[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..43edf235dd918a40a87456c1e7c62870a4c3e666 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);  // safe not to zero extension
   bind(&done);
 }
 
@@ -3074,18 +3074,16 @@ void MacroAssembler::ClampDoubleToUint8(XMMRegister input_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));
+  cmpl(result_reg, Immediate(1));
+  j(overflow, &conv_failure, Label::kNear);
+  sarl(result_reg, Immediate(31));
+  notl(result_reg);  // safe not to zero extension
   jmp(&done, Label::kNear);
   bind(&conv_failure);
-  Set(result_reg, 0);
+  sarl(result_reg, Immediate(31));
   ucomisd(input_reg, temp_xmm_reg);
-  j(below, &done, Label::kNear);
-  Set(result_reg, 255);
+  j(above_equal, &done, Label::kNear);
+  Set(result_reg, 0);
   bind(&done);
 }
 
@@ -3114,9 +3112,8 @@ 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 +3133,8 @@ 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);