[ia32/x64] Smaller instruction to check NaN

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 3191199271613443a6dfe3ebdff826e22c28da5c..910d0b3f2d84c1512c56aff6ac0361450b4c2ad3 100644
--- a/src/x64/macro-assembler-x64.cc
+++ b/src/x64/macro-assembler-x64.cc
@@ -3059,8 +3059,8 @@ void MacroAssembler::ClampUint8(Register reg) {
   Label done;
   testl(reg, Immediate(0xFFFFFF00));
   j(zero, &done, Label::kNear);
-  setcc(negative, reg);  // 1 if negative, 0 if positive.
-  decb(reg);  // 0 if negative, 255 if positive.
+  sarl(reg, Immediate(31));
+  notl(reg);
   bind(&done);
 }
 
@@ -3073,13 +3073,12 @@ void MacroAssembler::ClampDoubleToUint8(XMMRegister input_reg,
   xorps(temp_xmm_reg, temp_xmm_reg);
   cvtsd2si(result_reg, input_reg);
   testl(result_reg, Immediate(0xFFFFFF00));
-  j(zero, &done, Label::kNear);
-  cmpl(result_reg, Immediate(0x80000000));
-  j(equal, &conv_failure, Label::kNear);
-  movl(result_reg, Immediate(0));
-  setcc(above, result_reg);
-  subl(result_reg, Immediate(1));
-  andl(result_reg, Immediate(255));
+  j(below_equal, &done, Label::kNear);

[Jakob Kummerow, 2014/03/17 18:06:46]

This change is confusing. "zero" should have the same effect as "below_equal" in
this case, and is much more readable. Or am I missing something?

[Weiliang, 2014/03/18 06:06:40]

Oh, this is a stale change which I forget to change back. Sorry for that.
On 2014/03/17 18:06:46, Jakob wrote:

[Weiliang, 2014/03/18 06:06:40]

Done.

+  cmpl(result_reg, Immediate(1));
+  j(overflow, &conv_failure, Label::kNear);
+  sarl(result_reg, Immediate(31));
+  notl(result_reg);
+  movzxbl(result_reg, result_reg);
   jmp(&done, Label::kNear);
   bind(&conv_failure);
   Set(result_reg, 0);
@@ -3114,9 +3113,8 @@ void MacroAssembler::TruncateHeapNumberToI(Register result_reg,
   Label done;
   movsd(xmm0, FieldOperand(input_reg, HeapNumber::kValueOffset));
   cvttsd2siq(result_reg, xmm0);
-  Set(kScratchRegister, V8_UINT64_C(0x8000000000000000));
-  cmpq(result_reg, kScratchRegister);
-  j(not_equal, &done, Label::kNear);
+  cmpq(result_reg, Immediate(1));
+  j(no_overflow, &done, Label::kNear);
 
   // Slow case.
   if (input_reg.is(result_reg)) {
@@ -3136,9 +3134,8 @@ void MacroAssembler::TruncateDoubleToI(Register result_reg,
                                        XMMRegister input_reg) {
   Label done;
   cvttsd2siq(result_reg, input_reg);
-  movq(kScratchRegister, V8_INT64_C(0x8000000000000000));
-  cmpq(result_reg, kScratchRegister);
-  j(not_equal, &done, Label::kNear);
+  cmpq(result_reg, Immediate(1));
+  j(no_overflow, &done, Label::kNear);
 
   subq(rsp, Immediate(kDoubleSize));
   movsd(MemOperand(rsp, 0), input_reg);