Crankshaft: Recognize (i >>> 0) === i for integer32 inputs and replace

src/hydrogen.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 10023 matching lines @@
 Representation HOptimizedGraphBuilder::ToRepresentation(TypeInfo info) {
   if (info.IsUninitialized()) return Representation::None();
   if (info.IsSmi()) return Representation::Integer32();
   if (info.IsInteger32()) return Representation::Integer32();
   if (info.IsDouble()) return Representation::Double();
   if (info.IsNumber()) return Representation::Double();
   return Representation::Tagged();
 }
 
 
+void HOptimizedGraphBuilder::HandleTripleShiftZeroCompare(
+    CompareOperation* expr,
+    HValue* input) {
+  // (i >>> 0) === i is transformed to i >= 0.
+  // (i >>> 0) !== i is transformed to i < 0.
+  Token::Value op = (expr->op() == Token::EQ_STRICT) ? Token::GTE : Token::LT;
+  HCompareIDAndBranch* compare =
+      new(zone()) HCompareIDAndBranch(input, graph()->GetConstant0(), op);
+  compare->set_observed_input_representation(Representation::Integer32(),
+                                             Representation::Integer32());
+  compare->set_position(expr->position());
+  return ast_context()->ReturnControl(compare, expr->id());
+}
+
+
 void HOptimizedGraphBuilder::HandleLiteralCompareTypeof(CompareOperation* expr,
                                                         HTypeof* typeof_expr,
                                                         Handle<String> check) {
   // Note: The HTypeof itself is removed during canonicalization, if possible.
   HValue* value = typeof_expr->value();
   HTypeofIsAndBranch* instr = new(zone()) HTypeofIsAndBranch(value, check);
   instr->set_position(expr->position());
   return ast_context()->ReturnControl(instr, expr->id());
 }
 
@@ skipping 1818 matching lines @@
     }
   }
 
 #ifdef DEBUG
   if (graph_ != NULL) graph_->Verify(false);  // No full verify.
   if (allocator_ != NULL) allocator_->Verify();
 #endif
 }
 
 } }  // namespace v8::internal