Guard against misuse of IfBuilder.

src/hydrogen.cc

 // Copyright 2013 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 777 matching lines @@
     compare->SetSuccessorAt(0, first_true_block_);
     compare->SetSuccessorAt(1, first_false_block_);
   }
   builder_->FinishCurrentBlock(compare);
   needs_compare_ = false;
   return compare;
 }
 
 
 void HGraphBuilder::IfBuilder::Or() {
+  ASSERT(!needs_compare_);
   ASSERT(!did_and_);
   did_or_ = true;
   HEnvironment* env = first_false_block_->last_environment();
   if (split_edge_merge_block_ == NULL) {
     split_edge_merge_block_ =
         builder_->CreateBasicBlock(env->Copy());
     builder_->GotoNoSimulate(first_true_block_, split_edge_merge_block_);
     first_true_block_ = split_edge_merge_block_;
   }
   builder_->set_current_block(first_false_block_);
   first_false_block_ = builder_->CreateBasicBlock(env->Copy());
 }
 
 
 void HGraphBuilder::IfBuilder::And() {
+  ASSERT(!needs_compare_);
   ASSERT(!did_or_);
   did_and_ = true;
   HEnvironment* env = first_false_block_->last_environment();
   if (split_edge_merge_block_ == NULL) {
     split_edge_merge_block_ = builder_->CreateBasicBlock(env->Copy());
     builder_->GotoNoSimulate(first_false_block_, split_edge_merge_block_);
     first_false_block_ = split_edge_merge_block_;
   }
   builder_->set_current_block(first_true_block_);
   first_true_block_ = builder_->CreateBasicBlock(env->Copy());
@@ skipping 9025 matching lines @@
   if (ShouldProduceTraceOutput()) {
     isolate()->GetHTracer()->TraceHydrogen(name(), graph_);
   }
 
 #ifdef DEBUG
   graph_->Verify(false);  // No full verify.
 #endif
 }
 
 } }  // namespace v8::internal