From fb5e522fbc0750c838ef6a926b11c5d870826183 Mon Sep 17 00:00:00 2001
From: Mike Pall <mike>
Date: Sun, 20 May 2018 12:40:33 +0200
Subject: [PATCH] x86/x64: Check for jcc when using xor r,r in emit_loadi().

Thanks to Peter Cawley.
---
 src/lj_emit_x86.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/lj_emit_x86.h b/src/lj_emit_x86.h
index bcceb93e..9c371a95 100644
--- a/src/lj_emit_x86.h
+++ b/src/lj_emit_x86.h
@@ -268,10 +268,12 @@ static void emit_movmroi(ASMState *as, Reg base, int32_t ofs, int32_t i)
 /* mov r, i / xor r, r */
 static void emit_loadi(ASMState *as, Reg r, int32_t i)
 {
-  /* XOR r,r is shorter, but modifies the flags. This is bad for HIOP. */
+  /* XOR r,r is shorter, but modifies the flags. This is bad for HIOP/jcc. */
   if (i == 0 && !(LJ_32 && (IR(as->curins)->o == IR_HIOP ||
 			    (as->curins+1 < as->T->nins &&
-			     IR(as->curins+1)->o == IR_HIOP)))) {
+			     IR(as->curins+1)->o == IR_HIOP))) &&
+		!((*as->mcp == 0x0f && (as->mcp[1] & 0xf0) == XI_JCCn) ||
+		  (*as->mcp & 0xf0) == XI_JCCs)) {
     emit_rr(as, XO_ARITH(XOg_XOR), r, r);
   } else {
     MCode *p = as->mcp;