X64: Change strategy for spilling to match ia32. It's just better.

src/x64/macro-assembler-x64.cc

Index: src/x64/macro-assembler-x64.cc
diff --git a/src/x64/macro-assembler-x64.cc b/src/x64/macro-assembler-x64.cc
index 3e5771728cd6cd5838f325467a20797e529c180f..24bac7d3693c6b5d22dd98a31f0f7e25d934cee5 100644
--- a/src/x64/macro-assembler-x64.cc
+++ b/src/x64/macro-assembler-x64.cc
@@ -456,13 +456,8 @@ void MacroAssembler::Set(Register dst, int64_t x) {
 
 
 void MacroAssembler::Set(const Operand& dst, int64_t x) {
-  if (x == 0) {
-    xor_(kScratchRegister, kScratchRegister);
-    movq(dst, kScratchRegister);
-  } else if (is_int32(x)) {
+  if (is_int32(x)) {
     movq(dst, Immediate(static_cast<int32_t>(x)));
-  } else if (is_uint32(x)) {
-    movl(dst, Immediate(static_cast<uint32_t>(x)));
   } else {
     movq(kScratchRegister, x, RelocInfo::NONE);
     movq(dst, kScratchRegister);