Introduce %_IsMinusZero.

src/arm/lithium-codegen-arm.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 2454 matching lines @@
   __ VFPCompareAndSetFlags(input_reg, input_reg);
   EmitFalseBranch(instr, vc);
 
   Register scratch = scratch0();
   __ VmovHigh(scratch, input_reg);
   __ cmp(scratch, Operand(kHoleNanUpper32));
   EmitBranch(instr, eq);
 }
 
 
+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()) {
+    DwVfpRegister value = ToDoubleRegister(instr->value());
+    __ VFPCompareAndSetFlags(value, 0.0);
+    __ b(ne, &if_false);
+    __ VmovHigh(scratch, value);
+    __ cmp(scratch, Operand(0x80000000));
+  } else {
+    Register value = ToRegister(instr->value());
+    __ CheckMap(
+        value, scratch, Heap::kHeapNumberMapRootIndex, &if_false, DO_SMI_CHECK);
+    __ ldr(scratch, FieldMemOperand(value, HeapNumber::kExponentOffset));
+    __ ldr(ip, FieldMemOperand(value, HeapNumber::kMantissaOffset));
+    __ cmp(scratch, Operand(0x80000000));
+    __ cmp(ip, Operand(0x00000000), eq);
+  }
+  EmitBranch(instr, eq);
+
+  __ bind(&if_false);
+  EmitFalseBranch(instr, al);
+}
+
+
 Condition LCodeGen::EmitIsObject(Register input,
                                  Register temp1,
                                  Label* is_not_object,
                                  Label* is_object) {
   Register temp2 = scratch0();
   __ JumpIfSmi(input, is_not_object);
 
   __ LoadRoot(temp2, Heap::kNullValueRootIndex);
   __ cmp(input, temp2);
   __ b(eq, is_object);
@@ skipping 3390 matching lines @@
   __ sub(scratch, result, Operand::PointerOffsetFromSmiKey(index));
   __ ldr(result, FieldMemOperand(scratch,
                                  FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal