From 82f22cdfa1fbaeaac8cf608294c4dc730ee0f099 Mon Sep 17 00:00:00 2001
From: Bram Speeckaert <bram.speeckaert@gmail.com>
Date: Tue, 1 Nov 2022 12:00:16 +0100
Subject: [PATCH] JitArm64: cmp - Optimize a == -1 case

By explicitly handling this, we can avoid materializing -1 in a
register and generate more efficient code by taking advantage of -x ==
~x + 1.

Before:
0x12800015   mov    w21, #-0x1
0x93407eb9   sxtw   x25, w21
0x93407ef8   sxtw   x24, w23
0xcb180338   sub    x24, x25, x24

After:
0x2a3703f8   mvn    w24, w23
0x93407f18   sxtw   x24, w24
---
 Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp b/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
index 2166a1427d..6378c322e7 100644
--- a/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
+++ b/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
@@ -584,6 +584,11 @@ void JitArm64::cmp(UGeckoInstruction inst)
     NEG(EncodeRegTo32(CR), gpr.R(b));
     SXTW(CR, EncodeRegTo32(CR));
   }
+  else if (gpr.IsImm(a) && gpr.GetImm(a) == 0xFFFFFFFF)
+  {
+    MVN(EncodeRegTo32(CR), gpr.R(b));
+    SXTW(CR, EncodeRegTo32(CR));
+  }
   else if (gpr.IsImm(b) && !gpr.GetImm(b))
   {
     SXTW(CR, gpr.R(a));