Introduce a nesting stack to the flow graph builder.

runtime/vm/flow_graph_builder.h

 // 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_BUILDER_H_
 #define VM_FLOW_GRAPH_BUILDER_H_
 
 #include "platform/assert.h"
 #include "platform/globals.h"
 #include "vm/allocation.h"
@@ skipping 88 matching lines @@
 
   Definition* JoinReturns(BlockEntryInstr** exit_block,
                           Instruction** last_instruction);
 
   FlowGraph* caller_graph_;
   Definition* call_;
   GrowableArray<Data> exits_;
 };
 
 
+class NestedStatement;

[srdjan, 2013/11/13 17:17:08]

Typically all forward class declarations are done in the beginning. 

[Kevin Millikin (Google), 2013/11/13 17:47:22]

I'll move it.

+
 // Build a flow graph from a parsed function's AST.
 class FlowGraphBuilder: public ValueObject {
  public:
   // The inlining context is NULL if not inlining.  The osr_id is the deopt
   // id of the OSR entry or Isolate::kNoDeoptId if not compiling for OSR.
   FlowGraphBuilder(ParsedFunction* parsed_function,
                    const Array& ic_data_array,
                    InlineExitCollector* exit_collector,
                    intptr_t osr_id);
 
@@ skipping 44 matching lines @@
   intptr_t temp_count() const { return temp_count_; }
   intptr_t AllocateTemp() { return temp_count_++; }
   void DeallocateTemps(intptr_t count) {
     ASSERT(temp_count_ >= count);
     temp_count_ -= count;
   }
 
   intptr_t args_pushed() const { return args_pushed_; }
   void add_args_pushed(intptr_t n) { args_pushed_ += n; }
 
+  NestedStatement* nesting_stack() const { return nesting_stack_; }
+
   // When compiling for OSR, remove blocks that are not reachable from the
   // OSR entry point.
   void PruneUnreachable();
 
  private:
+  friend class NestedStatement;  // Explicit access to nesting_stack_.
+
   intptr_t parameter_count() const {
     return num_copied_params_ + num_non_copied_params_;
   }
   intptr_t variable_count() const {
     return parameter_count() + num_stack_locals_;
   }
 
   ParsedFunction* parsed_function_;
   const Array& ic_data_array_;
 
   const intptr_t num_copied_params_;
   const intptr_t num_non_copied_params_;
   const intptr_t num_stack_locals_;  // Does not include any parameters.
   InlineExitCollector* const exit_collector_;
   ZoneGrowableArray<const Field*>* guarded_fields_;
 
   intptr_t last_used_block_id_;
   intptr_t context_level_;
   intptr_t try_index_;
   intptr_t catch_try_index_;
   intptr_t loop_depth_;
   GraphEntryInstr* graph_entry_;
 
   // The expression stack height.
   intptr_t temp_count_;
 
   // Outgoing argument stack height.
   intptr_t args_pushed_;
 
+  // A stack of enclosing nested statements.
+  NestedStatement* nesting_stack_;
+
   // The deopt id of the OSR entry or Isolate::kNoDeoptId if not compiling
   // for OSR.
   const intptr_t osr_id_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(FlowGraphBuilder);
 };
 
 
+// Base class for a stack of enclosing statements of interest (e.g.,
+// blocks (breakable) and loops (continuable)).
+class NestedStatement : public ValueObject {

[Florian Schneider, 2013/11/13 17:42:58]

Do you actually need to declare NestedStatement here? If a forward decl is
enough, you could move the declaration to the .cc file where the subclasses
already are.

[Kevin Millikin (Google), 2013/11/13 17:47:22]

It does look like a forward declaration is enough.  I'll move it.

+ public:
+  NestedStatement(FlowGraphBuilder* owner, const SourceLabel* label)
+      : owner_(owner),
+        label_(label),
+        outer_(owner->nesting_stack_),
+        break_target_(NULL) {
+    // Push on the owner's nesting stack.
+    owner->nesting_stack_ = this;
+  }
+
+  virtual ~NestedStatement() {
+    // Pop from the owner's nesting stack.
+    ASSERT(owner_->nesting_stack_ == this);
+    owner_->nesting_stack_ = outer_;
+  }
+
+  FlowGraphBuilder* owner() const { return owner_; }
+  const SourceLabel* label() const { return label_; }
+  NestedStatement* outer() const { return outer_; }
+  JoinEntryInstr* break_target() const { return break_target_; }
+
+  virtual JoinEntryInstr* BreakTargetFor(SourceLabel* label);
+  virtual JoinEntryInstr* ContinueTargetFor(SourceLabel* label);
+
+ private:
+  FlowGraphBuilder* owner_;
+  const SourceLabel* label_;
+  NestedStatement* outer_;
+
+  JoinEntryInstr* break_target_;
+};
+
+
 class TestGraphVisitor;
 
 // Translate an AstNode to a control-flow graph fragment for its effects
 // (e.g., a statement or an expression in an effect context).  Implements a
 // function from an AstNode and next temporary index to a graph fragment
 // with a single entry and at most one exit.  The fragment is represented by
 // an (entry, exit) pair of Instruction pointers:
 //
 //   - (NULL, NULL): an empty and open graph fragment
 //   - (i0, NULL): a closed graph fragment which has only non-local exits
@@ skipping 312 matching lines @@
   // Output parameters.
   GrowableArray<TargetEntryInstr**> true_successor_addresses_;
   GrowableArray<TargetEntryInstr**> false_successor_addresses_;
 
   intptr_t condition_token_pos_;
 };
 
 }  // namespace dart
 
 #endif  // VM_FLOW_GRAPH_BUILDER_H_