Introduce %_IsMinusZero.

src/ia32/lithium-codegen-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 2652 matching lines @@
     __ fstp_d(MemOperand(esp, 0));
   }
 
   __ add(esp, Immediate(kDoubleSize));
   int offset = sizeof(kHoleNanUpper32);
   __ cmp(MemOperand(esp, -offset), Immediate(kHoleNanUpper32));
   EmitBranch(instr, equal);
 }
 
 
+void LCodeGen::DoCompareMinusZeroAndBranch(LCompareMinusZeroAndBranch* instr) {
+  Representation rep = instr->hydrogen()->value()->representation();
+  ASSERT(!rep.IsInteger32());
+  Label if_false;
+  Register scratch = ToRegister(instr->temp());
+
+  if (rep.IsDouble()) {
+    CpuFeatureScope use_sse2(masm(), SSE2);
+    XMMRegister value = ToDoubleRegister(instr->value());
+    XMMRegister xmm_scratch = double_scratch0();
+    __ xorps(xmm_scratch, xmm_scratch);
+    __ ucomisd(xmm_scratch, value);
+    __ j(not_equal, &if_false);
+    __ movmskpd(scratch, value);
+    __ test(scratch, Immediate(1));
+    EmitBranch(instr, not_zero);
+  } else {
+    Register value = ToRegister(instr->value());
+    Handle<Map> map = masm()->isolate()->factory()->heap_number_map();
+    __ CheckMap(eax, map, &if_false, DO_SMI_CHECK);
+    __ cmp(FieldOperand(value, HeapNumber::kExponentOffset),
+           Immediate(0x80000000));
+    __ j(not_equal, &if_false);
+    __ cmp(FieldOperand(value, HeapNumber::kMantissaOffset),
+           Immediate(0x00000000));
+    EmitBranch(instr, equal);
+  }
+
+  __ bind(&if_false);
+  EmitFalseBranch(instr, no_condition);
+}
+
+
 Condition LCodeGen::EmitIsObject(Register input,
                                  Register temp1,
                                  Label* is_not_object,
                                  Label* is_object) {
   __ JumpIfSmi(input, is_not_object);
 
   __ cmp(input, isolate()->factory()->null_value());
   __ j(equal, is_object);
 
   __ mov(temp1, FieldOperand(input, HeapObject::kMapOffset));
@@ skipping 3753 matching lines @@
                               FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32