[x64] Fix REX prefix in shufps

BUG=

Review-Url: https://codereview.chromium.org/2652793004
Cr-Commit-Position: refs/heads/master@{#42673}

src/x64/assembler-x64.cc

@@ -3034,7 +3034,7 @@ void Assembler::movaps(XMMRegister dst, XMMRegister src) {
 void Assembler::shufps(XMMRegister dst, XMMRegister src, byte imm8) {
   DCHECK(is_uint8(imm8));
   EnsureSpace ensure_space(this);
-  emit_optional_rex_32(src, dst);
+  emit_optional_rex_32(dst, src);
   emit(0x0F);
   emit(0xC6);
   emit_sse_operand(dst, src);

test/cctest/test-disasm-x64.cc

@@ -386,6 +386,7 @@ TEST(DisasmX64) {
     __ cvtsd2ss(xmm0, xmm1);
     __ cvtsd2ss(xmm0, Operand(rbx, rcx, times_4, 10000));
     __ movaps(xmm0, xmm1);
+    __ shufps(xmm0, xmm9, 0x0);
 
     // logic operation
     __ andps(xmm0, xmm1);