Refactored FlowGraphBuilder into a separate FlowGraph representation.

runtime/vm/flow_graph.h

Index: runtime/vm/flow_graph.h
diff --git a/runtime/vm/flow_graph.h b/runtime/vm/flow_graph.h
new file mode 100644
index 0000000000000000000000000000000000000000..5b3462d2089d4e110971082d121d77dfacd8c9ec
--- /dev/null
+++ b/runtime/vm/flow_graph.h
@@ -0,0 +1,110 @@
+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#ifndef VM_FLOW_GRAPH_H_
+#define VM_FLOW_GRAPH_H_
+
+#include "vm/ast.h"

[Kevin Millikin (Google), 2012/08/16 08:09:57]

Are you sure you need to include this?  I can't immediately see why.

[zerny-google, 2012/08/16 11:52:27]

Thanks. It was the parser.h I needed.

+#include "vm/parser.h"
+#include "vm/growable_array.h"
+#include "vm/intermediate_language.h"
+
+namespace dart {
+
+// Class to incapsulate the construction and manipulation of the flow graph.
+class FlowGraph: public ValueObject {
+ public:
+  // Build a flow graph from a parsed function's AST.
+  explicit FlowGraph(const ParsedFunction& parsed_function);
+
+  // Function properties.
+  const ParsedFunction& parsed_function() const {
+    return parsed_function_;
+  }
+  intptr_t parameter_count() const {
+    return copied_parameter_count_ + non_copied_parameter_count_;
+  }
+  intptr_t variable_count() const {
+    return parameter_count() + stack_local_count_;
+  }
+  intptr_t stack_local_count() const {
+    return stack_local_count_;
+  }
+  intptr_t copied_parameter_count() const {
+    return copied_parameter_count_;
+  }
+  intptr_t non_copied_parameter_count() const {
+    return non_copied_parameter_count_;
+  }
+
+  // Flow graph orders.
+  const GrowableArray<BlockEntryInstr*>& preorder() const {
+    return preorder_;
+  }
+  const GrowableArray<BlockEntryInstr*>& postorder() const {
+    return postorder_;
+  }
+  const GrowableArray<BlockEntryInstr*>& reverse_postorder() const {
+    return reverse_postorder_;
+  }
+
+  intptr_t max_virtual_register_number() const {
+    return current_ssa_temp_index();
+  }
+
+  // Operations on the flow graph.
+  void BuildGraph();
+  void ComputeSSA();
+
+  // TODO(zerny): Once the SSA is feature complete this should be removed.
+  void Bailout(const char* reason);
+
+ private:
+  void ComputeOrders();

[Kevin Millikin (Google), 2012/08/16 08:09:57]

I like the name DiscoverBlocks better.  It seems more central that this is the
unique function that makes the implicit basic-block structure explicit.

[zerny-google, 2012/08/16 11:52:27]

Ok

+
+  const ParsedFunction& parsed_function_;

[Kevin Millikin (Google), 2012/08/16 08:09:57]

Member variables should all be at the end of the private: section and grouped
together.

[zerny-google, 2012/08/16 11:52:27]

Done.

+  const intptr_t copied_parameter_count_;
+  const intptr_t non_copied_parameter_count_;
+  const intptr_t stack_local_count_;
+  GraphEntryInstr* graph_entry_;
+  GrowableArray<BlockEntryInstr*> preorder_;
+  GrowableArray<BlockEntryInstr*> postorder_;
+  GrowableArray<BlockEntryInstr*> reverse_postorder_;
+
+  // SSA transformation methods and fields.
+  void ComputeDominators(
+      GrowableArray<BlockEntryInstr*>* preorder,
+      GrowableArray<intptr_t>* parent,
+      GrowableArray<BitVector*>* dominance_frontier);
+
+  void CompressPath(
+      intptr_t start_index,
+      intptr_t current_index,
+      GrowableArray<intptr_t>* parent,
+      GrowableArray<intptr_t>* label);
+
+  void Rename(GrowableArray<PhiInstr*>* live_phis);
+  void RenameRecursive(
+      BlockEntryInstr* block_entry,
+      GrowableArray<Value*>* env,
+      GrowableArray<PhiInstr*>* live_phis);
+
+  void InsertPhis(
+      const GrowableArray<BlockEntryInstr*>& preorder,
+      const GrowableArray<BitVector*>& assigned_vars,
+      const GrowableArray<BitVector*>& dom_frontier);
+
+  void MarkLivePhis(GrowableArray<PhiInstr*>* live_phis);
+
+  intptr_t current_ssa_temp_index() const { return current_ssa_temp_index_; }
+  intptr_t alloc_ssa_temp_index() { return current_ssa_temp_index_++; }
+
+  GrowableArray<intptr_t> parent_;

[Kevin Millikin (Google), 2012/08/16 08:09:57]

These variables (parent_ and assigned_vars_) should have a comment that they are
used for SSA computation and but not maintained afterward.

[zerny-google, 2012/08/16 11:52:27]

Done.

+  GrowableArray<BitVector*> assigned_vars_;
+  intptr_t current_ssa_temp_index_;
+};
+
+}  // namespace dart
+
+#endif  // VM_FLOW_GRAPH_H_