[ia32/x64] Smaller instruction to check NaN

src/x64/macro-assembler-x64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 3041 matching lines @@
 
   CompareMap(obj, map);
   j(not_equal, fail);
 }
 
 
 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);
 }
 
 
 void MacroAssembler::ClampDoubleToUint8(XMMRegister input_reg,
                                         XMMRegister temp_xmm_reg,
                                         Register result_reg) {
   Label done;
   Label conv_failure;
   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);
   ucomisd(input_reg, temp_xmm_reg);
   j(below, &done, Label::kNear);
   Set(result_reg, 255);
   bind(&done);
 }
 
 
@@ skipping 14 matching lines @@
   DoubleToIStub stub(input_reg, result_reg, offset, true);
   call(stub.GetCode(isolate()), RelocInfo::CODE_TARGET);
 }
 
 
 void MacroAssembler::TruncateHeapNumberToI(Register result_reg,
                                            Register input_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)) {
     subq(rsp, Immediate(kDoubleSize));
     movsd(MemOperand(rsp, 0), xmm0);
     SlowTruncateToI(result_reg, rsp, 0);
     addq(rsp, Immediate(kDoubleSize));
   } else {
     SlowTruncateToI(result_reg, input_reg);
   }
 
   bind(&done);
 }
 
 
 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);
   SlowTruncateToI(result_reg, rsp, 0);
   addq(rsp, Immediate(kDoubleSize));
 
   bind(&done);
 }
 
 
@@ skipping 1835 matching lines @@
   imull(dividend);
   if (divisor > 0 && ms.multiplier() < 0) addl(rdx, dividend);
   if (divisor < 0 && ms.multiplier() > 0) subl(rdx, dividend);
   if (ms.shift() > 0) sarl(rdx, Immediate(ms.shift()));
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64