Add CFG and SSA form checkers in the optimizing compiler.

Checks performed on control-flow graphs:
- Ensure that the predecessors and successors of a basic block are
  consistent within a control-flow graph.
- Ensure basic blocks end with a branch instruction.
- Detect phi functions listed in non-phi instruction lists and vice
  versa.
- Ensure a block's instructions (and phi functions) are associated
  with this very block.

Checks performed on SSA form graphs:
- Ensure an instruction dominates all its uses.
- Ensure there are no critical edges.

Change-Id: I1c12b4a61ecf608682152c897980ababa7eca847

1 files changed, 80 insertions, 0 deletions

diff --git a/compiler/optimizing/graph_checker.h b/compiler/optimizing/graph_checker.h
new file mode 100644
index 0000000000..8ddd399456
--- /dev/null
+++ b/compiler/optimizing/graph_checker.h
@@ -0,0 +1,80 @@
+/*
+ * 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_GRAPH_CHECKER_H_
+#define ART_COMPILER_OPTIMIZING_GRAPH_CHECKER_H_
+
+#include "nodes.h"
+
+namespace art {
+
+// A control-flow graph visitor performing various checks.
+class GraphChecker : public HGraphVisitor {
+ public:
+  GraphChecker(ArenaAllocator* allocator, HGraph* graph)
+    : HGraphVisitor(graph),
+      allocator_(allocator),
+      errors_(allocator, 0) {}
+
+  // Check `block`.
+  virtual void VisitBasicBlock(HBasicBlock* block) OVERRIDE;
+
+  // Check `instruction`.
+  virtual void VisitInstruction(HInstruction* instruction) OVERRIDE;
+
+  // Was the last visit of the graph valid?
+  bool IsValid() const {
+    return errors_.IsEmpty();
+  }
+
+  // Get the list of detected errors.
+  const GrowableArray<std::string>& GetErrors() const {
+    return errors_;
+  }
+
+ protected:
+  ArenaAllocator* const allocator_;
+  // The block currently visited.
+  HBasicBlock* current_block_ = nullptr;
+  // Errors encountered while checking the graph.
+  GrowableArray<std::string> errors_;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(GraphChecker);
+};
+
+
+// An SSA graph visitor performing various checks.
+class SSAChecker : public GraphChecker {
+ public:
+  typedef GraphChecker super_type;
+
+  SSAChecker(ArenaAllocator* allocator, HGraph* graph)
+    : GraphChecker(allocator, graph) {}
+
+  // Perform SSA form checks on `block`.
+  virtual void VisitBasicBlock(HBasicBlock* block) OVERRIDE;
+
+  // Perform SSA form checks on `instruction`.
+  virtual void VisitInstruction(HInstruction* instruction) OVERRIDE;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(SSAChecker);
+};
+
+}  // namespace art
+
+#endif  // ART_COMPILER_OPTIMIZING_GRAPH_CHECKER_H_