Introduce %_IsMinusZero.

src/x64/lithium-x64.h

Index: src/x64/lithium-x64.h
diff --git a/src/x64/lithium-x64.h b/src/x64/lithium-x64.h
index 17e74aa13614f6d8ae1c271ff5625ff757584dd8..6e236c7878db0f9cf60fe790ae753c2ab54c65ba 100644
--- a/src/x64/lithium-x64.h
+++ b/src/x64/lithium-x64.h
@@ -72,6 +72,7 @@ class LCodeGen;
   V(ClampIToUint8)                              \
   V(ClampTToUint8)                              \
   V(ClassOfTestAndBranch)                       \
+  V(CompareMinusZeroAndBranch)                  \
   V(CompareNumericAndBranch)                    \
   V(CmpObjectEqAndBranch)                       \
   V(CmpHoleAndBranch)                           \
@@ -874,6 +875,21 @@ class LCmpHoleAndBranch V8_FINAL : public LControlInstruction<1, 0> {
 };
 
 
+class LCompareMinusZeroAndBranch V8_FINAL : public LControlInstruction<1, 0> {
+ public:
+  explicit LCompareMinusZeroAndBranch(LOperand* value) {
+    inputs_[0] = value;
+  }
+
+  LOperand* value() { return inputs_[0]; }
+
+  DECLARE_CONCRETE_INSTRUCTION(CompareMinusZeroAndBranch,
+                               "cmp-minus-zero-and-branch")
+  DECLARE_HYDROGEN_ACCESSOR(CompareMinusZeroAndBranch)
+};
+
+
+
 class LIsObjectAndBranch V8_FINAL : public LControlInstruction<1, 0> {
  public:
   explicit LIsObjectAndBranch(LOperand* value) {