compilation-cache.h 8.3 KB
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// Copyright 2012 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
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#ifndef V8_COMPILATION_CACHE_H_
#define V8_COMPILATION_CACHE_H_

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namespace v8 {
namespace internal {
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// The compilation cache consists of several generational sub-caches which uses
// this class as a base class. A sub-cache contains a compilation cache tables
// for each generation of the sub-cache. Since the same source code string has
// different compiled code for scripts and evals, we use separate sub-caches
// for different compilation modes, to avoid retrieving the wrong result.
class CompilationSubCache {
 public:
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  CompilationSubCache(Isolate* isolate, int generations)
      : isolate_(isolate),
        generations_(generations) {
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    tables_ = NewArray<Object*>(generations);
  }

  ~CompilationSubCache() { DeleteArray(tables_); }

  // Index for the first generation in the cache.
  static const int kFirstGeneration = 0;

  // Get the compilation cache tables for a specific generation.
  Handle<CompilationCacheTable> GetTable(int generation);

  // Accessors for first generation.
  Handle<CompilationCacheTable> GetFirstTable() {
    return GetTable(kFirstGeneration);
  }
  void SetFirstTable(Handle<CompilationCacheTable> value) {
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    DCHECK(kFirstGeneration < generations_);
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    tables_[kFirstGeneration] = *value;
  }

  // Age the sub-cache by evicting the oldest generation and creating a new
  // young generation.
  void Age();

  // GC support.
  void Iterate(ObjectVisitor* v);
  void IterateFunctions(ObjectVisitor* v);

  // Clear this sub-cache evicting all its content.
  void Clear();

  // Remove given shared function info from sub-cache.
  void Remove(Handle<SharedFunctionInfo> function_info);

  // Number of generations in this sub-cache.
  inline int generations() { return generations_; }

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 protected:
  Isolate* isolate() { return isolate_; }

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 private:
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  Isolate* isolate_;
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  int generations_;  // Number of generations.
  Object** tables_;  // Compilation cache tables - one for each generation.

  DISALLOW_IMPLICIT_CONSTRUCTORS(CompilationSubCache);
};


// Sub-cache for scripts.
class CompilationCacheScript : public CompilationSubCache {
 public:
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  CompilationCacheScript(Isolate* isolate, int generations);
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  Handle<SharedFunctionInfo> Lookup(Handle<String> source,
                                    Handle<Object> name,
                                    int line_offset,
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                                    int column_offset,
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                                    bool is_shared_cross_origin,
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                                    Handle<Context> context);
  void Put(Handle<String> source,
           Handle<Context> context,
           Handle<SharedFunctionInfo> function_info);
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 private:
  bool HasOrigin(Handle<SharedFunctionInfo> function_info,
                 Handle<Object> name,
                 int line_offset,
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                 int column_offset,
                 bool is_shared_cross_origin);
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  void* script_histogram_;
  bool script_histogram_initialized_;

  DISALLOW_IMPLICIT_CONSTRUCTORS(CompilationCacheScript);
};


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// Sub-cache for eval scripts. Two caches for eval are used. One for eval calls
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// in native contexts and one for eval calls in other contexts. The cache
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// considers the following pieces of information when checking for matching
// entries:
// 1. The source string.
// 2. The shared function info of the calling function.
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// 3. Whether the source should be compiled as strict code or as sloppy code.
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//    Note: Currently there are clients of CompileEval that always compile
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//    sloppy code even if the calling function is a strict mode function.
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//    More specifically these are the CompileString, DebugEvaluate and
//    DebugEvaluateGlobal runtime functions.
// 4. The start position of the calling scope.
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class CompilationCacheEval: public CompilationSubCache {
 public:
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  CompilationCacheEval(Isolate* isolate, int generations)
      : CompilationSubCache(isolate, generations) { }
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  MaybeHandle<SharedFunctionInfo> Lookup(Handle<String> source,
                                         Handle<Context> context,
                                         StrictMode strict_mode,
                                         int scope_position);
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  void Put(Handle<String> source,
           Handle<Context> context,
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           Handle<SharedFunctionInfo> function_info,
           int scope_position);
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 private:
  DISALLOW_IMPLICIT_CONSTRUCTORS(CompilationCacheEval);
};


// Sub-cache for regular expressions.
class CompilationCacheRegExp: public CompilationSubCache {
 public:
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  CompilationCacheRegExp(Isolate* isolate, int generations)
      : CompilationSubCache(isolate, generations) { }
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  MaybeHandle<FixedArray> Lookup(Handle<String> source, JSRegExp::Flags flags);
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  void Put(Handle<String> source,
           JSRegExp::Flags flags,
           Handle<FixedArray> data);
 private:
  DISALLOW_IMPLICIT_CONSTRUCTORS(CompilationCacheRegExp);
};

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// The compilation cache keeps shared function infos for compiled
// scripts and evals. The shared function infos are looked up using
// the source string as the key. For regular expressions the
// compilation data is cached.
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class CompilationCache {
 public:
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  // Finds the script shared function info for a source
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  // string. Returns an empty handle if the cache doesn't contain a
  // script for the given source string with the right origin.
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  MaybeHandle<SharedFunctionInfo> LookupScript(
      Handle<String> source, Handle<Object> name, int line_offset,
      int column_offset, bool is_shared_cross_origin, Handle<Context> context);
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  // Finds the shared function info for a source string for eval in a
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  // given context.  Returns an empty handle if the cache doesn't
  // contain a script for the given source string.
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  MaybeHandle<SharedFunctionInfo> LookupEval(
      Handle<String> source, Handle<Context> context, StrictMode strict_mode,
      int scope_position);
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  // Returns the regexp data associated with the given regexp if it
  // is in cache, otherwise an empty handle.
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  MaybeHandle<FixedArray> LookupRegExp(
      Handle<String> source, JSRegExp::Flags flags);
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  // Associate the (source, kind) pair to the shared function
  // info. This may overwrite an existing mapping.
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  void PutScript(Handle<String> source,
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                 Handle<Context> context,
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                 Handle<SharedFunctionInfo> function_info);
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  // Associate the (source, context->closure()->shared(), kind) triple
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  // with the shared function info. This may overwrite an existing mapping.
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  void PutEval(Handle<String> source,
               Handle<Context> context,
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               Handle<SharedFunctionInfo> function_info,
               int scope_position);
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  // Associate the (source, flags) pair to the given regexp data.
  // This may overwrite an existing mapping.
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  void PutRegExp(Handle<String> source,
                 JSRegExp::Flags flags,
                 Handle<FixedArray> data);
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  // Clear the cache - also used to initialize the cache at startup.
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  void Clear();
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  // Remove given shared function info from all caches.
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  void Remove(Handle<SharedFunctionInfo> function_info);
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  // GC support.
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  void Iterate(ObjectVisitor* v);
  void IterateFunctions(ObjectVisitor* v);
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  // Notify the cache that a mark-sweep garbage collection is about to
  // take place. This is used to retire entries from the cache to
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  // avoid keeping them alive too long without using them.
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  void MarkCompactPrologue();
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  // Enable/disable compilation cache. Used by debugger to disable compilation
  // cache during debugging to make sure new scripts are always compiled.
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  void Enable();
  void Disable();
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 private:
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  explicit CompilationCache(Isolate* isolate);
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  ~CompilationCache();

  HashMap* EagerOptimizingSet();

  // The number of sub caches covering the different types to cache.
  static const int kSubCacheCount = 4;

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  bool IsEnabled() { return FLAG_compilation_cache && enabled_; }

  Isolate* isolate() { return isolate_; }

  Isolate* isolate_;

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  CompilationCacheScript script_;
  CompilationCacheEval eval_global_;
  CompilationCacheEval eval_contextual_;
  CompilationCacheRegExp reg_exp_;
  CompilationSubCache* subcaches_[kSubCacheCount];

  // Current enable state of the compilation cache.
  bool enabled_;

  friend class Isolate;

  DISALLOW_COPY_AND_ASSIGN(CompilationCache);
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};


} }  // namespace v8::internal

#endif  // V8_COMPILATION_CACHE_H_