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-rw-r--r--src/arch/x86/predecoder.cc5
1 files changed, 4 insertions, 1 deletions
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)
{