ARM microoptimizations to megamorphic stub probing.

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
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@@ skipping 4346 matching lines @@
   static const int kBinaryOpReturnTypeOffset = kBinaryOpTypeOffset + 1;
 
   static const int kAllowOSRAtLoopNestingLevelOffset = kFullCodeFlags + 1;
 
   static const int kSafepointTableOffsetOffset = kStackSlotsOffset + kIntSize;
   static const int kStackCheckTableOffsetOffset = kStackSlotsOffset + kIntSize;
 
   // Flags layout.  BitField<type, shift, size>.
   class ICStateField: public BitField<InlineCacheState, 0, 3> {};
   class TypeField: public BitField<PropertyType, 3, 4> {};
-  class KindField: public BitField<Kind, 7, 4> {};
-  class CacheHolderField: public BitField<InlineCacheHolderFlag, 11, 1> {};
+  class CacheHolderField: public BitField<InlineCacheHolderFlag, 7, 1> {};
+  class KindField: public BitField<Kind, 8, 4> {};
   class ExtraICStateField: public BitField<ExtraICState, 12, 2> {};
   class IsPregeneratedField: public BitField<bool, 14, 1> {};
 
   // Signed field cannot be encoded using the BitField class.
   static const int kArgumentsCountShift = 15;
   static const int kArgumentsCountMask = ~((1 << kArgumentsCountShift) - 1);
 
+  // This constant should be encodable in an ARM instruction.

[Michael Starzinger, 2012/02/02 13:14:20]

I think we need to have a static-assert at the usage site in stub-cache-arm.cc
where this is relevant. Otherwise that promise will be broken soon.

   static const int kFlagsNotUsedInLookup =
       TypeField::kMask | CacheHolderField::kMask;
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(Code);
 };
 
 
 // All heap objects have a Map that describes their structure.
 //  A Map contains information about:
@@ skipping 3857 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_