compilation-cache.cc.svn-base

Google浏览器V8内核代码

// Copyright 2008 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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//       with the distribution.
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//       contributors may be used to endorse or promote products derived
//       from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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#include "v8.h"

#include "compilation-cache.h"

namespace v8 { namespace internal {

enum {
  NUMBER_OF_ENTRY_KINDS = CompilationCache::EVAL_CONTEXTUAL + 1
};


// Keep separate tables for the different entry kinds.
static Object* tables[NUMBER_OF_ENTRY_KINDS] = { 0, };


static Handle<CompilationCacheTable> AllocateTable(int size) {
  CALL_HEAP_FUNCTION(CompilationCacheTable::Allocate(size),
                     CompilationCacheTable);
}


static Handle<CompilationCacheTable> GetTable(CompilationCache::Entry entry) {
  Handle<CompilationCacheTable> result;
  if (tables[entry]->IsUndefined()) {
    static const int kInitialCacheSize = 64;
    result = AllocateTable(kInitialCacheSize);
    tables[entry] = *result;
  } else {
    CompilationCacheTable* table = CompilationCacheTable::cast(tables[entry]);
    result = Handle<CompilationCacheTable>(table);
  }
  return result;
}


// We only re-use a cached function for some script source code if the
// script originates from the same places. This is to avoid issues
// when reporting errors, etc.
static bool HasOrigin(Handle<JSFunction> boilerplate,
                      Handle<Object> name,
                      int line_offset,
                      int column_offset) {
  Handle<Script> script =
      Handle<Script>(Script::cast(boilerplate->shared()->script()));
  // If the script name isn't set, the boilerplate script should have
  // an undefined name to have the same origin.
  if (name.is_null()) {
    return script->name()->IsUndefined();
  }
  // Do the fast bailout checks first.
  if (line_offset != script->line_offset()->value()) return false;
  if (column_offset != script->column_offset()->value()) return false;
  // Check that both names are strings. If not, no match.
  if (!name->IsString() || !script->name()->IsString()) return false;
  // Compare the two name strings for equality.
  return String::cast(*name)->Equals(String::cast(script->name()));
}


static Handle<JSFunction> Lookup(Handle<String> source,
                                 CompilationCache::Entry entry) {
  // Make sure not to leak the table into the surrounding handle
  // scope. Otherwise, we risk keeping old tables around even after
  // having cleared the cache.
  Object* result;
  { HandleScope scope;
    Handle<CompilationCacheTable> table = GetTable(entry);
    result = table->Lookup(*source);
  }
  if (result->IsJSFunction()) {
    return Handle<JSFunction>(JSFunction::cast(result));
  } else {
    return Handle<JSFunction>::null();
  }
}


Handle<JSFunction> CompilationCache::LookupScript(Handle<String> source,
                                                  Handle<Object> name,
                                                  int line_offset,
                                                  int column_offset) {
  Handle<JSFunction> result = Lookup(source, SCRIPT);
  if (result.is_null()) {
    Counters::compilation_cache_misses.Increment();
  } else if (HasOrigin(result, name, line_offset, column_offset)) {
    Counters::compilation_cache_hits.Increment();
  } else {
    result = Handle<JSFunction>::null();
    Counters::compilation_cache_misses.Increment();
  }
  return result;
}


Handle<JSFunction> CompilationCache::LookupEval(Handle<String> source,
                                                Entry entry) {
  ASSERT(entry == EVAL_GLOBAL || entry == EVAL_CONTEXTUAL);
  Handle<JSFunction> result = Lookup(source, entry);
  if (result.is_null()) {
    Counters::compilation_cache_misses.Increment();
  } else {
    Counters::compilation_cache_hits.Increment();
  }
  return result;
}


void CompilationCache::Associate(Handle<String> source,
                                 Entry entry,
                                 Handle<JSFunction> boilerplate) {
  HandleScope scope;
  ASSERT(boilerplate->IsBoilerplate());
  Handle<CompilationCacheTable> table = GetTable(entry);
  CALL_HEAP_FUNCTION_VOID(table->Put(*source, *boilerplate));
}


void CompilationCache::Clear() {
  for (int i = 0; i < NUMBER_OF_ENTRY_KINDS; i++) {
    tables[i] = Heap::undefined_value();
  }
}


void CompilationCache::Iterate(ObjectVisitor* v) {
  v->VisitPointers(&tables[0], &tables[NUMBER_OF_ENTRY_KINDS]);
}


} }  // namespace v8::internal