Improve positions tracking inside the HGraphBuilder.

src/objects.h

 // Copyright 2012 the V8 project authors. 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.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
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@@ skipping 4920 matching lines @@
 //
 // It can be empty.
 class DeoptimizationInputData: public FixedArray {
  public:
   // Layout description.  Indices in the array.
   static const int kTranslationByteArrayIndex = 0;
   static const int kInlinedFunctionCountIndex = 1;
   static const int kLiteralArrayIndex = 2;
   static const int kOsrAstIdIndex = 3;
   static const int kOsrPcOffsetIndex = 4;
-  static const int kFirstDeoptEntryIndex = 5;
+  static const int kOptimizationIdIndex = 5;

[Vyacheslav Egorov (Chromium), 2014/01/29 16:41:36]

Rest of the change introduces no overhead unless FLAG_track_hydrogen_positions
is passed. This part however grows DeoptimizationInputData by one word to store
ID of the optimization.

In general DeoptimizationInputData is big and is also accompanied by a multiword
optimized code object so this overhead should not be noticable. 

However if we want to save space we can change encoding of this structure to be
more flexible. If we decide to pursue this as additional benefit of such action
we can remove OsrAstId and OsrPcOffset for many object (my guess they are not
used for many objects) and save 2 words.

+  static const int kFirstDeoptEntryIndex = 6;
 
   // Offsets of deopt entry elements relative to the start of the entry.
   static const int kAstIdRawOffset = 0;
   static const int kTranslationIndexOffset = 1;
   static const int kArgumentsStackHeightOffset = 2;
   static const int kPcOffset = 3;
   static const int kDeoptEntrySize = 4;
 
   // Simple element accessors.
 #define DEFINE_ELEMENT_ACCESSORS(name, type)      \
   type* name() {                                  \
     return type::cast(get(k##name##Index));       \
   }                                               \
   void Set##name(type* value) {                   \
     set(k##name##Index, value);                   \
   }
 
   DEFINE_ELEMENT_ACCESSORS(TranslationByteArray, ByteArray)
   DEFINE_ELEMENT_ACCESSORS(InlinedFunctionCount, Smi)
   DEFINE_ELEMENT_ACCESSORS(LiteralArray, FixedArray)
   DEFINE_ELEMENT_ACCESSORS(OsrAstId, Smi)
   DEFINE_ELEMENT_ACCESSORS(OsrPcOffset, Smi)
+  DEFINE_ELEMENT_ACCESSORS(OptimizationId, Smi)
 
 #undef DEFINE_ELEMENT_ACCESSORS
 
   // Accessors for elements of the ith deoptimization entry.
 #define DEFINE_ENTRY_ACCESSORS(name, type)                       \
   type* name(int i) {                                            \
     return type::cast(get(IndexForEntry(i) + k##name##Offset));  \
   }                                                              \
   void Set##name(int i, type* value) {                           \
     set(IndexForEntry(i) + k##name##Offset, value);              \
@@ skipping 5782 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_