Introduce %_IsMinusZero.

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index b9c0ca9fce3d3e67b3e3a7f6b050c7f2f3ae6376..fc8f6addb2c7c632e2c3b5f816ca51cdacaecc0a 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -100,6 +100,7 @@ class LChunkBuilder;
   V(CompareNumericAndBranch)                   \
   V(CompareHoleAndBranch)                      \
   V(CompareGeneric)                            \
+  V(CompareMinusZeroAndBranch)                 \
   V(CompareObjectEqAndBranch)                  \
   V(CompareMap)                                \
   V(Constant)                                  \
@@ -4165,6 +4166,28 @@ class HCompareHoleAndBranch V8_FINAL : public HUnaryControlInstruction {
 };
 
 
+class HCompareMinusZeroAndBranch V8_FINAL : public HUnaryControlInstruction {
+ public:
+  DECLARE_INSTRUCTION_FACTORY_P1(HCompareMinusZeroAndBranch, HValue*);
+
+  virtual void InferRepresentation(
+      HInferRepresentationPhase* h_infer) V8_OVERRIDE;
+
+  virtual Representation RequiredInputRepresentation(int index) V8_OVERRIDE {
+    return representation();
+  }
+
+  virtual bool KnownSuccessorBlock(HBasicBlock** block) V8_OVERRIDE;
+
+  DECLARE_CONCRETE_INSTRUCTION(CompareMinusZeroAndBranch)
+
+ private:
+  explicit HCompareMinusZeroAndBranch(HValue* value)
+      : HUnaryControlInstruction(value, NULL, NULL) {
+  }
+};
+
+
 class HCompareObjectEqAndBranch : public HTemplateControlInstruction<2, 2> {
  public:
   HCompareObjectEqAndBranch(HValue* left,