From 86ea7eeabe30c98bbe1651a51d03cb89776724e7 Mon Sep 17 00:00:00 2001
From: David Brazdil <dbrazdil@google.com>
Date: Tue, 16 Feb 2016 09:26:07 +0000
Subject: Build dominator tree before generating HInstructions

Second CL in the series of merging HGraphBuilder and SsaBuilder. This
patch refactors the builders so that dominator tree can be built
before any HInstructions are generated. This puts the SsaBuilder
removal of HLoadLocals/HStoreLocals straight after HGraphBuilder's
HInstruction generation phase. Next CL will therefore be able to
merge them.

This patch also adds util classes for iterating bytecode and switch
tables which allowed to simplify the code.

Bug: 27894376
Change-Id: Ic425d298b2e6e7980481ed697230b1a0b7904526
---
 compiler/optimizing/block_builder.h | 88 +++++++++++++++++++++++++++++++++++++
 1 file changed, 88 insertions(+)
 create mode 100644 compiler/optimizing/block_builder.h

(limited to 'compiler/optimizing/block_builder.h')

diff --git a/compiler/optimizing/block_builder.h b/compiler/optimizing/block_builder.h
new file mode 100644
index 0000000000..1be0b4ce98
--- /dev/null
+++ b/compiler/optimizing/block_builder.h
@@ -0,0 +1,88 @@
+/*
+ * Copyright (C) 2016 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_BLOCK_BUILDER_H_
+#define ART_COMPILER_OPTIMIZING_BLOCK_BUILDER_H_
+
+#include "base/arena_containers.h"
+#include "base/arena_object.h"
+#include "dex_file.h"
+#include "nodes.h"
+
+namespace art {
+
+class HBasicBlockBuilder : public ValueObject {
+ public:
+  HBasicBlockBuilder(HGraph* graph,
+                     const DexFile* const dex_file,
+                     const DexFile::CodeItem& code_item)
+      : arena_(graph->GetArena()),
+        graph_(graph),
+        dex_file_(dex_file),
+        code_item_(code_item),
+        branch_targets_(code_item.insns_size_in_code_units_,
+                        nullptr,
+                        arena_->Adapter(kArenaAllocGraphBuilder)),
+        throwing_blocks_(kDefaultNumberOfThrowingBlocks, arena_->Adapter(kArenaAllocGraphBuilder)),
+        number_of_branches_(0u) {}
+
+  // Creates basic blocks in `graph_` at branch target dex_pc positions of the
+  // `code_item_`. Blocks are connected but left unpopulated with instructions.
+  // TryBoundary blocks are inserted at positions where control-flow enters/
+  // exits a try block.
+  bool Build();
+
+  size_t GetNumberOfBranches() const { return number_of_branches_; }
+  HBasicBlock* GetBlockAt(uint32_t dex_pc) const { return branch_targets_[dex_pc]; }
+
+ private:
+  // Creates a basic block starting at given `dex_pc`.
+  HBasicBlock* MaybeCreateBlockAt(uint32_t dex_pc);
+
+  // Creates a basic block for bytecode instructions at `semantic_dex_pc` and
+  // stores it under the `store_dex_pc` key. This is used when multiple blocks
+  // share the same semantic dex_pc, e.g. when building switch decision trees.
+  HBasicBlock* MaybeCreateBlockAt(uint32_t semantic_dex_pc, uint32_t store_dex_pc);
+
+  bool CreateBranchTargets();
+  void ConnectBasicBlocks();
+  void InsertTryBoundaryBlocks();
+
+  // Helper method which decides whether `catch_block` may have live normal
+  // predecessors and thus whether a synthetic catch block needs to be created
+  // to avoid mixing normal and exceptional predecessors.
+  // Should only be called during InsertTryBoundaryBlocks on blocks at catch
+  // handler dex_pcs.
+  bool MightHaveLiveNormalPredecessors(HBasicBlock* catch_block);
+
+  ArenaAllocator* const arena_;
+  HGraph* const graph_;
+
+  const DexFile* const dex_file_;
+  const DexFile::CodeItem& code_item_;
+
+  ArenaVector<HBasicBlock*> branch_targets_;
+  ArenaVector<HBasicBlock*> throwing_blocks_;
+  size_t number_of_branches_;
+
+  static constexpr size_t kDefaultNumberOfThrowingBlocks = 2u;
+
+  DISALLOW_COPY_AND_ASSIGN(HBasicBlockBuilder);
+};
+
+}  // namespace art
+
+#endif  // ART_COMPILER_OPTIMIZING_BLOCK_BUILDER_H_
-- 
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