From 77bb01d3843e02b614b486ddef7e0849703b325a Mon Sep 17 00:00:00 2001
From: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Date: Thu, 22 May 2025 13:53:31 -0400
Subject: [PATCH] OpcodeDispatcher: don't generate pointless Xor for AF

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
---
 FEXCore/Source/Interface/Core/OpcodeDispatcher/Flags.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/FEXCore/Source/Interface/Core/OpcodeDispatcher/Flags.cpp b/FEXCore/Source/Interface/Core/OpcodeDispatcher/Flags.cpp
index b66827331..2351455df 100644
--- a/FEXCore/Source/Interface/Core/OpcodeDispatcher/Flags.cpp
+++ b/FEXCore/Source/Interface/Core/OpcodeDispatcher/Flags.cpp
@@ -247,7 +247,7 @@ void OpDispatchBuilder::CalculateAF(Ref Src1, Ref Src2) {
   // We store the XOR of the arguments. At read time, we XOR with the
   // appropriate bit of the result (available as the PF flag) and extract the
   // appropriate bit. Again 64-bit to avoid masking.
-  Ref XorRes = _Xor(OpSize::i64Bit, Src1, Src2);
+  Ref XorRes = Src1 == Src2 ? _Constant(0) : _Xor(OpSize::i64Bit, Src1, Src2);
   SetRFLAG<FEXCore::X86State::RFLAG_AF_RAW_LOC>(XorRes);
 }