ART: Fixes an issue with REX prefix for instructions with no ModRM byte

There are instructions (such as push, pop, mov) in the x86 ISA
that encode first operands in their opcodes (opcode + reg).
In order to enable an extended 64bit registers (R9-R15) a special
prefix REX.B should be emitted before such instructions.

This patch fixes the issue when REX.R prefix was emitted before
instructions with no MorRM byte. So, the REX-prefix was simply
ignored by CPU for those instructions whose operands are encoded
in their opcodes.

This patch makes the jni_compiler_test passed with JNI compiler
enabled for x86_64 target.

Change-Id: Ib84da1cf9f8ff96bd7afd4e0fc53078f3231f8ec
Signed-off-by: Vladimir Kostyukov <vladimir.kostyukov@intel.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/disassembler/disassembler_x86.cc b/disassembler/disassembler_x86.cc
index 68e77d44e4..1b96a2bf01 100644
--- a/disassembler/disassembler_x86.cc
+++ b/disassembler/disassembler_x86.cc
@@ -735,7 +735,7 @@ DISASSEMBLER_ENTRY(cmp,
   std::ostringstream args;
   if (reg_in_opcode) {
     DCHECK(!has_modrm);
-    DumpReg(args, rex, *instr & 0x7, false, prefix[2], GPR);
+    DumpBaseReg(args, rex, *instr & 0x7);
   }
   instr++;
   uint32_t address_bits = 0;