Fix assembler sequence for cmppd

REX prefix should be after mandatory prefix and before opcode.

Change-Id: I9829384d7d617d3be203026ae84ffa30aaef6d2e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1726983
Commit-Queue: Bill Budge <bbudge@chromium.org>
Auto-Submit: Zhi An Ng <zhin@chromium.org>
Reviewed-by: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62997}

src/codegen/x64/assembler-x64.cc

@@ -3527,8 +3527,8 @@ void Assembler::cmpps(XMMRegister dst, Operand src, int8_t cmp) {
 
 void Assembler::cmppd(XMMRegister dst, XMMRegister src, int8_t cmp) {
   EnsureSpace ensure_space(this);
-  emit_optional_rex_32(dst, src);
   emit(0x66);
+  emit_optional_rex_32(dst, src);
   emit(0x0F);
   emit(0xC2);
   emit_sse_operand(dst, src);
@@ -3537,8 +3537,8 @@ void Assembler::cmppd(XMMRegister dst, XMMRegister src, int8_t cmp) {
 
 void Assembler::cmppd(XMMRegister dst, Operand src, int8_t cmp) {
   EnsureSpace ensure_space(this);
-  emit_optional_rex_32(dst, src);
   emit(0x66);
+  emit_optional_rex_32(dst, src);
   emit(0x0F);
   emit(0xC2);
   emit_sse_operand(dst, src);