Introduce %_IsMinusZero.

src/x64/lithium-codegen-x64.cc

 // Copyright 2013 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 2228 matching lines @@
   __ subq(rsp, Immediate(kDoubleSize));
   __ movsd(MemOperand(rsp, 0), input_reg);
   __ addq(rsp, Immediate(kDoubleSize));
 
   int offset = sizeof(kHoleNanUpper32);
   __ cmpl(MemOperand(rsp, -offset), Immediate(kHoleNanUpper32));
   EmitBranch(instr, equal);
 }
 
 
+void LCodeGen::DoCompareMinusZeroAndBranch(LCompareMinusZeroAndBranch* instr) {
+  Representation rep = instr->hydrogen()->value()->representation();
+  ASSERT(!rep.IsInteger32());
+  Label if_false;
+
+  if (rep.IsDouble()) {
+    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(kScratchRegister, value);
+    __ testl(kScratchRegister, Immediate(1));
+    EmitBranch(instr, not_zero);
+  } else {
+    Register value = ToRegister(instr->value());
+    Handle<Map> map = masm()->isolate()->factory()->heap_number_map();
+    __ CheckMap(rax, map, &if_false, DO_SMI_CHECK);
+    __ cmpl(FieldOperand(value, HeapNumber::kExponentOffset),
+            Immediate(0x80000000));
+    __ j(not_equal, &if_false);
+    __ cmpl(FieldOperand(value, HeapNumber::kMantissaOffset),
+            Immediate(0x00000000));
+    EmitBranch(instr, equal);
+  }
+
+  __ bind(&if_false);
+  EmitFalseBranch(instr, always);
+}
+
+
 Condition LCodeGen::EmitIsObject(Register input,
                                  Label* is_not_object,
                                  Label* is_object) {
   ASSERT(!input.is(kScratchRegister));
 
   __ JumpIfSmi(input, is_not_object);
 
   __ CompareRoot(input, Heap::kNullValueRootIndex);
   __ j(equal, is_object);
 
@@ skipping 3375 matching lines @@
                                FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64