Small improvement in x64 assembler

Review URL: https://chromiumcodereview.appspot.com/12177012
Patch from Zheng Z. Liu <zheng.z.liu@intel.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13605 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/x64/assembler-x64.cc

@@ -1505,13 +1505,12 @@ void Assembler::movq(Register dst, void* value, RelocInfo::Mode rmode) {
 void Assembler::movq(Register dst, int64_t value, RelocInfo::Mode rmode) {
   // Non-relocatable values might not need a 64-bit representation.
   if (RelocInfo::IsNone(rmode)) {
-    // Sadly, there is no zero or sign extending move for 8-bit immediates.
-    if (is_int32(value)) {
-      movq(dst, Immediate(static_cast<int32_t>(value)));
-      return;
-    } else if (is_uint32(value)) {
+    if (is_uint32(value)) {
       movl(dst, Immediate(static_cast<int32_t>(value)));
       return;
+    } else if (is_int32(value)) {
+      movq(dst, Immediate(static_cast<int32_t>(value)));
+      return;
     }
     // Value cannot be represented by 32 bits, so do a full 64 bit immediate
     // value.

src/x64/macro-assembler-x64.cc

@@ -2911,23 +2911,14 @@ void MacroAssembler::ClampDoubleToUint8(XMMRegister input_reg,
 }
 
 
-static double kUint32Bias =
-    static_cast<double>(static_cast<uint32_t>(0xFFFFFFFF)) + 1;
-
-
 void MacroAssembler::LoadUint32(XMMRegister dst,
                                 Register src,
                                 XMMRegister scratch) {
-  Label done;
-  cmpl(src, Immediate(0));
-  movq(kScratchRegister,
-       reinterpret_cast<int64_t>(&kUint32Bias),
-       RelocInfo::NONE64);
-  movsd(scratch, Operand(kScratchRegister, 0));
-  cvtlsi2sd(dst, src);
-  j(not_sign, &done, Label::kNear);
-  addsd(dst, scratch);
-  bind(&done);
+  if (FLAG_debug_code) {
+    cmpq(src, Immediate(0xffffffff));
+    Assert(below_equal, "input GPR is expected to have upper32 cleared");
+  }
+  cvtqsi2sd(dst, src);
 }