Remove redundant source position information in RelocInfo

src/assembler.h

Index: src/assembler.h
diff --git a/src/assembler.h b/src/assembler.h
index 2f2c73a9ce1ec419c9a2eaf652c94516d0645170..885fc7a9e909cad88befcccfbbc279af1980ed1f 100644
--- a/src/assembler.h
+++ b/src/assembler.h
@@ -644,14 +644,24 @@ class RelocInfo {
 // lower addresses.
 class RelocInfoWriter BASE_EMBEDDED {
  public:
-  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) {}
+  RelocInfoWriter()
+      : pos_(NULL),
+        last_pc_(NULL),
+        last_id_(0),
+        last_position_(0),
+        last_mode_(RelocInfo::NUMBER_OF_MODES),
+        next_position_candidate_pos_delta_(0),
+        next_position_candidate_pc_delta_(0),
+        next_position_candidate_flushed_(true) {}
+  RelocInfoWriter(byte* pos, byte* pc)
+      : pos_(pos),
+        last_pc_(pc),
+        last_id_(0),
+        last_position_(0),
+        last_mode_(RelocInfo::NUMBER_OF_MODES),
+        next_position_candidate_pos_delta_(0),
+        next_position_candidate_pc_delta_(0),
+        next_position_candidate_flushed_(true) {}
 
   byte* pos() const { return pos_; }
   byte* last_pc() const { return last_pc_; }
@@ -665,6 +675,8 @@ class RelocInfoWriter BASE_EMBEDDED {
     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.
@@ -681,11 +693,19 @@ class RelocInfoWriter BASE_EMBEDDED {
   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 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_;
+  uint32_t next_position_candidate_pc_delta_;
+  bool next_position_candidate_flushed_;
+
   DISALLOW_COPY_AND_ASSIGN(RelocInfoWriter);
 };