RFC: Switch to ast ids (instead of positions) for type feedback.

src/assembler.h

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // All Rights Reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 // - Redistributions of source code must retain the above copyright notice,
 // this list of conditions and the following disclaimer.
 //
@@ skipping 160 matching lines @@
   // statement_position). The "position" is collected at places in the source
   // code which are of interest when making stack traces to pin-point the source
   // location of a stack frame as close as possible. The "statement position" is
   // collected at the beginning at each statement, and is used to indicate
   // possible break locations. kNoPosition is used to indicate an
   // invalid/uninitialized position value.
   static const int kNoPosition = -1;
 
   enum Mode {
     // Please note the order is important (see IsCodeTarget, IsGCRelocMode).
+    CODE_TARGET,  // Code target which is not any of the below.
+    CODE_TARGET_WITH_ID,
     CONSTRUCT_CALL,  // code target that is a call to a JavaScript constructor.
     CODE_TARGET_CONTEXT,  // Code target used for contextual loads.
     DEBUG_BREAK,  // Code target for the debugger statement.
-    CODE_TARGET,  // Code target which is not any of the above.
     EMBEDDED_OBJECT,
 
     GLOBAL_PROPERTY_CELL,
 
     // Everything after runtime_entry (inclusive) is not GC'ed.
     RUNTIME_ENTRY,
     JS_RETURN,  // Marks start of the ExitJSFrame code.
     COMMENT,
     POSITION,  // See comment for kNoPosition above.
     STATEMENT_POSITION,  // See comment for kNoPosition above.
     DEBUG_BREAK_SLOT,  // Additional code inserted for debug break slot.
     EXTERNAL_REFERENCE,  // The address of an external C++ function.
     INTERNAL_REFERENCE,  // An address inside the same function.
 
     // add more as needed
     // Pseudo-types
-    NUMBER_OF_MODES,  // must be no greater than 14 - see RelocInfoWriter
+    NUMBER_OF_MODES,  // must be no greater than ?? - see RelocInfoWriter

[fschneider, 2011/02/11 11:28:18]

Update comment. Maybe a STATIC_ASSERT would be better than just a comment or
normal ASSERT.

     NONE,  // never recorded
-    LAST_CODE_ENUM = CODE_TARGET,
-    LAST_GCED_ENUM = EMBEDDED_OBJECT
+    LAST_CODE_ENUM = DEBUG_BREAK,
+    LAST_GCED_ENUM = EMBEDDED_OBJECT,
+    // Modes <= LAST_COMPACT_ENUM are guaranteed to have compact
+    // encoding.
+    LAST_COMPACT_ENUM = CODE_TARGET_WITH_ID
   };
 
 
   RelocInfo() {}
   RelocInfo(byte* pc, Mode rmode, intptr_t data)
       : pc_(pc), rmode_(rmode), data_(data) {
   }
 
   static inline bool IsConstructCall(Mode mode) {
     return mode == CONSTRUCT_CALL;
@@ skipping 109 matching lines @@
   static const char* RelocModeName(Mode rmode);
   void Print();
 #endif  // ENABLE_DISASSEMBLER
 #ifdef DEBUG
   // Debugging
   void Verify();
 #endif
 
   static const int kCodeTargetMask = (1 << (LAST_CODE_ENUM + 1)) - 1;
   static const int kPositionMask = 1 << POSITION | 1 << STATEMENT_POSITION;
-  static const int kDebugMask = kPositionMask | 1 << COMMENT;
+  static const int kDataMask =
+      (1 << CODE_TARGET_WITH_ID) | kPositionMask | (1 << COMMENT);
   static const int kApplyMask;  // Modes affected by apply. Depends on arch.
 
  private:
   // On ARM, note that pc_ is the address of the constant pool entry
   // to be relocated and not the address of the instruction
   // referencing the constant pool entry (except when rmode_ ==
   // comment).
   byte* pc_;
   Mode rmode_;
   intptr_t data_;
   friend class RelocIterator;
 };
 
 
 // RelocInfoWriter serializes a stream of relocation info. It writes towards
 // lower addresses.
 class RelocInfoWriter BASE_EMBEDDED {
  public:
-  RelocInfoWriter() : pos_(NULL), last_pc_(NULL), last_data_(0) {}
-  RelocInfoWriter(byte* pos, byte* pc) : pos_(pos), last_pc_(pc),
-                                         last_data_(0) {}
+  RelocInfoWriter() : pos_(NULL),
+                      last_pc_(NULL),
+                      last_id_(0),
+                      last_position_(0) {}
+  RelocInfoWriter(byte* pos, byte* pc) : pos_(pos),
+                                         last_pc_(pc),
+                                         last_id_(0),
+                                         last_position_(0) {}
 
   byte* pos() const { return pos_; }
   byte* last_pc() const { return last_pc_; }
 
   void Write(const RelocInfo* rinfo);
 
   // Update the state of the stream after reloc info buffer
   // and/or code is moved while the stream is active.
   void Reposition(byte* pos, byte* pc) {
     pos_ = pos;
     last_pc_ = pc;
   }
 
   // Max size (bytes) of a written RelocInfo. Longest encoding is
   // ExtraTag, VariableLengthPCJump, ExtraTag, pc_delta, ExtraTag, data_delta.
   // On ia32 and arm this is 1 + 4 + 1 + 1 + 1 + 4 = 12.
   // On x64 this is 1 + 4 + 1 + 1 + 1 + 8 == 16;
   // Here we use the maximum of the two.
   static const int kMaxSize = 16;
 
  private:
   inline uint32_t WriteVariableLengthPCJump(uint32_t pc_delta);
   inline void WriteTaggedPC(uint32_t pc_delta, int tag);
   inline void WriteExtraTaggedPC(uint32_t pc_delta, int extra_tag);
+  inline void WriteExtraTaggedIntData(int data_delta, int top_tag);
   inline void WriteExtraTaggedData(intptr_t data_delta, int top_tag);
   inline void WriteTaggedData(intptr_t data_delta, int tag);
   inline void WriteExtraTag(int extra_tag, int top_tag);
 
   byte* pos_;
   byte* last_pc_;
-  intptr_t last_data_;
+  int last_id_;
+  int last_position_;
   DISALLOW_COPY_AND_ASSIGN(RelocInfoWriter);
 };
 
 
 // A RelocIterator iterates over relocation information.
 // Typical use:
 //
 //   for (RelocIterator it(code); !it.done(); it.next()) {
 //     // do something with it.rinfo() here
 //   }
@@ skipping 21 matching lines @@
  private:
   // Advance* moves the position before/after reading.
   // *Read* reads from current byte(s) into rinfo_.
   // *Get* just reads and returns info on current byte.
   void Advance(int bytes = 1) { pos_ -= bytes; }
   int AdvanceGetTag();
   int GetExtraTag();
   int GetTopTag();
   void ReadTaggedPC();
   void AdvanceReadPC();
+  void AdvanceReadId();
+  void AdvanceReadPosition();
   void AdvanceReadData();
   void AdvanceReadVariableLengthPCJump();
-  int GetPositionTypeTag();
-  void ReadTaggedData();
-
-  static RelocInfo::Mode DebugInfoModeFromTag(int tag);
+  int GetLocatableTypeTag();
+  void ReadTaggedId();
+  void ReadTaggedPosition();
 
   // If the given mode is wanted, set it in rinfo_ and return true.
   // Else return false. Used for efficiently skipping unwanted modes.
   bool SetMode(RelocInfo::Mode mode) {
     return (mode_mask_ & (1 << mode)) ? (rinfo_.rmode_ = mode, true) : false;
   }
 
   byte* pos_;
   byte* end_;
   RelocInfo rinfo_;
   bool done_;
   int mode_mask_;
+  int last_id_;
+  int last_position_;
   DISALLOW_COPY_AND_ASSIGN(RelocIterator);
 };
 
 
 //------------------------------------------------------------------------------
 // External function
 
 //----------------------------------------------------------------------------
 class IC_Utility;
 class SCTableReference;
@@ skipping 258 matching lines @@
   return num_bits_set;
 }
 
 // Computes pow(x, y) with the special cases in the spec for Math.pow.
 double power_double_int(double x, int y);
 double power_double_double(double x, double y);
 
 } }  // namespace v8::internal
 
 #endif  // V8_ASSEMBLER_H_