Build live-in, live-out and kill sets for each block.

This information will be used when computing live ranges of
instructions.

Change-Id: I345ee833c1ccb4a8e725c7976453f6d58d350d74

1 files changed, 101 insertions, 0 deletions

diff --git a/compiler/optimizing/ssa_liveness_analysis.h b/compiler/optimizing/ssa_liveness_analysis.h
new file mode 100644
index 0000000..6a901d1
--- /dev/null
+++ b/compiler/optimizing/ssa_liveness_analysis.h
@@ -0,0 +1,101 @@
+/*
+ * 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.
+ */
+
+#ifndef ART_COMPILER_OPTIMIZING_SSA_LIVENESS_ANALYSIS_H_
+#define ART_COMPILER_OPTIMIZING_SSA_LIVENESS_ANALYSIS_H_
+
+#include "nodes.h"
+
+namespace art {
+
+class BlockInfo : public ArenaObject {
+ public:
+  BlockInfo(ArenaAllocator* allocator, const HBasicBlock& block, size_t number_of_ssa_values)
+      : block_(block),
+        live_in_(allocator, number_of_ssa_values, false),
+        live_out_(allocator, number_of_ssa_values, false),
+        kill_(allocator, number_of_ssa_values, false) {
+    live_in_.ClearAllBits();
+    live_out_.ClearAllBits();
+    kill_.ClearAllBits();
+  }
+
+ private:
+  const HBasicBlock& block_;
+  ArenaBitVector live_in_;
+  ArenaBitVector live_out_;
+  ArenaBitVector kill_;
+
+  friend class SsaLivenessAnalysis;
+
+  DISALLOW_COPY_AND_ASSIGN(BlockInfo);
+};
+
+class SsaLivenessAnalysis : public ValueObject {
+ public:
+  explicit SsaLivenessAnalysis(const HGraph& graph)
+      : graph_(graph),
+        block_infos_(graph.GetArena(), graph.GetBlocks().Size()),
+        number_of_ssa_values_(0) {
+    block_infos_.SetSize(graph.GetBlocks().Size());
+  }
+
+  void Analyze();
+
+  BitVector* GetLiveInSet(const HBasicBlock& block) const {
+    return &block_infos_.Get(block.GetBlockId())->live_in_;
+  }
+
+  BitVector* GetLiveOutSet(const HBasicBlock& block) const {
+    return &block_infos_.Get(block.GetBlockId())->live_out_;
+  }
+
+  BitVector* GetKillSet(const HBasicBlock& block) const {
+    return &block_infos_.Get(block.GetBlockId())->kill_;
+  }
+
+ private:
+  // Give an SSA number to each instruction that defines a value used by another instruction.
+  void NumberInstructions();
+
+  // Compute live_in, live_out and kill sets.
+  void ComputeSets();
+
+  // Compute the initial live_in, live_out and kill sets, without analyzing
+  // backward branches.
+  void ComputeInitialSets();
+
+  // After computing the initial sets, this method does a fixed point
+  // calculation over the live_in and live_out set to take into account
+  // backwards branches.
+  void ComputeLiveInAndLiveOutSets();
+
+  // Update the live_in set of the block and returns whether it has changed.
+  bool UpdateLiveIn(const HBasicBlock& block);
+
+  // Update the live_out set of the block and returns whether it has changed.
+  bool UpdateLiveOut(const HBasicBlock& block);
+
+  const HGraph& graph_;
+  GrowableArray<BlockInfo*> block_infos_;
+  size_t number_of_ssa_values_;
+
+  DISALLOW_COPY_AND_ASSIGN(SsaLivenessAnalysis);
+};
+
+}  // namespace art
+
+#endif  // ART_COMPILER_OPTIMIZING_SSA_LIVENESS_ANALYSIS_H_