[TypeFeedbackVector] Root literal arrays in function literals slots

src/objects.h

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include <iosfwd>
 #include <memory>
 
@@ skipping 4990 matching lines @@
  public:
   static const int kVectorIndex = 0;
   static const int kFirstLiteralIndex = 1;
   V8_EXPORT_PRIVATE static const int kFeedbackVectorOffset;
   static const int kOffsetToFirstLiteral;
 
   static int OffsetOfLiteralAt(int index) {
     return OffsetOfElementAt(index + kFirstLiteralIndex);
   }
 
+  // Returns true if the vector isn't yet installed.
+  inline bool needs_feedback_vector() const;

[Michael Starzinger, 2017/01/11 12:07:27]

suggestion: Could we negate this predicate and call it "has_feedback_vector"
instead? The current naming makes it sound like the predicate is answering the
question whether this literals arrays "will ever need a feedback vector" whereas
it actually determines whether the literals array is "currently still missing"
one. WDYT?

[mvstanton, 2017/01/11 13:14:52]

Good idea, done.

   inline TypeFeedbackVector* feedback_vector() const;
   inline void set_feedback_vector(TypeFeedbackVector* vector);
+
   inline Object* literal(int literal_index) const;
   inline void set_literal(int literal_index, Object* literal);
   inline void set_literal_undefined(int literal_index);
   inline int literals_count() const;
 
   static Handle<LiteralsArray> New(Isolate* isolate,
                                    Handle<TypeFeedbackVector> vector,
                                    int number_of_literals,
                                    PretenureFlag pretenure = TENURED);
 
@@ skipping 2120 matching lines @@
   kTypedArrayEntries,
   kTypedArrayKeys,
   kTypedArrayLength,
   kTypedArrayValues,
   kSharedArrayBufferByteLength,
   kStringIterator,
   kStringIteratorNext,
 };
 
 
-// Result of searching in an optimized code map of a SharedFunctionInfo. Note
-// that both {code} and {literals} can be NULL to pass search result status.
-struct CodeAndLiterals {
-  Code* code;            // Cached optimized code.
-  LiteralsArray* literals;  // Cached literals array.
-};
-
-
 // SharedFunctionInfo describes the JSFunction information that can be
 // shared by multiple instances of the function.
 class SharedFunctionInfo: public HeapObject {
  public:
   // [name]: Function name.
   DECL_ACCESSORS(name, Object)
 
   // [code]: Function code.
   DECL_ACCESSORS(code, Code)
 
@@ skipping 10 matching lines @@
   inline bool IsInterpreted() const;
 
   inline void ReplaceCode(Code* code);
   inline bool HasBaselineCode() const;
 
   // [optimized_code_map]: Map from native context to optimized code
   // and a shared literals array.
   DECL_ACCESSORS(optimized_code_map, FixedArray)
 
   // Returns entry from optimized code map for specified context and OSR entry.
-  // Note that {code == nullptr, literals == nullptr} indicates no matching
-  // entry has been found, whereas {code, literals == nullptr} indicates that
-  // code is context-independent.
-  CodeAndLiterals SearchOptimizedCodeMap(Context* native_context,
-                                         BailoutId osr_ast_id);
+  Code* SearchOptimizedCodeMap(Context* native_context, BailoutId osr_ast_id);
 
   // Clear optimized code map.
   void ClearOptimizedCodeMap();
 
   // Like ClearOptimizedCodeMap, but preserves literals.
   void ClearCodeFromOptimizedCodeMap();
 
   // We have a special root FixedArray with the right shape and values
   // to represent the cleared optimized code map. This predicate checks
   // if that root is installed.
   inline bool OptimizedCodeMapIsCleared() const;
 
   // Removes a specific optimized code object from the optimized code map.
   // In case of non-OSR the code reference is cleared from the cache entry but
   // the entry itself is left in the map in order to proceed sharing literals.
   void EvictFromOptimizedCodeMap(Code* optimized_code, const char* reason);
 
   static Handle<LiteralsArray> FindOrCreateLiterals(
       Handle<SharedFunctionInfo> shared, Handle<Context> native_context);
 
   // Add or update entry in the optimized code map for context-dependent code.
   // If {code} is not given, then an existing entry's code won't be overwritten.
   static void AddToOptimizedCodeMap(Handle<SharedFunctionInfo> shared,
                                     Handle<Context> native_context,
                                     MaybeHandle<Code> code,

[Michael Starzinger, 2017/01/11 12:07:27]

Is there still a call-site left that does not pass a code? Otherwise we could
turn this into Handle<Code> instead and also drop the second sentence in the
comment above.

[mvstanton, 2017/01/11 13:14:52]

Good idea, done!

-                                    Handle<LiteralsArray> literals,
                                     BailoutId osr_ast_id);
 
   // Set up the link between shared function info and the script. The shared
   // function info is added to the list on the script.
   V8_EXPORT_PRIVATE static void SetScript(Handle<SharedFunctionInfo> shared,
                                           Handle<Object> script_object);
 
   // Layout description of the optimized code map.
   static const int kEntriesStart = 0;
   static const int kContextOffset = 0;
   static const int kCachedCodeOffset = 1;
-  static const int kLiteralsOffset = 2;
-  static const int kEntryLength = 3;
+  static const int kEntryLength = 2;
   static const int kInitialLength = kEntriesStart + kEntryLength;
 
   static const int kNotFound = -1;
 
   // Helpers for assembly code that does a backwards walk of the optimized code
   // map.
   static const int kOffsetToPreviousContext =
       FixedArray::kHeaderSize + kPointerSize * (kContextOffset - kEntryLength);
   static const int kOffsetToPreviousCachedCode =
       FixedArray::kHeaderSize +
       kPointerSize * (kCachedCodeOffset - kEntryLength);
-  static const int kOffsetToPreviousLiterals =
-      FixedArray::kHeaderSize + kPointerSize * (kLiteralsOffset - kEntryLength);
 
   // [scope_info]: Scope info.
   DECL_ACCESSORS(scope_info, ScopeInfo)
 
   // The outer scope info for the purpose of parsing this function, or the hole
   // value if it isn't yet known.
   DECL_ACCESSORS(outer_scope_info, HeapObject)
 
   // [construct stub]: Code stub for constructing instances of this function.
   DECL_ACCESSORS(construct_stub, Code)
@@ skipping 1118 matching lines @@
   static const int kSharedFunctionInfoOffset =
       kPrototypeOrInitialMapOffset + kPointerSize;
   static const int kContextOffset = kSharedFunctionInfoOffset + kPointerSize;
   static const int kLiteralsOffset = kContextOffset + kPointerSize;
   static const int kNonWeakFieldsEndOffset = kLiteralsOffset + kPointerSize;
   static const int kCodeEntryOffset = kNonWeakFieldsEndOffset;
   static const int kNextFunctionLinkOffset = kCodeEntryOffset + kPointerSize;
   static const int kSize = kNextFunctionLinkOffset + kPointerSize;
 
  private:
+  inline bool needs_literals_array() const;

[Michael Starzinger, 2017/01/11 12:07:27]

suggestion: Likewise, I propose changing to "has_literals_array". Also I would
be OK with making this public and moving it close to the {JSFunction::literals}
accessor.

[mvstanton, 2017/01/11 13:14:52]

Done.

+
   DISALLOW_IMPLICIT_CONSTRUCTORS(JSFunction);
 };
 
 
 // JSGlobalProxy's prototype must be a JSGlobalObject or null,
 // and the prototype is hidden. JSGlobalProxy always delegates
 // property accesses to its prototype if the prototype is not null.
 //
 // A JSGlobalProxy can be reinitialized which will preserve its identity.
 //
@@ skipping 3360 matching lines @@
   }
 };
 
 
 }  // NOLINT, false-positive due to second-order macros.
 }  // NOLINT, false-positive due to second-order macros.
 
 #include "src/objects/object-macros-undef.h"
 
 #endif  // V8_OBJECTS_H_