Introduce %_IsMinusZero.

src/hydrogen-instructions.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 2926 matching lines @@
   return false;
 }
 
 
 void HCompareHoleAndBranch::InferRepresentation(
     HInferRepresentationPhase* h_infer) {
   ChangeRepresentation(value()->representation());
 }
 
 
+bool HCompareMinusZeroAndBranch::KnownSuccessorBlock(HBasicBlock** block) {
+  if (value()->representation().IsSmiOrInteger32()) {
+    // A Smi or Integer32 cannot contain minus zero.
+    *block = SecondSuccessor();
+    return true;
+  }
+  *block = NULL;
+  return false;
+}
+
+
+void HCompareMinusZeroAndBranch::InferRepresentation(
+    HInferRepresentationPhase* h_infer) {
+  ChangeRepresentation(value()->representation());
+}
+
+
+
 void HGoto::PrintDataTo(StringStream* stream) {
   stream->Add("B%d", SuccessorAt(0)->block_id());
 }
 
 
 void HCompareNumericAndBranch::InferRepresentation(
     HInferRepresentationPhase* h_infer) {
   Representation left_rep = left()->representation();
   Representation right_rep = right()->representation();
   Representation observed_left = observed_input_representation(0);
@@ skipping 1369 matching lines @@
       break;
     case kExternalMemory:
       stream->Add("[external-memory]");
       break;
   }
 
   stream->Add("@%d", offset());
 }
 
 } }  // namespace v8::internal