From 18dd3f69f15f8659f74a7b69627db924b9d169df Mon Sep 17 00:00:00 2001
From: Sintendo <3380580+Sintendo@users.noreply.github.com>
Date: Sat, 28 Dec 2024 18:15:44 +0100
Subject: [PATCH] JitArm64_Integer: subfex - Optimize InPPCState case for 0

When the immediate is zero, we can load the carry flag from memory
directly to the destination register.

Before:
0x394bd3b8   ldrb   w24, [x29, #0x2f4]
0x2a1803f9   mov    w25, w24

After:
0x394bd3b9   ldrb   w25, [x29, #0x2f4]
---
 .../Core/PowerPC/JitArm64/JitArm64_Integer.cpp     | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp b/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
index 41ad4290d0..3b6aef8788 100644
--- a/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
+++ b/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
@@ -1219,6 +1219,7 @@ void JitArm64::subfex(UGeckoInstruction inst)
     const u32 i = gpr.GetImm(a);
     const u32 j = mex ? -1 : gpr.GetImm(b);
     const u32 imm = ~i + j;
+    const bool is_zero = imm == 0;
     const bool is_all_ones = imm == 0xFFFFFFFF;
 
     switch (js.carryFlag)
@@ -1227,9 +1228,16 @@ void JitArm64::subfex(UGeckoInstruction inst)
     {
       gpr.BindToRegister(d, false);
       ARM64Reg RD = gpr.R(d);
-      auto WA = gpr.GetScopedReg();
-      LDRB(IndexType::Unsigned, WA, PPC_REG, PPCSTATE_OFF(xer_ca));
-      ADDI2R(RD, WA, imm, RD);
+      if (is_zero)
+      {
+        LDRB(IndexType::Unsigned, RD, PPC_REG, PPCSTATE_OFF(xer_ca));
+      }
+      else
+      {
+        auto WA = gpr.GetScopedReg();
+        LDRB(IndexType::Unsigned, WA, PPC_REG, PPCSTATE_OFF(xer_ca));
+        ADDI2R(RD, WA, imm, RD);
+      }
       break;
     }
     case CarryFlag::InHostCarry: