[ignition] Replace branch+loop analysis with a single pass

src/compiler/bytecode-analysis.h

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef V8_COMPILER_BYTECODE_LOOP_ANALYSIS_H_
-#define V8_COMPILER_BYTECODE_LOOP_ANALYSIS_H_
+#ifndef V8_COMPILER_BYTECODE_ANALYSIS_H_
+#define V8_COMPILER_BYTECODE_ANALYSIS_H_
 
 #include "src/handles.h"
 #include "src/zone/zone-containers.h"
 
 namespace v8 {
 namespace internal {
 
 class BytecodeArray;
 
 namespace compiler {
 
-class BytecodeBranchAnalysis;
-
-class BytecodeLoopAnalysis BASE_EMBEDDED {
+class BytecodeAnalysis BASE_EMBEDDED {
  public:
-  BytecodeLoopAnalysis(Handle<BytecodeArray> bytecode_array,
-                       const BytecodeBranchAnalysis* branch_analysis,
-                       Zone* zone);
+  BytecodeAnalysis(Handle<BytecodeArray> bytecode_array, Zone* zone);
 
   // Analyze the bytecodes to find the branch sites and their

[rmcilroy, 2016/11/22 11:02:07]

nit - this comment should be updated to talk about loops rather than branch
sites and targets.

[Leszek Swirski, 2016/11/22 17:39:03]

Done.

   // targets. No other methods in this class return valid information
   // until this has been called.
   void Analyze();
 
+  // Return true if the given offset is a loop header
+  bool IsLoopHeader(int offset) const;
   // Get the loop header offset of the containing loop for arbitrary
   // {offset}, or -1 if the {offset} is not inside any loop.
   int GetLoopOffsetFor(int offset) const;
   // Gets the loop header offset of the parent loop of the loop header
   // at {header_offset}, or -1 for outer-most loops.
   int GetParentLoopFor(int header_offset) const;
 
  private:
-  void AddLoopEntry(int entry_offset);
-  void AddBranch(int origin_offset, int target_offset);
+  void PushLoop(int loop_header, int loop_end);
 
   Zone* zone() const { return zone_; }
   Handle<BytecodeArray> bytecode_array() const { return bytecode_array_; }
 
   Handle<BytecodeArray> bytecode_array_;
-  const BytecodeBranchAnalysis* branch_analysis_;
   Zone* zone_;
 
-  int current_loop_offset_;
-  bool found_current_backedge_;
+  ZoneStack<int> loop_stack_;
 
-  // Map from the offset of a backedge jump to the offset of the corresponding
-  // loop header. There might be multiple backedges for do-while loops.
-  ZoneMap<int, int> backedge_to_header_;
-  // Map from the offset of a loop header to the offset of its parent's loop
-  // header. This map will have as many entries as there are loops in the
-  // function.
-  ZoneMap<int, int> loop_header_to_parent_;
+  ZoneMap<int, int> end_to_header_;
+  ZoneMap<int, int> header_to_parent_;
 
-  DISALLOW_COPY_AND_ASSIGN(BytecodeLoopAnalysis);
+  DISALLOW_COPY_AND_ASSIGN(BytecodeAnalysis);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
-#endif  // V8_COMPILER_BYTECODE_LOOP_ANALYSIS_H_
+#endif  // V8_COMPILER_BYTECODE_ANALYSIS_H_