Implement simple dead store elimination.

runtime/vm/intermediate_language.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/intermediate_language.h"
 
 #include "vm/bigint_operations.h"
 #include "vm/bit_vector.h"
 #include "vm/cpu.h"
 #include "vm/dart_entry.h"
@@ skipping 625 matching lines @@
   while (!result->IsBlockEntry()) result = result->previous();
   return result->AsBlockEntry();
 }
 
 
 void ForwardInstructionIterator::RemoveCurrentFromGraph() {
   current_ = current_->RemoveFromGraph(true);  // Set current_ to previous.
 }
 
 
+void BackwardInstructionIterator::RemoveCurrentFromGraph() {
+  current_ = current_->RemoveFromGraph(false);  // Set current_ to next.
+}
+
+
 // Default implementation of visiting basic blocks.  Can be overridden.
 void FlowGraphVisitor::VisitBlocks() {
   ASSERT(current_iterator_ == NULL);
   for (intptr_t i = 0; i < block_order_.length(); ++i) {
     BlockEntryInstr* entry = block_order_[i];
     entry->Accept(this);
     ForwardInstructionIterator it(entry);
     current_iterator_ = &it;
     for (; !it.Done(); it.Advance()) {
       it.Current()->Accept(this);
@@ skipping 2740 matching lines @@
     case Token::kTRUNCDIV: return 0;
     case Token::kMOD: return 1;
     default: UNIMPLEMENTED(); return -1;
   }
 }
 
 
 #undef __
 
 }  // namespace dart