From b7c3f91643535b760a71de5b1faaae2b91ac7af2 Mon Sep 17 00:00:00 2001
From: Sintendo <3380580+Sintendo@users.noreply.github.com>
Date: Sat, 1 Feb 2025 21:11:23 +0100
Subject: [PATCH] JitArm64_Integer: cmpl - Subtract 12-bit constant

You can encode a 12-bit immediate in a SUB instruction on ARM64. We can
exploit this to avoid materializing the immediate.

This approach saves an instruction if it does not need to be
materialized in a register afterwards. Otherwise, we just materialize
it later and the total number of instructions stays the same.

Before:
0x5280003a   mov    w26, #0x1                 ; =1
0xcb1a033b   sub    x27, x25, x26

After:
0xd100073b   sub    x27, x25, #0x1
---
 Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp b/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
index 518922343d..ef44a72efd 100644
--- a/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
+++ b/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
@@ -728,9 +728,13 @@ void JitArm64::cmpl(UGeckoInstruction inst)
   {
     NEG(CR, EncodeRegTo64(gpr.R(b)));
   }
-  else if (gpr.IsImm(b) && !gpr.GetImm(b))
+  else if (gpr.IsImm(b) && (gpr.GetImm(b) & 0xFFF) == gpr.GetImm(b))
   {
-    MOV(EncodeRegTo32(CR), gpr.R(a));
+    const u32 imm = gpr.GetImm(b);
+    if (imm == 0)
+      MOV(EncodeRegTo32(CR), gpr.R(a));
+    else
+      SUB(CR, EncodeRegTo64(gpr.R(a)), imm);
   }
   else
   {