Add pass to remove empty blocks and recompute fall-through targets.

runtime/vm/flow_graph_compiler.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_COMPILER_H_
 #define VM_FLOW_GRAPH_COMPILER_H_
 
 #include "vm/allocation.h"
 #include "vm/assembler.h"
 #include "vm/code_descriptors.h"
@@ skipping 143 matching lines @@
   intptr_t count;
   CidTarget(intptr_t cid_arg,
             Function* target_arg,
             intptr_t count_arg)
       : cid(cid_arg), target(target_arg), count(count_arg) {}
 };
 
 
 class FlowGraphCompiler : public ValueObject {
  private:
-  struct BlockInfo : public ZoneAllocated {
+  class BlockInfo : public ZoneAllocated {
    public:
-    BlockInfo() : label() { }
-    Label label;
+    BlockInfo()
+        : jump_label_(&block_label_),
+          block_label_(),
+          fallthrough_label_(NULL),
+          is_marked_(false) {}
+
+    Label* jump_label() const { return jump_label_; }
+    void set_jump_label(Label* label) { jump_label_ = label; }
+
+    Label* fallthrough_label() const { return fallthrough_label_; }

[srdjan, 2013/03/08 19:02:31]

ASSERT that is not NULL?

[Vyacheslav Egorov (Google), 2013/03/08 19:04:23]

It can be NULL for the last block which has no fallthrough.

[srdjan, 2013/03/08 19:08:08]

Right. Maybe add a comment that it is NULL for blocks without fall-throughs..

[Vyacheslav Egorov (Google), 2013/03/08 19:10:11]

Done.

+    void set_fallthrough_label(Label* fallthrough_label) {
+      fallthrough_label_ = fallthrough_label;
+    }
+
+    bool WasCompacted() const {
+      return jump_label_ != &block_label_;
+    }
+
+    bool is_marked() const { return is_marked_; }
+    void mark() { is_marked_ = true; }
+
+   private:
+    Label* jump_label_;
+    Label block_label_;
+
+    Label* fallthrough_label_;
+
+    bool is_marked_;
   };
 
  public:
   FlowGraphCompiler(Assembler* assembler,
                     const FlowGraph& flow_graph,
                     bool is_optimizing);
 
   ~FlowGraphCompiler();
 
   static bool SupportsUnboxedMints();
@@ skipping 136 matching lines @@
   void EmitEqualityRegRegCompare(Register left,
                                  Register right,
                                  bool needs_number_check);
   // Implement equality: if any of the arguments is null do identity check.
   // Fallthrough calls super equality.
   void EmitSuperEqualityCallPrologue(Register result, Label* skip_call);
 
   intptr_t StackSize() const;
 
   // Returns assembler label associated with the given block entry.
-  Label* GetBlockLabel(BlockEntryInstr* block_entry) const;
+  Label* GetJumpLabel(BlockEntryInstr* block_entry) const;
+  bool WasCompacted(BlockEntryInstr* block_entry) const;
 
   // Returns true if there is a next block after the current one in
   // the block order and if it is the given block.
-  bool IsNextBlock(BlockEntryInstr* block_entry) const;
+  bool CanFallThroughTo(BlockEntryInstr* block_entry) const;
 
   void AddExceptionHandler(intptr_t try_index,
                            intptr_t outer_try_index,
                            intptr_t pc_offset,
                            const Array& handler_types);
   void AddCurrentDescriptor(PcDescriptors::Kind kind,
                             intptr_t deopt_id,
                             intptr_t token_pos);
 
   void RecordSafepoint(LocationSummary* locs);
@@ skipping 142 matching lines @@
   // block_order for reverse iterations.
   intptr_t reverse_index(intptr_t index) const {
     return block_order_.length() - index - 1;
   }
 
   // Returns 'sorted' array in decreasing count order.
   // The expected number of elements to sort is less than 10.
   static void SortICDataByCount(const ICData& ic_data,
                                 GrowableArray<CidTarget>* sorted);
 
+  void CompactBlock(BlockEntryInstr* block);
+  void CompactBlocks();
+

[srdjan, 2013/03/08 19:02:31]

Remove one line

[Vyacheslav Egorov (Google), 2013/03/08 19:04:23]

Done.

+
   class Assembler* assembler_;
   const ParsedFunction& parsed_function_;
   const GrowableArray<BlockEntryInstr*>& block_order_;
 
   // Compiler specific per-block state.  Indexed by postorder block number
   // for convenience.  This is not the block's index in the block order,
   // which is reverse postorder.
   BlockEntryInstr* current_block_;
   ExceptionHandlerList* exception_handlers_list_;
   DescriptorList* pc_descriptors_list_;
@@ skipping 16 matching lines @@
   // that should be used when deoptimizing we store it in this variable.
   // In future AddDeoptStub should be moved out of the instruction template.
   Environment* pending_deoptimization_env_;
 
   DISALLOW_COPY_AND_ASSIGN(FlowGraphCompiler);
 };
 
 }  // namespace dart
 
 #endif  // VM_FLOW_GRAPH_COMPILER_H_