MIPS: Introduce %_IsMinusZero.

src/mips/lithium-codegen-mips.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 2293 matching lines @@
 
   DoubleRegister input_reg = ToDoubleRegister(instr->object());
   EmitFalseBranchF(instr, eq, input_reg, input_reg);
 
   Register scratch = scratch0();
   __ FmoveHigh(scratch, input_reg);
   EmitBranch(instr, eq, scratch, Operand(kHoleNanUpper32));
 }
 
 
+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()) {
+    DoubleRegister value = ToDoubleRegister(instr->value());
+    __ BranchF(&if_false, NULL, ne, value, kDoubleRegZero);
+    __ FmoveHigh(scratch, value);
+    __ li(at, 0x80000000);
+  } else {
+    Register value = ToRegister(instr->value());
+    __ CheckMap(
+        value, scratch, Heap::kHeapNumberMapRootIndex, &if_false, DO_SMI_CHECK);
+    __ lw(scratch, FieldMemOperand(value, HeapNumber::kExponentOffset));
+    __ Branch(&if_false, ne, scratch, Operand(0x80000000));
+    __ lw(scratch, FieldMemOperand(value, HeapNumber::kMantissaOffset));
+    __ mov(at, zero_reg);
+  }
+  EmitBranch(instr, eq, scratch, Operand(at));
+
+  __ bind(&if_false);
+  EmitFalseBranchF(instr, al, kDoubleRegZero, kDoubleRegZero);
+}
+
+
 Condition LCodeGen::EmitIsObject(Register input,
                                  Register temp1,
                                  Register temp2,
                                  Label* is_not_object,
                                  Label* is_object) {
   __ JumpIfSmi(input, is_not_object);
 
   __ LoadRoot(temp2, Heap::kNullValueRootIndex);
   __ Branch(is_object, eq, input, Operand(temp2));
 
@@ skipping 3530 matching lines @@
   __ Subu(scratch, result, scratch);
   __ lw(result, FieldMemOperand(scratch,
                                 FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal