From 45a3e35b0684d8f42e51f2c074e208658125b49e Mon Sep 17 00:00:00 2001
From: Sintendo <3380580+Sintendo@users.noreply.github.com>
Date: Wed, 6 Aug 2025 01:22:01 +0200
Subject: [PATCH] JitArm64_Integer: subfcx - Subtract 12-bit constant

Eliminate an instruction by encoding the constant in the subtraction.

Before:
0x5280037a   mov    w26, #0x1b                ; =27
0x6b1a02bb   subs   w27, w21, w26
0x93407f78   sxtw   x24, w27

After:
0x71006ebb   subs   w27, w21, #0x1b
0x93407f7a   sxtw   x26, w27
---
 Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp b/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
index 25a4ada478..7cf2305d5a 100644
--- a/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
+++ b/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
@@ -1443,6 +1443,14 @@ void JitArm64::subfcx(UGeckoInstruction inst)
     if (inst.Rc)
       ComputeRC0(gpr.R(d));
   }
+  else if (gpr.IsImm(a) && ((gpr.GetImm(a) & 0xFFF) == gpr.GetImm(a)))
+  {
+    gpr.BindToRegister(d, d == b);
+    CARRY_IF_NEEDED(SUB, SUBS, gpr.R(d), gpr.R(b), gpr.GetImm(a));
+    ComputeCarry();
+    if (inst.Rc)
+      ComputeRC0(gpr.R(d));
+  }
   else if (gpr.IsImm(b, 0))
   {
     gpr.BindToRegister(d, d == a);