Change and simplify RelocInfo format.

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 331 matching lines @@
   // possible break locations. kNoPosition is used to indicate an
   // invalid/uninitialized position value.
   static const int kNoPosition = -1;
 
   // This string is used to add padding comments to the reloc info in cases
   // where we are not sure to have enough space for patching in during
   // lazy deoptimization. This is the case if we have indirect calls for which
   // we do not normally record relocation info.
   static const char* const kFillerCommentString;
 
   // The minimum size of a comment is equal to three bytes for the extra tagged

[Michael Starzinger, 2015/07/10 11:22:37]

nit: s/three/two/

   // pc + the tag for the data, and kPointerSize for the actual pointer to the
   // comment.
-  static const int kMinRelocCommentSize = 3 + kPointerSize;
+  static const int kMinRelocCommentSize = 2 + kPointerSize;
 
   // The maximum size for a call instruction including pc-jump.
   static const int kMaxCallSize = 6;
 
   // The maximum pc delta that will use the short encoding.
   static const int kMaxSmallPCDelta;
 
   enum Mode {
     // Please note the order is important (see IsCodeTarget, IsGCRelocMode).
     CODE_TARGET,  // Code target which is not any of the above.
@@ skipping 16 matching lines @@
     // Encoded internal reference, used only on MIPS, MIPS64 and PPC.
     INTERNAL_REFERENCE_ENCODED,
 
     // Marks constant and veneer pools. Only used on ARM and ARM64.
     // They use a custom noncompact encoding.
     CONST_POOL,
     VENEER_POOL,
 
     DEOPT_REASON,  // Deoptimization reason index.
 
-    // add more as needed
+    PC_JUMP,  // Used to encode long pc jumps.
+
     // Pseudo-types
-    NUMBER_OF_MODES,    // There are at most 15 modes with noncompact encoding.
+    NUMBER_OF_MODES,
     NONE32,             // never recorded 32-bit value
     NONE64,             // never recorded 64-bit value
     CODE_AGE_SEQUENCE,  // Not stored in RelocInfo array, used explictly by
                         // code aging.
 
     FIRST_REAL_RELOC_MODE = CODE_TARGET,
     LAST_REAL_RELOC_MODE = VENEER_POOL,
-    FIRST_PSEUDO_RELOC_MODE = CODE_AGE_SEQUENCE,
-    LAST_PSEUDO_RELOC_MODE = CODE_AGE_SEQUENCE,
     LAST_CODE_ENUM = DEBUG_BREAK,
     LAST_GCED_ENUM = CELL,
-    // Modes <= LAST_COMPACT_ENUM are guaranteed to have compact encoding.
-    LAST_COMPACT_ENUM = CODE_TARGET_WITH_ID,
-    LAST_STANDARD_NONCOMPACT_ENUM = INTERNAL_REFERENCE_ENCODED
   };
 
   RelocInfo() {}
 
   RelocInfo(byte* pc, Mode rmode, intptr_t data, Code* host)
       : pc_(pc), rmode_(rmode), data_(data), host_(host) {
   }
 
   static inline bool IsRealRelocMode(Mode mode) {
     return mode >= FIRST_REAL_RELOC_MODE &&
         mode <= LAST_REAL_RELOC_MODE;
   }
-  static inline bool IsPseudoRelocMode(Mode mode) {
-    DCHECK(!IsRealRelocMode(mode));
-    return mode >= FIRST_PSEUDO_RELOC_MODE &&
-        mode <= LAST_PSEUDO_RELOC_MODE;
-  }
   static inline bool IsConstructCall(Mode mode) {
     return mode == CONSTRUCT_CALL;
   }
   static inline bool IsCodeTarget(Mode mode) {
     return mode <= LAST_CODE_ENUM;
   }
   static inline bool IsEmbeddedObject(Mode mode) {
     return mode == EMBEDDED_OBJECT;
   }
   static inline bool IsCell(Mode mode) { return mode == CELL; }
@@ skipping 243 matching lines @@
   // 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;
   }
 
   void Finish() { FlushPosition(); }
 
   // 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;
+  // ExtraTag, VariableLengthPCJump, ExtraTag, pc_delta, data_delta.
+  // On ia32 and arm this is 1 + 4 + 1 + 1 + 4 = 11.
+  // On x64 this is 1 + 4 + 1 + 1 + 8 == 15;
   // Here we use the maximum of the two.
-  static const int kMaxSize = 16;
+  static const int kMaxSize = 15;
 
  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 WriteInt(int number);
-  inline void WriteDebugBreakSlotData(int data);
-  inline void WriteExtraTaggedIntData(int data_delta, int top_tag);
-  inline void WriteExtraTaggedPoolData(int data, int pool_type);
-  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);
+  inline uint32_t WriteLongPCJump(uint32_t pc_delta);
+
+  inline void WriteShortTaggedPC(uint32_t pc_delta, int tag);
+  inline void WriteShortTaggedData(intptr_t data_delta, int tag);
+
+  inline void WriteMode(RelocInfo::Mode rmode);
+  inline void WriteModeAndPC(uint32_t pc_delta, RelocInfo::Mode rmode);
+  inline void WriteIntData(int data_delta);
+  inline void WriteData(intptr_t data_delta);
   inline void WritePosition(int pc_delta, int pos_delta, RelocInfo::Mode rmode);
 
   void FlushPosition();
 
   byte* pos_;
   byte* last_pc_;
   int last_id_;
   int last_position_;
   RelocInfo::Mode last_mode_;
   int next_position_candidate_pos_delta_;
@@ skipping 30 matching lines @@
     DCHECK(!done());
     return &rinfo_;
   }
 
  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();
+  RelocInfo::Mode GetMode();
+
+  void AdvanceReadLongPCJump();
+
+  int GetShortDataTypeTag();
+  void ReadShortTaggedPC();
+  void ReadShortTaggedId();
+  void ReadShortTaggedPosition();
+  void ReadShortTaggedData();
+
   void AdvanceReadPC();
   void AdvanceReadId();
   void AdvanceReadInt();
-  void AdvanceReadPoolData();
-  void AdvanceReadDebugBreakSlotData();
   void AdvanceReadPosition();
   void AdvanceReadData();
-  void AdvanceReadVariableLengthPCJump();
-  int GetLocatableTypeTag();
-  void ReadTaggedId();
-  void ReadTaggedPosition();
-  void ReadTaggedData();
 
   // 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_;
   byte* code_age_sequence_;
@@ skipping 476 matching lines @@
   };
 
   Label emitted_label_;  // Records pc_offset of emitted pool
   PerTypeEntryInfo info_[ConstantPoolEntry::NUMBER_OF_TYPES];
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_ASSEMBLER_H_