From 27b751ec46e59166867cedbf6da3ee19453671bd Mon Sep 17 00:00:00 2001
From: Gabe Black <gblack@eecs.umich.edu>
Date: Fri, 27 Feb 2009 09:26:09 -0800
Subject: X86: Don't treat the REX prefixes as prefixes in 32 bit modes. These
 are inc/dec instructions.

---
 src/arch/x86/predecoder.cc | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

(limited to 'src/arch/x86/predecoder.cc')

diff --git a/src/arch/x86/predecoder.cc b/src/arch/x86/predecoder.cc
index 9d60089e3..620ab89ea 100644
--- a/src/arch/x86/predecoder.cc
+++ b/src/arch/x86/predecoder.cc
@@ -136,7 +136,10 @@ namespace X86ISA
     {
         uint8_t prefix = Prefixes[nextByte];
         State nextState = PrefixState;
-        if(prefix)
+        // REX prefixes are only recognized in 64 bit mode.
+        if (prefix == RexPrefix && emi.mode.submode != SixtyFourBitMode)
+            prefix = 0;
+        if (prefix)
             consumeByte();
         switch(prefix)
         {
-- 
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