Initiate a dead code elimination pass in the optimizing compiler.
Change-Id: Ie9db5d8e2c2c30e34145a0f7d2386b8ec58cfc4e
diff --git a/compiler/optimizing/dead_code_elimination.cc b/compiler/optimizing/dead_code_elimination.cc
new file mode 100644
index 0000000..2f881d1
--- /dev/null
+++ b/compiler/optimizing/dead_code_elimination.cc
@@ -0,0 +1,45 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "dead_code_elimination.h"
+
+#include "base/bit_vector-inl.h"
+
+namespace art {
+
+void DeadCodeElimination::Run() {
+ // Process basic blocks in post-order in the dominator tree, so that
+ // a dead instruction depending on another dead instruction is
+ // removed.
+ for (HPostOrderIterator b(*graph_); !b.Done(); b.Advance()) {
+ HBasicBlock* block = b.Current();
+ // Traverse this block's instructions in backward order and remove
+ // the unused ones.
+ HBackwardInstructionIterator i(block->GetInstructions());
+ // Skip the first iteration, as the last instruction of a block is
+ // a branching instruction.
+ DCHECK(i.Current()->IsControlFlow());
+ for (i.Advance(); !i.Done(); i.Advance()) {
+ HInstruction* inst = i.Current();
+ DCHECK(!inst->IsControlFlow());
+ if (!inst->HasSideEffects() && !inst->HasUses()) {
+ block->RemoveInstruction(inst);
+ }
+ }
+ }
+}
+
+} // namespace art