Initiate a constant propagation pass in the optimizing compiler.
- Perform constant folding on int and long additions and subtractions in
the optimizing compiler.
- Apply constant folding to conditions and comparisons.
Change-Id: Ic88783a3c975fda777c74c531e257fa777be42eb
diff --git a/compiler/optimizing/constant_propagation.cc b/compiler/optimizing/constant_propagation.cc
new file mode 100644
index 0000000..d675164
--- /dev/null
+++ b/compiler/optimizing/constant_propagation.cc
@@ -0,0 +1,47 @@
+/*
+ * 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 "constant_propagation.h"
+
+namespace art {
+
+void ConstantPropagation::Run() {
+ // Process basic blocks in reverse post-order in the dominator tree,
+ // so that an instruction turned into a constant, used as input of
+ // another instruction, may possibly be used to turn that second
+ // instruction into a constant as well.
+ for (HReversePostOrderIterator it(*graph_); !it.Done(); it.Advance()) {
+ HBasicBlock* block = it.Current();
+ // Traverse this block's instructions in (forward) order and
+ // replace the ones that can be statically evaluated by a
+ // compile-time counterpart.
+ for (HInstructionIterator it(block->GetInstructions());
+ !it.Done(); it.Advance()) {
+ HInstruction* inst = it.Current();
+ // Constant folding: replace `c <- a op b' with a compile-time
+ // evaluation of `a op b' if `a' and `b' are constant.
+ if (inst->IsBinaryOperation()) {
+ HConstant* constant =
+ inst->AsBinaryOperation()->TryStaticEvaluation(graph_->GetArena());
+ if (constant != nullptr) {
+ inst->GetBlock()->ReplaceAndRemoveInstructionWith(inst, constant);
+ }
+ }
+ }
+ }
+}
+
+} // namespace art