Recognize special comparisons via pattern matching on the hydrogen graph, 2nd attempt.

src/hydrogen-instructions.cc

 // Copyright 2011 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 769 matching lines @@
 }
 
 
 void HTypeofIsAndBranch::PrintDataTo(StringStream* stream) {
   value()->PrintNameTo(stream);
   stream->Add(" == %o", *type_literal_);
   HControlInstruction::PrintDataTo(stream);
 }
 
 
+HValue* HConstant::Canonicalize() {
+  return HasNoUses()&& !IsBlockEntry() ? NULL : this;

[Kevin Millikin (Chromium), 2011/10/19 07:24:41]

Missing a space before &&, also below.

[Sven Panne, 2011/10/19 07:33:32]

Done.

+}
+
+
+HValue* HTypeof::Canonicalize() {
+  return HasNoUses()&& !IsBlockEntry() ? NULL : this;
+}
+
+
 void HTypeof::PrintDataTo(StringStream* stream) {
   value()->PrintNameTo(stream);
 }
 
 
 void HChange::PrintDataTo(StringStream* stream) {
   HUnaryOperation::PrintDataTo(stream);
   stream->Add(" %s to %s", from().Mnemonic(), to().Mnemonic());
 
   if (CanTruncateToInt32()) stream->Add(" truncating-int32");
@@ skipping 1164 matching lines @@
 
 
 void HCheckPrototypeMaps::Verify() {
   HInstruction::Verify();
   ASSERT(HasNoUses());
 }
 
 #endif
 
 } }  // namespace v8::internal