Introduce %_IsMinusZero.

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index 147563e90104c7d094c93b937bb91c0f34534fc6..07da8f4ca18092966347c409bd95c1c689a30bb3 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -8778,6 +8778,15 @@ void HOptimizedGraphBuilder::GenerateIsFunction(CallRuntime* call) {
 }
 
 
+void HOptimizedGraphBuilder::GenerateIsMinusZero(CallRuntime* call) {
+  ASSERT(call->arguments()->length() == 1);
+  CHECK_ALIVE(VisitForValue(call->arguments()->at(0)));
+  HValue* value = Pop();
+  HCompareMinusZeroAndBranch* result = New<HCompareMinusZeroAndBranch>(value);
+  return ast_context()->ReturnControl(result, call->id());
+}
+
+
 void HOptimizedGraphBuilder::GenerateHasCachedArrayIndex(CallRuntime* call) {
   ASSERT(call->arguments()->length() == 1);
   CHECK_ALIVE(VisitForValue(call->arguments()->at(0)));