From 6a92a90bce95641bf676a8214d80d2224b65ba83 Mon Sep 17 00:00:00 2001
From: Sintendo <3380580+Sintendo@users.noreply.github.com>
Date: Wed, 6 Aug 2025 01:27:35 +0200
Subject: [PATCH] JitArm64_Integer: subfcx - Subtract shifted 12-bit constant

Eliminate an instruction by encoding the constant in the subtraction,
part two.

Before:
0x52900019   mov    w25, #0x8000              ; =32768
0x6b190359   subs   w25, w26, w25

After:
0x71402359   subs   w25, w26, #0x8, lsl #12   ; =0x8000
---
 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 7cf2305d5a..3cf722409a 100644
--- a/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
+++ b/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
@@ -1451,6 +1451,14 @@ void JitArm64::subfcx(UGeckoInstruction inst)
     if (inst.Rc)
       ComputeRC0(gpr.R(d));
   }
+  else if (gpr.IsImm(a) && ((gpr.GetImm(a) & 0xFFF000) == gpr.GetImm(a)))
+  {
+    gpr.BindToRegister(d, d == b);
+    CARRY_IF_NEEDED(SUB, SUBS, gpr.R(d), gpr.R(b), gpr.GetImm(a) >> 12, true);
+    ComputeCarry();
+    if (inst.Rc)
+      ComputeRC0(gpr.R(d));
+  }
   else if (gpr.IsImm(b, 0))
   {
     gpr.BindToRegister(d, d == a);