From 72bceff11a98cc1ecdb64a6fae16c521f99ec6a7 Mon Sep 17 00:00:00 2001 From: Roland Levillain Date: Mon, 15 Sep 2014 18:29:00 +0100 Subject: Initiate a dead code elimination pass in the optimizing compiler. Change-Id: Ie9db5d8e2c2c30e34145a0f7d2386b8ec58cfc4e --- compiler/optimizing/dead_code_elimination.cc | 45 ++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+) create mode 100644 compiler/optimizing/dead_code_elimination.cc (limited to 'compiler/optimizing/dead_code_elimination.cc') diff --git a/compiler/optimizing/dead_code_elimination.cc b/compiler/optimizing/dead_code_elimination.cc new file mode 100644 index 0000000000..2f881d1b6d --- /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 -- cgit v1.2.3-59-g8ed1b