[ia32/x64] Smaller instruction to check NaN

src/ia32/macro-assembler-ia32.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 196 matching lines @@
     bind(&done);
   }
 }
 
 
 void MacroAssembler::ClampDoubleToUint8(XMMRegister input_reg,
                                         XMMRegister scratch_reg,
                                         Register result_reg) {
   Label done;
   Label conv_failure;
-  pxor(scratch_reg, scratch_reg);
+  xorps(scratch_reg, scratch_reg);
   cvtsd2si(result_reg, input_reg);
   test(result_reg, Immediate(0xFFFFFF00));
   j(zero, &done, Label::kNear);
-  cmp(result_reg, Immediate(0x80000000));
-  j(equal, &conv_failure, Label::kNear);
-  mov(result_reg, Immediate(0));
-  setcc(above, result_reg);
-  sub(result_reg, Immediate(1));
-  and_(result_reg, Immediate(255));
+  cmp(result_reg, Immediate(0x1));
+  j(overflow, &conv_failure, Label::kNear);
+  sar(result_reg, 31);
+  not_(result_reg);  // safe not to zero extension

[Jakob Kummerow, 2014/03/19 12:00:30]

This comment doesn't make any sense, unless the reader knows that in one of the
places where you're putting it there used to be a movzx_b instruction.
Also, comments should be complete sentences with proper grammar, capitalization
and punctuation.

   jmp(&done, Label::kNear);
   bind(&conv_failure);
+  sar(result_reg, 31);
+  ucomisd(input_reg, scratch_reg);
+  j(above_equal, &done, Label::kNear);
   Set(result_reg, Immediate(0));
-  ucomisd(input_reg, scratch_reg);
-  j(below, &done, Label::kNear);
-  Set(result_reg, Immediate(255));
   bind(&done);
 }
 
 
 void MacroAssembler::ClampUint8(Register reg) {
   Label done;
   test(reg, Immediate(0xFFFFFF00));
   j(zero, &done, Label::kNear);
-  setcc(negative, reg);  // 1 if negative, 0 if positive.
-  dec_b(reg);  // 0 if negative, 255 if positive.
+  sar(reg, 31);
+  not_(reg);  // safe not to zero extension
   bind(&done);
 }
 
 
 void MacroAssembler::SlowTruncateToI(Register result_reg,
                                      Register input_reg,
                                      int offset) {
   DoubleToIStub stub(input_reg, result_reg, offset, true);
   call(stub.GetCode(isolate()), RelocInfo::CODE_TARGET);
 }
 
 
 void MacroAssembler::TruncateDoubleToI(Register result_reg,
                                        XMMRegister input_reg) {
   Label done;
   cvttsd2si(result_reg, Operand(input_reg));
-  cmp(result_reg, 0x80000000u);
-  j(not_equal, &done, Label::kNear);
+  cmp(result_reg, 0x1);
+  j(no_overflow, &done, Label::kNear);
 
   sub(esp, Immediate(kDoubleSize));
   movsd(MemOperand(esp, 0), input_reg);
   SlowTruncateToI(result_reg, esp, 0);
   add(esp, Immediate(kDoubleSize));
   bind(&done);
 }
 
 
 void MacroAssembler::TruncateX87TOSToI(Register result_reg) {
@@ skipping 96 matching lines @@
       SlowTruncateToI(result_reg, esp, 0);
       add(esp, Immediate(kDoubleSize));
     } else {
       fstp(0);
       SlowTruncateToI(result_reg, input_reg);
     }
   } else if (CpuFeatures::IsSupported(SSE2)) {
     CpuFeatureScope scope(this, SSE2);
     movsd(xmm0, FieldOperand(input_reg, HeapNumber::kValueOffset));
     cvttsd2si(result_reg, Operand(xmm0));
-    cmp(result_reg, 0x80000000u);
-    j(not_equal, &done, Label::kNear);
+    cmp(result_reg, 0x1);
+    j(no_overflow, &done, Label::kNear);
     // Check if the input was 0x8000000 (kMinInt).
     // If no, then we got an overflow and we deoptimize.
     ExternalReference min_int = ExternalReference::address_of_min_int();
     ucomisd(xmm0, Operand::StaticVariable(min_int));
     j(not_equal, &slow_case, Label::kNear);
     j(parity_even, &slow_case, Label::kNear);  // NaN.
     jmp(&done, Label::kNear);
 
     // Slow case.
     bind(&slow_case);
@@ skipping 3232 matching lines @@
   imul(dividend);
   if (divisor > 0 && ms.multiplier() < 0) add(edx, dividend);
   if (divisor < 0 && ms.multiplier() > 0) sub(edx, dividend);
   if (ms.shift() > 0) sar(edx, ms.shift());
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32