[turbofan] Add and use bytecode loop assigment analysis

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_ANALYSIS_H_
 #define V8_COMPILER_BYTECODE_ANALYSIS_H_
 
 #include "src/base/hashmap.h"
 #include "src/bit-vector.h"
 #include "src/compiler/bytecode-liveness-map.h"
 #include "src/handles.h"
+#include "src/interpreter/bytecode-register.h"
 #include "src/zone/zone-containers.h"
 
 namespace v8 {
 namespace internal {
 
 class BytecodeArray;
 
 namespace compiler {
 
+class V8_EXPORT_PRIVATE BytecodeLoopAssignments {
+ public:
+  BytecodeLoopAssignments(int parameter_count, int register_count, Zone* zone);
+
+  void Add(interpreter::Register r);
+  void AddPair(interpreter::Register r);
+  void AddTriple(interpreter::Register r);
+  void AddAll();
+  void Union(const BytecodeLoopAssignments& other);
+
+  bool ContainsParameter(int index) const;
+  bool ContainsLocal(int index) const;
+  bool ContainsAccumulator() const;
+
+  int parameter_count() const { return parameter_count_; }
+  int local_count() const { return bit_vector_->length() - parameter_count_; }
+
+ private:
+  int parameter_count_;
+  BitVector* bit_vector_;
+};
+
+struct V8_EXPORT_PRIVATE LoopInfo {
+ public:
+  LoopInfo(int parent_offset, int parameter_count, int register_count,
+           Zone* zone)
+      : parent_offset_(parent_offset),
+        assignments_(parameter_count, register_count, zone) {}
+
+  int parent_offset() const { return parent_offset_; }
+
+  BytecodeLoopAssignments& assignments() { return assignments_; }
+  const BytecodeLoopAssignments& assignments() const { return assignments_; }
+
+ private:
+  // The offset to the parent loop, or -1 if there is no parent.
+  int parent_offset_;
+  BytecodeLoopAssignments assignments_;
+};
+
 class V8_EXPORT_PRIVATE BytecodeAnalysis BASE_EMBEDDED {
  public:
   BytecodeAnalysis(Handle<BytecodeArray> bytecode_array, Zone* zone,
                    bool do_liveness_analysis);
 
-  // Analyze the bytecodes to find the loop ranges and nesting. No other
-  // methods in this class return valid information until this has been called.
-  void Analyze();
+  // Analyze the bytecodes to find the loop ranges, loop nesting, loop
+  // assignments and liveness, under the assumption that there is an OSR bailout
+  // at {osr_bailout_id}.
+  //
+  // No other methods in this class return valid information until this has been
+  // called.
+  void Analyze(BailoutId osr_bailout_id);
 
   // 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;
+  // Get the loop info of the loop header at {header_offset}.
+  const LoopInfo& GetLoopInfoFor(int header_offset) const;
 
   // Gets the in-liveness for the bytecode at {offset}.
   const BytecodeLivenessState* GetInLivenessFor(int offset) const;
 
   // Gets the out-liveness for the bytecode at {offset}.
   const BytecodeLivenessState* GetOutLivenessFor(int offset) const;
 
   std::ostream& PrintLivenessTo(std::ostream& os) const;
 
  private:
+  struct LoopStackEntry {
+    int header_offset;
+    LoopInfo* loop_info;
+  };
+
   void PushLoop(int loop_header, int loop_end);
 
 #if DEBUG
   bool LivenessIsValid();
 #endif
 
   Zone* zone() const { return zone_; }
   Handle<BytecodeArray> bytecode_array() const { return bytecode_array_; }
 
  private:
   Handle<BytecodeArray> bytecode_array_;
   bool do_liveness_analysis_;
   Zone* zone_;
 
-  ZoneStack<int> loop_stack_;
+  ZoneStack<LoopStackEntry> loop_stack_;
   ZoneVector<int> loop_end_index_queue_;
 
   ZoneMap<int, int> end_to_header_;
-  ZoneMap<int, int> header_to_parent_;
+  ZoneMap<int, LoopInfo> header_to_info_;
 
   BytecodeLivenessMap liveness_map_;
 
   DISALLOW_COPY_AND_ASSIGN(BytecodeAnalysis);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_BYTECODE_ANALYSIS_H_