOut);
+
+  auto* zoom_reset = new QShortcut(QKeySequence(Qt::CTRL | Qt::Key_0), this);
+  zoom_reset->setContext(Qt::WidgetWithChildrenShortcut);
+  connect(zoom_reset, &QShortcut::activated, this, &AssemblerWidget::OnZoomReset);
+
+  ConnectWidgets();
+  UpdateIcons();
+}
+
+void AssemblerWidget::closeEvent(QCloseEvent*)
+{
+  Settings::Instance().SetAssemblerVisible(false);
+}
+
+bool AssemblerWidget::ApplicationCloseRequest()
+{
+  int num_unsaved = 0;
+  for (int i = 0; i < m_asm_tabs->count(); i++)
+  {
+    if (GetEditor(i)->IsDirty())
+    {
+      num_unsaved++;
+    }
+  }
+
+  if (num_unsaved > 0)
+  {
+    const int result = ModalMessageBox::question(
+        this, tr("Unsaved Changes"),
+        tr("You have %1 unsaved assembly tabs open\n\n"
+           "Do you want to save all and exit?")
+            .arg(num_unsaved),
+        QMessageBox::YesToAll | QMessageBox::NoToAll | QMessageBox::Cancel, QMessageBox::Cancel);
+    switch (result)
+    {
+    case QMessageBox::YesToAll:
+      for (int i = 0; i < m_asm_tabs->count(); i++)
+      {
+        AsmEditor* editor = GetEditor(i);
+        if (editor->IsDirty())
+        {
+          if (!SaveEditor(editor))
+          {
+            return false;
+          }
+        }
+      }
+      return true;
+    case QMessageBox::NoToAll:
+      return true;
+    case QMessageBox::Cancel:
+      return false;
+    }
+  }
+
+  return true;
+}
+
+AssemblerWidget::~AssemblerWidget()
+{
+  auto& settings = Settings::GetQSettings();
+
+  settings.setValue(QStringLiteral("assemblerwidget/geometry"), saveGeometry());
+  settings.setValue(QStringLiteral("assemblerwidget/floating"), isFloating());
+}
+
+void AssemblerWidget::CreateWidgets()
+{
+  m_asm_tabs = new QTabWidget;
+  m_toolbar = new QToolBar;
+  m_output_type = new QComboBox;
+  m_output_box = new QPlainTextEdit;
+  m_error_box = new QTextEdit;
+  m_address_line = new QLineEdit;
+  m_copy_output_button = new QPushButton;
+
+  m_asm_tabs->setTabsClosable(true);
+
+  // Initialize toolbar and actions
+  // m_toolbar->setIconSize(QSize(32, 32));
+  m_toolbar->setContentsMargins(0, 0, 0, 0);
+  m_toolbar->setToolButtonStyle(Qt::ToolButtonTextBesideIcon);
+
+  m_open = m_toolbar->addAction(tr("Open"), this, &AssemblerWidget::OnOpen);
+  m_new = m_toolbar->addAction(tr("New"), this, &AssemblerWidget::OnNew);
+  m_assemble = m_toolbar->addAction(tr("Assemble"), this, [this] {
+    std::vector<CodeBlock> unused;
+    OnAssemble(&unused);
+  });
+  m_inject = m_toolbar->addAction(tr("Inject"), this, &AssemblerWidget::OnInject);
+  m_save = m_toolbar->addAction(tr("Save"), this, &AssemblerWidget::OnSave);
+
+  m_inject->setEnabled(false);
+  m_save->setEnabled(false);
+  m_assemble->setEnabled(false);
+
+  // Initialize input, output, error text areas
+  auto palette = m_output_box->palette();
+  if (m_dark_scheme)
+  {
+    palette.setColor(QPalette::Base, QColor::fromRgb(76, 76, 76));
+  }
+  else
+  {
+    palette.setColor(QPalette::Base, QColor::fromRgb(180, 180, 180));
+  }
+  m_output_box->setPalette(palette);
+  m_error_box->setPalette(palette);
+
+  QFont mono_font(QFontDatabase::systemFont(QFontDatabase::FixedFont).family());
+  QFont error_font(QFontDatabase::systemFont(QFontDatabase::GeneralFont).family());
+  mono_font.setPointSize(12);
+  error_font.setPointSize(12);
+  QFontMetrics mono_metrics(mono_font);
+  QFontMetrics err_metrics(mono_font);
+
+  m_output_box->setFont(mono_font);
+  m_error_box->setFont(error_font);
+  m_output_box->setReadOnly(true);
+  m_error_box->setReadOnly(true);
+
+  const int output_area_width = mono_metrics.horizontalAdvance(QLatin1Char('0')) * OUTPUT_BOX_WIDTH;
+  m_error_box->setVerticalScrollBarPolicy(Qt::ScrollBarPolicy::ScrollBarAlwaysOff);
+  m_error_box->setFixedHeight(err_metrics.height() * 3 + mono_metrics.height());
+  m_output_box->setFixedWidth(output_area_width);
+  m_error_box->setVerticalScrollBarPolicy(Qt::ScrollBarPolicy::ScrollBarAlwaysOff);
+
+  // Initialize output format selection box
+  m_output_type->addItem(tr("Raw"));
+  m_output_type->addItem(tr("AR Code"));
+  m_output_type->addItem(tr("Gecko (04)"));
+  m_output_type->addItem(tr("Gecko (C0)"));
+  m_output_type->addItem(tr("Gecko (C2)"));
+
+  // Setup layouts
+  auto* addr_input_layout = new QHBoxLayout;
+  addr_input_layout->addWidget(new QLabel(tr("Base Address")));
+  addr_input_layout->addWidget(m_address_line);
+
+  auto* output_extra_layout = new QHBoxLayout;
+  output_extra_layout->addWidget(m_output_type);
+  output_extra_layout->addWidget(m_copy_output_button);
+
+  QWidget* address_input_box = new QWidget();
+  address_input_box->setLayout(addr_input_layout);
+  addr_input_layout->setContentsMargins(0, 0, 0, 0);
+
+  QWidget* output_extra_box = new QWidget();
+  output_extra_box->setFixedWidth(output_area_width);
+  output_extra_box->setLayout(output_extra_layout);
+  output_extra_layout->setContentsMargins(0, 0, 0, 0);
+
+  auto* assembler_layout = new QGridLayout;
+  assembler_layout->setSpacing(0);
+  assembler_layout->setContentsMargins(5, 0, 5, 5);
+  assembler_layout->addWidget(m_toolbar, 0, 0, 1, 2);
+  {
+    auto* input_group = new QGroupBox(tr("Input"));
+    auto* layout = new QVBoxLayout;
+    input_group->setLayout(layout);
+    layout->addWidget(m_asm_tabs);
+    layout->addWidget(address_input_box);
+    assembler_layout->addWidget(input_group, 1, 0, 1, 1);
+  }
+  {
+    auto* output_group = new QGroupBox(tr("Output"));
+    auto* layout = new QGridLayout;
+    output_group->setLayout(layout);
+    layout->addWidget(m_output_box, 0, 0);
+    layout->addWidget(output_extra_box, 1, 0);
+    assembler_layout->addWidget(output_group, 1, 1, 1, 1);
+    output_group->setSizePolicy(
+        QSizePolicy(QSizePolicy::Policy::Fixed, QSizePolicy::Policy::Expanding));
+  }
+  {
+    auto* error_group = new QGroupBox(tr("Error Log"));
+    auto* layout = new QHBoxLayout;
+    error_group->setLayout(layout);
+    layout->addWidget(m_error_box);
+    assembler_layout->addWidget(error_group, 2, 0, 1, 2);
+    error_group->setSizePolicy(
+        QSizePolicy(QSizePolicy::Policy::Expanding, QSizePolicy::Policy::Fixed));
+  }
+
+  QWidget* widget = new QWidget;
+  widget->setLayout(assembler_layout);
+  setWidget(widget);
+}
+
+void AssemblerWidget::ConnectWidgets()
+{
+  m_output_box->connect(m_output_box, &QPlainTextEdit::updateRequest, this, [this] {
+    if (m_output_box->verticalScrollBar()->isVisible())
+    {
+      m_output_box->setFixedWidth(m_output_box->fontMetrics().horizontalAdvance(QLatin1Char('0')) *
+                                      OUTPUT_BOX_WIDTH +
+                                  m_output_box->style()->pixelMetric(QStyle::PM_ScrollBarExtent));
+    }
+    else
+    {
+      m_output_box->setFixedWidth(m_output_box->fontMetrics().horizontalAdvance(QLatin1Char('0')) *
+                                  OUTPUT_BOX_WIDTH);
+    }
+  });
+  m_copy_output_button->connect(m_copy_output_button, &QPushButton::released, this,
+                                &AssemblerWidget::OnCopyOutput);
+  m_address_line->connect(m_address_line, &QLineEdit::textChanged, this,
+                          &AssemblerWidget::OnBaseAddressChanged);
+  m_asm_tabs->connect(m_asm_tabs, &QTabWidget::currentChanged, this, &AssemblerWidget::OnTabChange);
+}
+
+void AssemblerWidget::OnAssemble(std::vector<CodeBlock>* asm_out)
+{
+  if (m_asm_tabs->currentIndex() == -1)
+  {
+    return;
+  }
+  AsmEditor* active_editor = GetEditor(m_asm_tabs->currentIndex());
+
+  AsmKind kind = AsmKind::Raw;
+  m_error_box->clear();
+  m_output_box->clear();
+  switch (m_output_type->currentIndex())
+  {
+  case 0:
+    kind = AsmKind::Raw;
+    break;
+  case 1:
+    kind = AsmKind::ActionReplay;
+    break;
+  case 2:
+    kind = AsmKind::Gecko;
+    break;
+  case 3:
+    kind = AsmKind::GeckoExec;
+    break;
+  case 4:
+    kind = AsmKind::GeckoTrampoline;
+    break;
+  }
+
+  bool good;
+  u32 base_address = m_address_line->text().toUInt(&good, 16);
+  if (!good)
+  {
+    base_address = 0;
+    m_error_box->append(
+        tr("<span style=\"color:#ffcc00\">Warning</span> invalid base address, defaulting to 0"));
+  }
+
+  const std::string contents = active_editor->toPlainText().toStdString();
+  auto result = Assemble(contents, base_address);
+  if (IsFailure(result))
+  {
+    m_error_box->clear();
+    asm_out->clear();
+
+    const AssemblerError& error = GetFailure(result);
+    m_error_box->append(HtmlFormatErrorLoc(error));
+    m_error_box->append(HtmlFormatErrorLine(error));
+    m_error_box->append(HtmlFormatMessage(error));
+    asm_out->clear();
+    return;
+  }
+
+  auto& blocks = GetT(result);
+  std::ostringstream str_contents;
+  switch (kind)
+  {
+  case AsmKind::Raw:
+    DeserializeToRaw(blocks, str_contents);
+    break;
+  case AsmKind::ActionReplay:
+    DeserializeToAr(blocks, str_contents);
+    break;
+  case AsmKind::Gecko:
+    DeserializeToGecko(blocks, str_contents);
+    break;
+  case AsmKind::GeckoExec:
+    DeserializeToGeckoExec(blocks, str_contents);
+    break;
+  case AsmKind::GeckoTrampoline:
+    DeserializeToGeckoTramp(blocks, str_contents);
+    break;
+  }
+
+  m_output_box->appendPlainText(QString::fromStdString(str_contents.str()));
+  m_output_box->moveCursor(QTextCursor::MoveOperation::Start);
+  m_output_box->ensureCursorVisible();
+
+  *asm_out = std::move(GetT(result));
+}
+
+void AssemblerWidget::OnCopyOutput()
+{
+  QApplication::clipboard()->setText(m_output_box->toPlainText());
+}
+
+void AssemblerWidget::OnOpen()
+{
+  const std::string default_dir = File::GetUserPath(D_ASM_ROOT_IDX);
+  const QStringList paths = DolphinFileDialog::getOpenFileNames(
+      this, tr("Select a File"), QString::fromStdString(default_dir),
+      QStringLiteral("%1 (*.s *.S *.asm);;%2 (*)")
+          .arg(tr("All Assembly files"))
+          .arg(tr("All Files")));
+  if (paths.isEmpty())
+  {
+    return;
+  }
+
+  std::optional<int> show_index;
+  for (auto path : paths)
+  {
+    show_index = std::nullopt;
+    for (int i = 0; i < m_asm_tabs->count(); i++)
+    {
+      AsmEditor* editor = GetEditor(i);
+      if (editor->PathsMatch(path))
+      {
+        show_index = i;
+        break;
+      }
+    }
+
+    if (!show_index)
+    {
+      NewEditor(path);
+    }
+  }
+
+  if (show_index)
+  {
+    m_asm_tabs->setCurrentIndex(*show_index);
+  }
+}
+
+void AssemblerWidget::OnNew()
+{
+  NewEditor();
+}
+
+void AssemblerWidget::OnInject()
+{
+  Core::CPUThreadGuard guard(m_system);
+
+  std::vector<CodeBlock> asm_result;
+  OnAssemble(&asm_result);
+  for (const auto& blk : asm_result)
+  {
+    if (!PowerPC::MMU::HostIsRAMAddress(guard, blk.block_address) || blk.instructions.empty())
+    {
+      continue;
+    }
+
+    m_system.GetPowerPC().GetDebugInterface().SetPatch(guard, blk.block_address, blk.instructions);
+  }
+}
+
+void AssemblerWidget::OnSave()
+{
+  if (m_asm_tabs->currentIndex() == -1)
+  {
+    return;
+  }
+  AsmEditor* active_editor = GetEditor(m_asm_tabs->currentIndex());
+
+  SaveEditor(active_editor);
+}
+
+void AssemblerWidget::OnZoomIn()
+{
+  if (m_asm_tabs->currentIndex() != -1)
+  {
+    ZoomAllEditors(2);
+  }
+}
+
+void AssemblerWidget::OnZoomOut()
+{
+  if (m_asm_tabs->currentIndex() != -1)
+  {
+    ZoomAllEditors(-2);
+  }
+}
+
+void AssemblerWidget::OnZoomReset()
+{
+  if (m_asm_tabs->currentIndex() != -1)
+  {
+    ZoomAllEditors(-m_net_zoom_delta);
+  }
+}
+
+void AssemblerWidget::OnBaseAddressChanged()
+{
+  if (m_asm_tabs->currentIndex() == -1)
+  {
+    return;
+  }
+  AsmEditor* active_editor = GetEditor(m_asm_tabs->currentIndex());
+
+  active_editor->SetBaseAddress(m_address_line->text());
+}
+
+void AssemblerWidget::OnTabChange(int index)
+{
+  if (index == -1)
+  {
+    m_address_line->clear();
+    return;
+  }
+  AsmEditor* active_editor = GetEditor(index);
+
+  m_address_line->setText(active_editor->BaseAddress());
+}
+
+QString AssemblerWidget::TabTextForEditor(AsmEditor* editor, bool with_dirty)
+{
+  ASSERT(editor != nullptr);
+  QString dirtyFlag = QStringLiteral();
+  if (editor->IsDirty() && with_dirty)
+  {
+    dirtyFlag = QStringLiteral(" *");
+  }
+
+  if (editor->Path().isEmpty())
+  {
+    if (editor->EditorNum() == 0)
+    {
+      return tr("New File%1").arg(dirtyFlag);
+    }
+    return tr("New File (%1)%2").arg(editor->EditorNum() + 1).arg(dirtyFlag);
+  }
+  return tr("%1%2").arg(editor->EditorTitle()).arg(dirtyFlag);
+}
+
+AsmEditor* AssemblerWidget::GetEditor(int idx)
+{
+  return qobject_cast<AsmEditor*>(m_asm_tabs->widget(idx));
+}
+
+void AssemblerWidget::NewEditor(const QString& path)
+{
+  AsmEditor* new_editor =
+      new AsmEditor(path, path.isEmpty() ? AllocateTabNum() : INVALID_EDITOR_NUM, m_dark_scheme);
+  if (!path.isEmpty() && !new_editor->LoadFromPath())
+  {
+    ModalMessageBox::warning(this, tr("Failed to open file"),
+                             tr("Failed to read the contents of file\n\n"
+                                "\"%1\"")
+                                 .arg(path));
+    delete new_editor;
+    return;
+  }
+
+  const int tab_idx = m_asm_tabs->addTab(new_editor, QStringLiteral());
+  new_editor->connect(new_editor, &AsmEditor::PathChanged, this, [this] {
+    AsmEditor* updated_tab = qobject_cast<AsmEditor*>(sender());
+    DisambiguateTabTitles(updated_tab);
+    UpdateTabText(updated_tab);
+  });
+  new_editor->connect(new_editor, &AsmEditor::DirtyChanged, this,
+                      [this] { UpdateTabText(qobject_cast<AsmEditor*>(sender())); });
+  new_editor->connect(new_editor, &AsmEditor::ZoomRequested, this,
+                      &AssemblerWidget::ZoomAllEditors);
+  new_editor->Zoom(m_net_zoom_delta);
+
+  DisambiguateTabTitles(new_editor);
+
+  m_asm_tabs->setTabText(tab_idx, TabTextForEditor(new_editor, true));
+
+  if (m_save && m_assemble)
+  {
+    m_save->setEnabled(true);
+    m_assemble->setEnabled(true);
+  }
+
+  m_asm_tabs->setCurrentIndex(tab_idx);
+}
+
+bool AssemblerWidget::SaveEditor(AsmEditor* editor)
+{
+  QString save_path = editor->Path();
+  if (save_path.isEmpty())
+  {
+    const std::string default_dir = File::GetUserPath(D_ASM_ROOT_IDX);
+    const QString asm_filter = QStringLiteral("%1 (*.S)").arg(tr("Assembly File"));
+    const QString all_filter = QStringLiteral("%2 (*)").arg(tr("All Files"));
+
+    QString selected_filter;
+    save_path = DolphinFileDialog::getSaveFileName(
+        this, tr("Save File to"), QString::fromStdString(default_dir),
+        QStringLiteral("%1;;%2").arg(asm_filter).arg(all_filter), &selected_filter);
+
+    if (save_path.isEmpty())
+    {
+      return false;
+    }
+
+    if (selected_filter == asm_filter &&
+        std::filesystem::path(save_path.toStdString()).extension().empty())
+    {
+      save_path.append(QStringLiteral(".S"));
+    }
+  }
+
+  editor->SaveFile(save_path);
+  return true;
+}
+
+void AssemblerWidget::OnEmulationStateChanged(Core::State state)
+{
+  m_inject->setEnabled(state != Core::State::Uninitialized);
+}
+
+void AssemblerWidget::OnTabClose(int index)
+{
+  ASSERT(index < m_asm_tabs->count());
+  AsmEditor* editor = GetEditor(index);
+
+  if (editor->IsDirty())
+  {
+    const int result = ModalMessageBox::question(
+        this, tr("Unsaved Changes"),
+        tr("There are unsaved changes in \"%1\".\n\n"
+           "Do you want to save before closing?")
+            .arg(TabTextForEditor(editor, false)),
+        QMessageBox::Yes | QMessageBox::No | QMessageBox::Cancel, QMessageBox::Cancel);
+    switch (result)
+    {
+    case QMessageBox::Yes:
+      if (editor->IsDirty())
+      {
+        if (!SaveEditor(editor))
+        {
+          return;
+        }
+      }
+      break;
+    case QMessageBox::No:
+      break;
+    case QMessageBox::Cancel:
+      return;
+    }
+  }
+
+  CloseTab(index, editor);
+}
+
+void AssemblerWidget::CloseTab(int index, AsmEditor* editor)
+{
+  FreeTabNum(editor->EditorNum());
+
+  m_asm_tabs->removeTab(index);
+  editor->deleteLater();
+
+  DisambiguateTabTitles(nullptr);
+
+  if (m_asm_tabs->count() == 0 && m_save && m_assemble)
+  {
+    m_save->setEnabled(false);
+    m_assemble->setEnabled(false);
+  }
+}
+
+int AssemblerWidget::AllocateTabNum()
+{
+  auto min_it = std::min_element(m_free_editor_nums.begin(), m_free_editor_nums.end());
+  if (min_it == m_free_editor_nums.end())
+  {
+    return m_unnamed_editor_count++;
+  }
+
+  const int min = *min_it;
+  m_free_editor_nums.erase(min_it);
+  return min;
+}
+
+void AssemblerWidget::FreeTabNum(int num)
+{
+  if (num != INVALID_EDITOR_NUM)
+  {
+    m_free_editor_nums.push_back(num);
+  }
+}
+
+void AssemblerWidget::UpdateTabText(AsmEditor* editor)
+{
+  int tab_idx = 0;
+  for (; tab_idx < m_asm_tabs->count(); tab_idx++)
+  {
+    if (m_asm_tabs->widget(tab_idx) == editor)
+    {
+      break;
+    }
+  }
+  ASSERT(tab_idx < m_asm_tabs->count());
+
+  m_asm_tabs->setTabText(tab_idx, TabTextForEditor(editor, true));
+}
+
+void AssemblerWidget::DisambiguateTabTitles(AsmEditor* new_tab)
+{
+  for (int i = 0; i < m_asm_tabs->count(); i++)
+  {
+    AsmEditor* check = GetEditor(i);
+    if (check->IsAmbiguous())
+    {
+      // Could group all editors with matching titles in a linked list
+      // but tracking that nicely without dangling pointers feels messy
+      bool still_ambiguous = false;
+      for (int j = 0; j < m_asm_tabs->count(); j++)
+      {
+        AsmEditor* against = GetEditor(j);
+        if (j != i && check->FileName() == against->FileName())
+        {
+          if (!against->IsAmbiguous())
+          {
+            against->SetAmbiguous(true);
+            UpdateTabText(against);
+          }
+          still_ambiguous = true;
+        }
+      }
+
+      if (!still_ambiguous)
+      {
+        check->SetAmbiguous(false);
+        UpdateTabText(check);
+      }
+    }
+  }
+
+  if (new_tab != nullptr)
+  {
+    bool is_ambiguous = false;
+    for (int i = 0; i < m_asm_tabs->count(); i++)
+    {
+      AsmEditor* against = GetEditor(i);
+      if (new_tab != against && against->FileName() == new_tab->FileName())
+      {
+        against->SetAmbiguous(true);
+        UpdateTabText(against);
+        is_ambiguous = true;
+      }
+    }
+
+    if (is_ambiguous)
+    {
+      new_tab->SetAmbiguous(true);
+      UpdateTabText(new_tab);
+    }
+  }
+}
+
+void AssemblerWidget::UpdateIcons()
+{
+  m_new->setIcon(Resources::GetThemeIcon("assembler_new"));
+  m_open->setIcon(Resources::GetThemeIcon("assembler_openasm"));
+  m_save->setIcon(Resources::GetThemeIcon("assembler_save"));
+  m_assemble->setIcon(Resources::GetThemeIcon("assembler_assemble"));
+  m_inject->setIcon(Resources::GetThemeIcon("assembler_inject"));
+  m_copy_output_button->setIcon(Resources::GetThemeIcon("assembler_clipboard"));
+}
+
+void AssemblerWidget::ZoomAllEditors(int amount)
+{
+  if (amount != 0)
+  {
+    m_net_zoom_delta += amount;
+    for (int i = 0; i < m_asm_tabs->count(); i++)
+    {
+      GetEditor(i)->Zoom(amount);
+    }
+  }
+}

Source/Core/DolphinQt/Debugger/AssemblerWidget.h

@@ -0,0 +1,100 @@
+// Copyright 2023 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <QDockWidget>
+
+#include "Common/Assembler/GekkoAssembler.h"
+#include "Core/Core.h"
+
+class QTabWidget;
+class AsmEditor;
+class QAction;
+class QComboBox;
+class QLineEdit;
+class QPlainTextEdit;
+class QPushButton;
+class QTextEdit;
+class QToolBar;
+
+namespace Core
+{
+class System;
+}  // namespace Core
+
+class AssemblerWidget : public QDockWidget
+{
+  Q_OBJECT
+public:
+  explicit AssemblerWidget(QWidget* parent);
+
+  bool ApplicationCloseRequest();
+
+  ~AssemblerWidget();
+
+protected:
+  void closeEvent(QCloseEvent*);
+
+private:
+  enum class AsmKind
+  {
+    Raw,
+    ActionReplay,
+    Gecko,
+    GeckoExec,
+    GeckoTrampoline
+  };
+  static constexpr int OUTPUT_BOX_WIDTH = 18;
+  void CreateWidgets();
+  void ConnectWidgets();
+
+  void OnEditChanged();
+
+  void OnAssemble(std::vector<Common::GekkoAssembler::CodeBlock>* asm_out);
+  void OnCopyOutput();
+  void OnOpen();
+  void OnNew();
+  void OnInject();
+  void OnSave();
+  void OnZoomIn();
+  void OnZoomOut();
+  void OnZoomReset();
+  void OnBaseAddressChanged();
+  void OnTabChange(int index);
+  QString TabTextForEditor(AsmEditor* editor, bool with_dirty);
+  AsmEditor* GetEditor(int idx);
+  void NewEditor(const QString& path = QStringLiteral());
+  bool SaveEditor(AsmEditor* editor);
+  void OnEmulationStateChanged(Core::State state);
+  void OnTabClose(int index);
+  void CloseTab(int index, AsmEditor* editor);
+  int AllocateTabNum();
+  void FreeTabNum(int num);
+  void UpdateTabText(AsmEditor* editor);
+  void DisambiguateTabTitles(AsmEditor* editor);
+  void UpdateIcons();
+  void ZoomAllEditors(int amount);
+
+  static constexpr int INVALID_EDITOR_NUM = -1;
+
+  Core::System& m_system;
+
+  QTabWidget* m_asm_tabs;
+  QPlainTextEdit* m_output_box;
+  QComboBox* m_output_type;
+  QPushButton* m_copy_output_button;
+  QTextEdit* m_error_box;
+  QLineEdit* m_address_line;
+  QToolBar* m_toolbar;
+  QAction* m_open;
+  QAction* m_new;
+  QAction* m_assemble;
+  QAction* m_inject;
+  QAction* m_save;
+
+  std::list<int> m_free_editor_nums;
+  int m_unnamed_editor_count;
+  int m_net_zoom_delta;
+  bool m_dark_scheme;
+};

Source/Core/DolphinQt/Debugger/AssemblyEditor.cpp

@@ -0,0 +1,369 @@
+// Copyright 2023 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "DolphinQt/Debugger/AssemblyEditor.h"
+
+#include <QFile>
+#include <QPainter>
+#include <QTextBlock>
+#include <QToolTip>
+
+#include <filesystem>
+
+#include "Common/Assembler/GekkoParser.h"
+#include "Common/StringUtil.h"
+#include "DolphinQt/Debugger/GekkoSyntaxHighlight.h"
+
+QSize AsmEditor::LineNumberArea::sizeHint() const
+{
+  return QSize(asm_editor->LineNumberAreaWidth(), 0);
+}
+
+void AsmEditor::LineNumberArea::paintEvent(QPaintEvent* event)
+{
+  asm_editor->LineNumberAreaPaintEvent(event);
+}
+
+AsmEditor::AsmEditor(const QString& path, int editor_num, bool dark_scheme, QWidget* parent)
+    : QPlainTextEdit(parent), m_path(path), m_base_address(QStringLiteral("0")),
+      m_editor_num(editor_num), m_dirty(false), m_dark_scheme(dark_scheme)
+{
+  if (!m_path.isEmpty())
+  {
+    m_filename =
+        QString::fromStdString(std::filesystem::path(m_path.toStdString()).filename().string());
+  }
+
+  m_line_number_area = new LineNumberArea(this);
+  m_highlighter = new GekkoSyntaxHighlight(document(), currentCharFormat(), dark_scheme);
+  m_last_block = textCursor().block();
+
+  QFont mono_font(QFontDatabase::systemFont(QFontDatabase::FixedFont).family());
+  mono_font.setPointSize(12);
+  setFont(mono_font);
+  m_line_number_area->setFont(mono_font);
+
+  UpdateLineNumberAreaWidth(0);
+  HighlightCurrentLine();
+  setMouseTracking(true);
+
+  connect(this, &AsmEditor::blockCountChanged, this, &AsmEditor::UpdateLineNumberAreaWidth);
+  connect(this, &AsmEditor::updateRequest, this, &AsmEditor::UpdateLineNumberArea);
+  connect(this, &AsmEditor::cursorPositionChanged, this, &AsmEditor::HighlightCurrentLine);
+  connect(this, &AsmEditor::textChanged, this, [this] {
+    m_dirty = true;
+    emit DirtyChanged();
+  });
+}
+
+int AsmEditor::LineNumberAreaWidth()
+{
+  int num_digits = 1;
+  for (int max = qMax(1, blockCount()); max >= 10; max /= 10, ++num_digits)
+  {
+  }
+
+  return 3 + CharWidth() * qMax(2, num_digits);
+}
+
+void AsmEditor::SetBaseAddress(const QString& ba)
+{
+  if (ba != m_base_address)
+  {
+    m_base_address = ba;
+    m_dirty = true;
+    emit DirtyChanged();
+  }
+}
+
+bool AsmEditor::LoadFromPath()
+{
+  QFile file(m_path);
+  if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
+  {
+    return false;
+  }
+
+  const std::string base_addr_line = file.readLine().toStdString();
+  std::string base_address = "";
+  for (size_t i = 0; i < base_addr_line.length(); i++)
+  {
+    if (std::isspace(base_addr_line[i]))
+    {
+      continue;
+    }
+    else if (base_addr_line[i] == '#')
+    {
+      base_address = base_addr_line.substr(i + 1);
+      break;
+    }
+    else
+    {
+      break;
+    }
+  }
+
+  if (base_address.empty())
+  {
+    file.seek(0);
+  }
+  else
+  {
+    StringPopBackIf(&base_address, '\n');
+    if (base_address.empty())
+    {
+      base_address = "0";
+    }
+    m_base_address = QString::fromStdString(base_address);
+  }
+
+  const bool old_block = blockSignals(true);
+  setPlainText(QString::fromStdString(file.readAll().toStdString()));
+  blockSignals(old_block);
+  return true;
+}
+
+bool AsmEditor::PathsMatch(const QString& path) const
+{
+  if (m_path.isEmpty() || path.isEmpty())
+  {
+    return false;
+  }
+  return std::filesystem::path(m_path.toStdString()) == std::filesystem::path(path.toStdString());
+}
+
+void AsmEditor::Zoom(int amount)
+{
+  if (amount > 0)
+  {
+    zoomIn(amount);
+  }
+  else
+  {
+    zoomOut(-amount);
+  }
+  m_line_number_area->setFont(font());
+}
+
+bool AsmEditor::SaveFile(const QString& save_path)
+{
+  QFile file(save_path);
+  if (!file.open(QIODevice::WriteOnly | QIODevice::Text | QIODevice::Truncate))
+  {
+    return false;
+  }
+
+  if (m_path != save_path)
+  {
+    m_path = save_path;
+    m_filename =
+        QString::fromStdString(std::filesystem::path(m_path.toStdString()).filename().string());
+    emit PathChanged();
+  }
+
+  if (file.write(QStringLiteral("#%1\n").arg(m_base_address).toUtf8()) == -1)
+  {
+    return false;
+  }
+
+  if (file.write(toPlainText().toUtf8()) == -1)
+  {
+    return false;
+  }
+
+  m_dirty = false;
+  emit DirtyChanged();
+  return true;
+}
+
+void AsmEditor::UpdateLineNumberAreaWidth(int)
+{
+  setViewportMargins(LineNumberAreaWidth(), 0, 0, 0);
+}
+
+void AsmEditor::UpdateLineNumberArea(const QRect& rect, int dy)
+{
+  if (dy != 0)
+  {
+    m_line_number_area->scroll(0, dy);
+  }
+  else
+  {
+    m_line_number_area->update(0, rect.y(), m_line_number_area->width(), rect.height());
+  }
+
+  if (rect.contains(viewport()->rect()))
+  {
+    UpdateLineNumberAreaWidth(0);
+  }
+}
+
+int AsmEditor::CharWidth() const
+{
+  return fontMetrics().horizontalAdvance(QLatin1Char(' '));
+}
+
+void AsmEditor::resizeEvent(QResizeEvent* e)
+{
+  QPlainTextEdit::resizeEvent(e);
+
+  const QRect cr = contentsRect();
+  m_line_number_area->setGeometry(QRect(cr.left(), cr.top(), LineNumberAreaWidth(), cr.height()));
+}
+
+void AsmEditor::paintEvent(QPaintEvent* event)
+{
+  QPlainTextEdit::paintEvent(event);
+
+  QPainter painter(viewport());
+  QTextCursor tc(document());
+
+  QPen p = QPen(Qt::red);
+  p.setStyle(Qt::PenStyle::SolidLine);
+  p.setWidth(1);
+  painter.setPen(p);
+  const int width = CharWidth();
+
+  for (QTextBlock blk = firstVisibleBlock(); blk.isVisible() && blk.isValid(); blk = blk.next())
+  {
+    if (blk.userData() == nullptr)
+    {
+      continue;
+    }
+
+    BlockInfo* info = static_cast<BlockInfo*>(blk.userData());
+    if (info->error_at_eol)
+    {
+      tc.setPosition(blk.position() + blk.length() - 1);
+      tc.clearSelection();
+      const QRect qr = cursorRect(tc);
+      painter.drawLine(qr.x(), qr.y() + qr.height(), qr.x() + width, qr.y() + qr.height());
+    }
+  }
+}
+
+bool AsmEditor::event(QEvent* e)
+{
+  if (e->type() == QEvent::ToolTip)
+  {
+    QHelpEvent* he = static_cast<QHelpEvent*>(e);
+    QTextCursor hover_cursor = cursorForPosition(he->pos());
+    QTextBlock hover_block = hover_cursor.block();
+
+    BlockInfo* info = static_cast<BlockInfo*>(hover_block.userData());
+    if (info == nullptr || !info->error)
+    {
+      QToolTip::hideText();
+      return true;
+    }
+
+    QRect check_rect;
+    if (info->error_at_eol)
+    {
+      hover_cursor.setPosition(hover_block.position() +
+                               static_cast<int>(info->error->col + info->error->len));
+      const QRect cursor_left = cursorRect(hover_cursor);
+      const int area_width = CharWidth();
+      check_rect = QRect(cursor_left.x() + LineNumberAreaWidth(), cursor_left.y(),
+                         cursor_left.x() + area_width, cursor_left.height());
+    }
+    else
+    {
+      hover_cursor.setPosition(hover_block.position() + static_cast<int>(info->error->col));
+      const QRect cursor_left = cursorRect(hover_cursor);
+      hover_cursor.setPosition(hover_block.position() +
+                               static_cast<int>(info->error->col + info->error->len));
+      const QRect cursor_right = cursorRect(hover_cursor);
+      check_rect = QRect(cursor_left.x() + LineNumberAreaWidth(), cursor_left.y(),
+                         cursor_right.x() - cursor_left.x(), cursor_left.height());
+    }
+    if (check_rect.contains(he->pos()))
+    {
+      QToolTip::showText(he->globalPos(), QString::fromStdString(info->error->message));
+    }
+    else
+    {
+      QToolTip::hideText();
+    }
+    return true;
+  }
+  return QPlainTextEdit::event(e);
+}
+
+void AsmEditor::keyPressEvent(QKeyEvent* event)
+{
+  // HACK: Change shift+enter to enter to keep lines as blocks
+  if (event->modifiers() & Qt::ShiftModifier &&
+      (event->key() == Qt::Key_Enter || event->key() == Qt::Key_Return))
+  {
+    event->setModifiers(event->modifiers() & ~Qt::ShiftModifier);
+  }
+  QPlainTextEdit::keyPressEvent(event);
+}
+
+void AsmEditor::wheelEvent(QWheelEvent* event)
+{
+  QPlainTextEdit::wheelEvent(event);
+
+  if (event->modifiers() & Qt::ControlModifier)
+  {
+    auto delta = static_cast<int>(std::round((event->angleDelta().y() / 120.0)));
+    if (delta != 0)
+    {
+      emit ZoomRequested(delta);
+    }
+  }
+}
+
+void AsmEditor::HighlightCurrentLine()
+{
+  const bool old_state = blockSignals(true);
+
+  if (m_last_block.blockNumber() != textCursor().blockNumber())
+  {
+    m_highlighter->SetMode(2);
+    m_highlighter->rehighlightBlock(m_last_block);
+
+    m_last_block = textCursor().block();
+  }
+
+  m_highlighter->SetCursorLoc(textCursor().positionInBlock());
+  m_highlighter->SetMode(1);
+  m_highlighter->rehighlightBlock(textCursor().block());
+  m_highlighter->SetMode(0);
+
+  blockSignals(old_state);
+}
+
+void AsmEditor::LineNumberAreaPaintEvent(QPaintEvent* event)
+{
+  QPainter painter(m_line_number_area);
+  if (m_dark_scheme)
+  {
+    painter.fillRect(event->rect(), QColor::fromRgb(76, 76, 76));
+  }
+  else
+  {
+    painter.fillRect(event->rect(), QColor::fromRgb(180, 180, 180));
+  }
+
+  QTextBlock block = firstVisibleBlock();
+  int block_num = block.blockNumber();
+  int top = qRound(blockBoundingGeometry(block).translated(contentOffset()).top());
+  int bottom = top + qRound(blockBoundingRect(block).height());
+
+  while (block.isValid() && top <= event->rect().bottom())
+  {
+    if (block.isVisible() && bottom >= event->rect().top())
+    {
+      const QString num = QString::number(block_num + 1);
+      painter.drawText(0, top, m_line_number_area->width(), fontMetrics().height(), Qt::AlignRight,
+                       num);
+    }
+
+    block = block.next();
+    top = bottom;
+    bottom = top + qRound(blockBoundingRect(block).height());
+    ++block_num;
+  }
+}

Source/Core/DolphinQt/Debugger/AssemblyEditor.h

@@ -0,0 +1,81 @@
+// Copyright 2023 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <QPlainTextEdit>
+#include <QTextBlock>
+
+class QWidget;
+class QPaintEvent;
+class QResizeEvent;
+class QRect;
+class QWheelEvent;
+class GekkoSyntaxHighlight;
+
+class AsmEditor : public QPlainTextEdit
+{
+  Q_OBJECT;
+
+public:
+  AsmEditor(const QString& file_path, int editor_num, bool dark_scheme, QWidget* parent = nullptr);
+  void LineNumberAreaPaintEvent(QPaintEvent* event);
+  int LineNumberAreaWidth();
+  const QString& Path() const { return m_path; }
+  const QString& FileName() const { return m_filename; }
+  const QString& EditorTitle() const { return m_title_ambiguous ? Path() : FileName(); }
+  const QString& BaseAddress() const { return m_base_address; }
+  void SetBaseAddress(const QString& ba);
+  void SetAmbiguous(bool b) { m_title_ambiguous = b; }
+  int EditorNum() const { return m_editor_num; }
+  bool LoadFromPath();
+  bool IsDirty() const { return m_dirty; }
+  bool IsAmbiguous() const { return m_title_ambiguous; }
+  bool PathsMatch(const QString& path) const;
+  void Zoom(int amount);
+
+public slots:
+  bool SaveFile(const QString& save_path);
+
+signals:
+  void PathChanged();
+  void DirtyChanged();
+  void ZoomRequested(int amount);
+
+protected:
+  void resizeEvent(QResizeEvent* event) override;
+  void paintEvent(QPaintEvent* event) override;
+  bool event(QEvent* e) override;
+  void keyPressEvent(QKeyEvent* event) override;
+  void wheelEvent(QWheelEvent* event) override;
+
+private:
+  void UpdateLineNumberAreaWidth(int new_block_count);
+  void HighlightCurrentLine();
+  void UpdateLineNumberArea(const QRect& rect, int dy);
+  int CharWidth() const;
+
+  class LineNumberArea : public QWidget
+  {
+  public:
+    LineNumberArea(AsmEditor* editor) : QWidget(editor), asm_editor(editor) {}
+    QSize sizeHint() const override;
+
+  protected:
+    void paintEvent(QPaintEvent* event) override;
+
+  private:
+    AsmEditor* asm_editor;
+  };
+
+  QWidget* m_line_number_area;
+  GekkoSyntaxHighlight* m_highlighter;
+  QString m_path;
+  QString m_filename;
+  QString m_base_address;
+  const int m_editor_num;
+  bool m_dirty;
+  QTextBlock m_last_block;
+  bool m_title_ambiguous;
+  bool m_dark_scheme;
+};

Source/Core/DolphinQt/Debugger/CodeViewWidget.cpp

@@ -35,6 +35,7 @@
 #include "Core/PowerPC/PPCSymbolDB.h"
 #include "Core/PowerPC/PowerPC.h"
 #include "Core/System.h"
+#include "DolphinQt/Debugger/AssembleInstructionDialog.h"
 #include "DolphinQt/Debugger/PatchInstructionDialog.h"
 #include "DolphinQt/Host.h"
 #include "DolphinQt/QtUtils/SetWindowDecorations.h"
@@ -597,6 +598,8 @@ void CodeViewWidget::OnContextMenu()
   auto* insert_nop_action = menu->addAction(tr("Insert &nop"), this, &CodeViewWidget::OnInsertNOP);
   auto* replace_action =
       menu->addAction(tr("Re&place instruction"), this, &CodeViewWidget::OnReplaceInstruction);
+  auto* assemble_action =
+      menu->addAction(tr("Assemble instruction"), this, &CodeViewWidget::OnAssembleInstruction);
   auto* restore_action =
       menu->addAction(tr("Restore instruction"), this, &CodeViewWidget::OnRestoreInstruction);
 
@@ -637,8 +640,9 @@ void CodeViewWidget::OnContextMenu()
   run_until_menu->setEnabled(!target.isEmpty());
   follow_branch_action->setEnabled(follow_branch_enabled);
 
-  for (auto* action : {copy_address_action, copy_line_action, copy_hex_action, function_action,
-                       ppc_action, insert_blr_action, insert_nop_action, replace_action})
+  for (auto* action :
+       {copy_address_action, copy_line_action, copy_hex_action, function_action, ppc_action,
+        insert_blr_action, insert_nop_action, replace_action, assemble_action})
   {
     action->setEnabled(running);
   }
@@ -997,8 +1001,17 @@ void CodeViewWidget::OnSetSymbolEndAddress()
 
 void CodeViewWidget::OnReplaceInstruction()
 {
-  Core::CPUThreadGuard guard(m_system);
+  DoPatchInstruction(false);
+}
 
+void CodeViewWidget::OnAssembleInstruction()
+{
+  DoPatchInstruction(true);
+}
+
+void CodeViewWidget::DoPatchInstruction(bool assemble)
+{
+  Core::CPUThreadGuard guard(m_system);
   const u32 addr = GetContextAddress();
 
   if (!PowerPC::MMU::HostIsInstructionRAMAddress(guard, addr))
@@ -1010,14 +1023,27 @@ void CodeViewWidget::OnReplaceInstruction()
     return;
 
   auto& debug_interface = m_system.GetPowerPC().GetDebugInterface();
-  PatchInstructionDialog dialog(this, addr, debug_interface.ReadInstruction(guard, addr));
 
+  if (assemble)
+  {
+    AssembleInstructionDialog dialog(this, addr, debug_interface.ReadInstruction(guard, addr));
     SetQWidgetWindowDecorations(&dialog);
     if (dialog.exec() == QDialog::Accepted)
     {
       debug_interface.SetPatch(guard, addr, dialog.GetCode());
       Update(&guard);
     }
+  }
+  else
+  {
+    PatchInstructionDialog dialog(this, addr, debug_interface.ReadInstruction(guard, addr));
+    SetQWidgetWindowDecorations(&dialog);
+    if (dialog.exec() == QDialog::Accepted)
+    {
+      debug_interface.SetPatch(guard, addr, dialog.GetCode());
+      Update(&guard);
+    }
+  }
 }
 
 void CodeViewWidget::OnRestoreInstruction()

Source/Core/DolphinQt/Debugger/CodeViewWidget.h

@@ -95,6 +95,8 @@ private:
   void OnInsertBLR();
   void OnInsertNOP();
   void OnReplaceInstruction();
+  void OnAssembleInstruction();
+  void DoPatchInstruction(bool assemble);
   void OnRestoreInstruction();
 
   void CalculateBranchIndentation();

Source/Core/DolphinQt/Debugger/GekkoSyntaxHighlight.cpp

@@ -0,0 +1,261 @@
+// Copyright 2023 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "DolphinQt/Debugger/GekkoSyntaxHighlight.h"
+
+#include "Common/Assembler/GekkoParser.h"
+
+#include <QLabel>
+#include <QPalette>
+
+namespace
+{
+using namespace Common::GekkoAssembler;
+using namespace Common::GekkoAssembler::detail;
+
+class HighlightParsePlugin : public ParsePlugin
+{
+public:
+  virtual ~HighlightParsePlugin() = default;
+
+  std::vector<std::pair<int, int>>&& MoveParens() { return std::move(m_matched_parens); }
+  std::vector<std::tuple<int, int, HighlightFormat>>&& MoveFormatting()
+  {
+    return std::move(m_formatting);
+  }
+
+  void OnDirectivePre(GekkoDirective) override { HighlightCurToken(HighlightFormat::Directive); }
+
+  void OnInstructionPre(const ParseInfo&, bool) override
+  {
+    HighlightCurToken(HighlightFormat::Mnemonic);
+  }
+
+  void OnTerminal(Terminal type, const AssemblerToken& val) override
+  {
+    switch (type)
+    {
+    case Terminal::Id:
+      HighlightCurToken(HighlightFormat::Symbol);
+      break;
+
+    case Terminal::Hex:
+    case Terminal::Dec:
+    case Terminal::Oct:
+    case Terminal::Bin:
+    case Terminal::Flt:
+      HighlightCurToken(HighlightFormat::Immediate);
+      break;
+
+    case Terminal::GPR:
+      HighlightCurToken(HighlightFormat::GPR);
+      break;
+
+    case Terminal::FPR:
+      HighlightCurToken(HighlightFormat::GPR);
+      break;
+
+    case Terminal::SPR:
+      HighlightCurToken(HighlightFormat::SPR);
+      break;
+
+    case Terminal::CRField:
+      HighlightCurToken(HighlightFormat::CRField);
+      break;
+
+    case Terminal::Lt:
+    case Terminal::Gt:
+    case Terminal::Eq:
+    case Terminal::So:
+      HighlightCurToken(HighlightFormat::CRFlag);
+      break;
+
+    case Terminal::Str:
+      HighlightCurToken(HighlightFormat::Str);
+      break;
+
+    default:
+      break;
+    }
+  }
+
+  void OnHiaddr(std::string_view) override
+  {
+    HighlightCurToken(HighlightFormat::Symbol);
+    auto&& [ha_pos, ha_tok] = m_owner->lexer.LookaheadTagRef(2);
+    m_formatting.emplace_back(static_cast<int>(ha_pos.col),
+                              static_cast<int>(ha_tok.token_val.length()), HighlightFormat::HaLa);
+  }
+
+  void OnLoaddr(std::string_view id) override { OnHiaddr(id); }
+
+  void OnOpenParen(ParenType type) override
+  {
+    m_paren_stack.push_back(static_cast<int>(m_owner->lexer.ColNumber()));
+  }
+
+  void OnCloseParen(ParenType type) override
+  {
+    if (m_paren_stack.empty())
+    {
+      return;
+    }
+
+    m_matched_parens.emplace_back(m_paren_stack.back(),
+                                  static_cast<int>(m_owner->lexer.ColNumber()));
+    m_paren_stack.pop_back();
+  }
+
+  void OnError() override
+  {
+    m_formatting.emplace_back(static_cast<int>(m_owner->error->col),
+                              static_cast<int>(m_owner->error->len), HighlightFormat::Error);
+  }
+
+  void OnLabelDecl(std::string_view name) override
+  {
+    const int len = static_cast<int>(m_owner->lexer.LookaheadRef().token_val.length());
+    const int off = static_cast<int>(m_owner->lexer.ColNumber());
+    m_formatting.emplace_back(len, off, HighlightFormat::Symbol);
+  }
+
+  void OnVarDecl(std::string_view name) override { OnLabelDecl(name); }
+
+private:
+  std::vector<int> m_paren_stack;
+  std::vector<std::pair<int, int>> m_matched_parens;
+  std::vector<std::tuple<int, int, HighlightFormat>> m_formatting;
+
+  void HighlightCurToken(HighlightFormat format)
+  {
+    const int len = static_cast<int>(m_owner->lexer.LookaheadRef().token_val.length());
+    const int off = static_cast<int>(m_owner->lexer.ColNumber());
+    m_formatting.emplace_back(off, len, format);
+  }
+};
+}  // namespace
+
+void GekkoSyntaxHighlight::highlightBlock(const QString& text)
+{
+  BlockInfo* info = static_cast<BlockInfo*>(currentBlockUserData());
+  if (info == nullptr)
+  {
+    info = new BlockInfo;
+    setCurrentBlockUserData(info);
+  }
+
+  qsizetype comment_idx = text.indexOf(QLatin1Char('#'));
+  if (comment_idx != -1)
+  {
+    HighlightSubstr(comment_idx, text.length() - comment_idx, HighlightFormat::Comment);
+  }
+
+  if (m_mode == 0)
+  {
+    HighlightParsePlugin plugin;
+    ParseWithPlugin(&plugin, text.toStdString());
+
+    info->block_format = plugin.MoveFormatting();
+    info->parens = plugin.MoveParens();
+    info->error = std::move(plugin.Error());
+    info->error_at_eol = info->error && info->error->len == 0;
+  }
+  else if (m_mode == 1)
+  {
+    auto paren_it = std::find_if(info->parens.begin(), info->parens.end(),
+                                 [this](const std::pair<int, int>& p) {
+                                   return p.first == m_cursor_loc || p.second == m_cursor_loc;
+                                 });
+    if (paren_it != info->parens.end())
+    {
+      HighlightSubstr(paren_it->first, 1, HighlightFormat::Paren);
+      HighlightSubstr(paren_it->second, 1, HighlightFormat::Paren);
+    }
+  }
+
+  for (auto&& [off, len, format] : info->block_format)
+  {
+    HighlightSubstr(off, len, format);
+  }
+}
+
+GekkoSyntaxHighlight::GekkoSyntaxHighlight(QTextDocument* document, QTextCharFormat base_format,
+                                           bool dark_scheme)
+    : QSyntaxHighlighter(document), m_base_format(base_format)
+{
+  QPalette base_scheme;
+  m_theme_idx = dark_scheme ? 1 : 0;
+}
+
+void GekkoSyntaxHighlight::HighlightSubstr(int start, int len, HighlightFormat format)
+{
+  QTextCharFormat hl_format = m_base_format;
+  const QColor DIRECTIVE_COLOR[2] = {QColor(0x9d, 0x00, 0x06),
+                                     QColor(0xfb, 0x49, 0x34)};  // Gruvbox darkred
+  const QColor MNEMONIC_COLOR[2] = {QColor(0x79, 0x74, 0x0e),
+                                    QColor(0xb8, 0xbb, 0x26)};  // Gruvbox darkgreen
+  const QColor IMM_COLOR[2] = {QColor(0xb5, 0x76, 0x14),
+                               QColor(0xfa, 0xbd, 0x2f)};  // Gruvbox darkyellow
+  const QColor BUILTIN_COLOR[2] = {QColor(0x07, 0x66, 0x78),
+                                   QColor(0x83, 0xa5, 0x98)};  // Gruvbox darkblue
+  const QColor HA_LA_COLOR[2] = {QColor(0xaf, 0x3a, 0x03),
+                                 QColor(0xfe, 0x80, 0x19)};  // Gruvbox darkorange
+  const QColor HOVER_BG_COLOR[2] = {QColor(0xd5, 0xc4, 0xa1),
+                                    QColor(0x50, 0x49, 0x45)};  // Gruvbox bg2
+  const QColor STRING_COLOR[2] = {QColor(0x98, 0x97, 0x1a),
+                                  QColor(0x98, 0x97, 0x1a)};  // Gruvbox green
+  const QColor COMMENT_COLOR[2] = {QColor(0x68, 0x9d, 0x6a),
+                                   QColor(0x68, 0x9d, 0x6a)};  // Gruvbox aqua
+
+  switch (format)
+  {
+  case HighlightFormat::Directive:
+    hl_format.setForeground(DIRECTIVE_COLOR[m_theme_idx]);
+    break;
+  case HighlightFormat::Mnemonic:
+    hl_format.setForeground(MNEMONIC_COLOR[m_theme_idx]);
+    break;
+  case HighlightFormat::Symbol:
+    break;
+  case HighlightFormat::Immediate:
+    hl_format.setForeground(IMM_COLOR[m_theme_idx]);
+    break;
+  case HighlightFormat::GPR:
+    hl_format.setForeground(BUILTIN_COLOR[m_theme_idx]);
+    break;
+  case HighlightFormat::FPR:
+    hl_format.setForeground(BUILTIN_COLOR[m_theme_idx]);
+    break;
+  case HighlightFormat::SPR:
+    hl_format.setForeground(BUILTIN_COLOR[m_theme_idx]);
+    break;
+  case HighlightFormat::CRField:
+    hl_format.setForeground(BUILTIN_COLOR[m_theme_idx]);
+    break;
+  case HighlightFormat::CRFlag:
+    hl_format.setForeground(BUILTIN_COLOR[m_theme_idx]);
+    break;
+  case HighlightFormat::Str:
+    hl_format.setForeground(STRING_COLOR[m_theme_idx]);
+    break;
+  case HighlightFormat::HaLa:
+    hl_format.setForeground(HA_LA_COLOR[m_theme_idx]);
+    break;
+  case HighlightFormat::Paren:
+    hl_format.setBackground(HOVER_BG_COLOR[m_theme_idx]);
+    break;
+  case HighlightFormat::Default:
+    hl_format.clearForeground();
+    hl_format.clearBackground();
+    break;
+  case HighlightFormat::Comment:
+    hl_format.setForeground(COMMENT_COLOR[m_theme_idx]);
+    break;
+  case HighlightFormat::Error:
+    hl_format.setUnderlineColor(Qt::red);
+    hl_format.setUnderlineStyle(QTextCharFormat::WaveUnderline);
+    break;
+  }
+
+  setFormat(start, len, hl_format);
+}

Source/Core/DolphinQt/Debugger/GekkoSyntaxHighlight.h

@@ -0,0 +1,60 @@
+// Copyright 2023 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <QSyntaxHighlighter>
+#include <QTextCharFormat>
+
+#include <optional>
+
+#include "Common/Assembler/AssemblerShared.h"
+
+enum class HighlightFormat
+{
+  Directive,
+  Mnemonic,
+  Symbol,
+  Immediate,
+  GPR,
+  FPR,
+  SPR,
+  CRField,
+  CRFlag,
+  Str,
+  HaLa,
+  Paren,
+  Default,
+  Comment,
+  Error,
+};
+
+struct BlockInfo : public QTextBlockUserData
+{
+  std::vector<std::tuple<int, int, HighlightFormat>> block_format;
+  std::vector<std::pair<int, int>> parens;
+  std::optional<Common::GekkoAssembler::AssemblerError> error;
+  bool error_at_eol = false;
+};
+
+class GekkoSyntaxHighlight : public QSyntaxHighlighter
+{
+  Q_OBJECT;
+
+public:
+  explicit GekkoSyntaxHighlight(QTextDocument* document, QTextCharFormat base_format,
+                                bool dark_scheme);
+
+  void HighlightSubstr(int start, int len, HighlightFormat format);
+  void SetMode(int mode) { m_mode = mode; }
+  void SetCursorLoc(int loc) { m_cursor_loc = loc; }
+
+protected:
+  void highlightBlock(const QString& line) override;
+
+private:
+  int m_mode = 0;
+  int m_cursor_loc = 0;
+  QTextCharFormat m_base_format;
+  int m_theme_idx = 0;
+};

Source/Core/DolphinQt/GameList/GameList.cpp

@@ -123,8 +123,10 @@ GameList::GameList(QWidget* parent) : QStackedWidget(parent), m_model(this)
   m_prefer_list = Settings::Instance().GetPreferredView();
   ConsiderViewChange();
 
-  const auto* zoom_in = new QShortcut(QKeySequence::ZoomIn, this);
-  const auto* zoom_out = new QShortcut(QKeySequence::ZoomOut, this);
+  auto* zoom_in = new QShortcut(QKeySequence::ZoomIn, this);
+  auto* zoom_out = new QShortcut(QKeySequence::ZoomOut, this);
+  zoom_in->setContext(Qt::WidgetWithChildrenShortcut);
+  zoom_out->setContext(Qt::WidgetWithChildrenShortcut);
 
   connect(zoom_in, &QShortcut::activated, this, &GameList::ZoomIn);
   connect(zoom_out, &QShortcut::activated, this, &GameList::ZoomOut);

Source/Core/DolphinQt/MainWindow.cpp

@@ -82,6 +82,7 @@
 #include "DolphinQt/Config/LogWidget.h"
 #include "DolphinQt/Config/Mapping/MappingWindow.h"
 #include "DolphinQt/Config/SettingsWindow.h"
+#include "DolphinQt/Debugger/AssemblerWidget.h"
 #include "DolphinQt/Debugger/BreakpointWidget.h"
 #include "DolphinQt/Debugger/CodeViewWidget.h"
 #include "DolphinQt/Debugger/CodeWidget.h"
@@ -449,6 +450,7 @@ void MainWindow::CreateComponents()
   m_breakpoint_widget = new BreakpointWidget(this);
   m_code_widget = new CodeWidget(this);
   m_cheats_manager = new CheatsManager(this);
+  m_assembler_widget = new AssemblerWidget(this);
 
   const auto request_watch = [this](QString name, u32 addr) {
     m_watch_widget->AddWatch(name, addr);
@@ -740,6 +742,7 @@ void MainWindow::ConnectStack()
   addDockWidget(Qt::LeftDockWidgetArea, m_memory_widget);
   addDockWidget(Qt::LeftDockWidgetArea, m_network_widget);
   addDockWidget(Qt::LeftDockWidgetArea, m_jit_widget);
+  addDockWidget(Qt::LeftDockWidgetArea, m_assembler_widget);
 
   tabifyDockWidget(m_log_widget, m_log_config_widget);
   tabifyDockWidget(m_log_widget, m_code_widget);
@@ -750,6 +753,7 @@ void MainWindow::ConnectStack()
   tabifyDockWidget(m_log_widget, m_memory_widget);
   tabifyDockWidget(m_log_widget, m_network_widget);
   tabifyDockWidget(m_log_widget, m_jit_widget);
+  tabifyDockWidget(m_log_widget, m_assembler_widget);
 }
 
 void MainWindow::RefreshGameList()
@@ -872,7 +876,16 @@ void MainWindow::OnStopComplete()
   SetFullScreenResolution(false);
 
   if (m_exit_requested || Settings::Instance().IsBatchModeEnabled())
+  {
+    if (m_assembler_widget->ApplicationCloseRequest())
+    {
       QGuiApplication::exit(0);
+    }
+    else
+    {
+      m_exit_requested = false;
+    }
+  }
 
   // If the current emulation prevented the booting of another, do that now
   if (m_pending_boot != nullptr)

Source/Core/DolphinQt/MainWindow.h

@@ -18,6 +18,7 @@ class QStackedWidget;
 class QString;
 
 class AchievementsWindow;
+class AssemblerWidget;
 class BreakpointWidget;
 struct BootParameters;
 class CheatsManager;
@@ -259,6 +260,7 @@ private:
   AchievementsWindow* m_achievements_window = nullptr;
 #endif  // USE_RETRO_ACHIEVEMENTS
 
+  AssemblerWidget* m_assembler_widget;
   BreakpointWidget* m_breakpoint_widget;
   CodeWidget* m_code_widget;
   JITWidget* m_jit_widget;

Source/Core/DolphinQt/MenuBar.cpp

@@ -494,6 +494,14 @@ void MenuBar::AddViewMenu()
   connect(m_show_jit, &QAction::toggled, &Settings::Instance(), &Settings::SetJITVisible);
   connect(&Settings::Instance(), &Settings::JITVisibilityChanged, m_show_jit, &QAction::setChecked);
 
+  m_show_assembler = view_menu->addAction(tr("&Assembler"));
+  m_show_assembler->setCheckable(true);
+  m_show_assembler->setChecked(Settings::Instance().IsAssemblerVisible());
+  connect(m_show_assembler, &QAction::toggled, &Settings::Instance(),
+          &Settings::SetAssemblerVisible);
+  connect(&Settings::Instance(), &Settings::AssemblerVisibilityChanged, m_show_assembler,
+          &QAction::setChecked);
+
   view_menu->addSeparator();
 
   AddGameListTypeSection(view_menu);

Source/Core/DolphinQt/MenuBar.h

@@ -253,6 +253,7 @@ private:
   QAction* m_show_memory;
   QAction* m_show_network;
   QAction* m_show_jit;
+  QAction* m_show_assembler;
   QMenu* m_cols_menu;
 
   // JIT

Source/Core/DolphinQt/Settings.cpp

@@ -693,6 +693,20 @@ bool Settings::IsJITVisible() const
   return QSettings().value(QStringLiteral("debugger/showjit")).toBool();
 }
 
+void Settings::SetAssemblerVisible(bool enabled)
+{
+  if (IsAssemblerVisible() == enabled)
+    return;
+  QSettings().setValue(QStringLiteral("debugger/showassembler"), enabled);
+
+  emit AssemblerVisibilityChanged(enabled);
+}
+
+bool Settings::IsAssemblerVisible() const
+{
+  return QSettings().value(QStringLiteral("debugger/showassembler")).toBool();
+}
+
 void Settings::RefreshWidgetVisibility()
 {
   emit DebugModeToggled(IsDebugModeEnabled());

Source/Core/DolphinQt/Settings.h

@@ -166,6 +166,8 @@ public:
   bool IsNetworkVisible() const;
   void SetJITVisible(bool enabled);
   bool IsJITVisible() const;
+  void SetAssemblerVisible(bool enabled);
+  bool IsAssemblerVisible() const;
   QFont GetDebugFont() const;
   void SetDebugFont(QFont font);
 
@@ -213,6 +215,7 @@ signals:
   void MemoryVisibilityChanged(bool visible);
   void NetworkVisibilityChanged(bool visible);
   void JITVisibilityChanged(bool visible);
+  void AssemblerVisibilityChanged(bool visible);
   void DebugModeToggled(bool enabled);
   void DebugFontChanged(QFont font);
   void AutoUpdateTrackChanged(const QString& mode);

Source/Core/UICommon/UICommon.cpp

@@ -266,6 +266,7 @@ void CreateDirectories()
   File::CreateFullPath(File::GetUserPath(D_SHADERS_IDX));
   File::CreateFullPath(File::GetUserPath(D_SHADERS_IDX) + ANAGLYPH_DIR DIR_SEP);
   File::CreateFullPath(File::GetUserPath(D_STATESAVES_IDX));
+  File::CreateFullPath(File::GetUserPath(D_ASM_ROOT_IDX));
 #ifndef ANDROID
   File::CreateFullPath(File::GetUserPath(D_THEMES_IDX));
   File::CreateFullPath(File::GetUserPath(D_STYLES_IDX));