src/objects/compilation-cache-table-inl.h

// Copyright 2017 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_COMPILATION_CACHE_TABLE_INL_H_
#define V8_OBJECTS_COMPILATION_CACHE_TABLE_INL_H_

#include "src/objects/compilation-cache-table.h"
#include "src/objects/name-inl.h"
#include "src/objects/script-inl.h"
#include "src/objects/shared-function-info.h"
#include "src/objects/smi.h"
#include "src/objects/string.h"

// Has to be the last include (doesn't have include guards):
#include "src/objects/object-macros.h"

namespace v8 {
namespace internal {

CompilationCacheTable::CompilationCacheTable(Address ptr)
    : HashTable<CompilationCacheTable, CompilationCacheShape>(ptr) {
  SLOW_DCHECK(IsCompilationCacheTable());
}

NEVER_READ_ONLY_SPACE_IMPL(CompilationCacheTable)
CAST_ACCESSOR(CompilationCacheTable)

Object CompilationCacheTable::PrimaryValueAt(InternalIndex entry) {
  return get(EntryToIndex(entry) + 1);
}

void CompilationCacheTable::SetPrimaryValueAt(InternalIndex entry, Object value,
                                              WriteBarrierMode mode) {
  set(EntryToIndex(entry) + 1, value, mode);
}

Object CompilationCacheTable::EvalFeedbackValueAt(InternalIndex entry) {
  static_assert(CompilationCacheShape::kEntrySize == 3);
  return get(EntryToIndex(entry) + 2);
}

void CompilationCacheTable::SetEvalFeedbackValueAt(InternalIndex entry,
                                                   Object value,
                                                   WriteBarrierMode mode) {
  set(EntryToIndex(entry) + 2, value, mode);
}

// The key in a script cache is a WeakFixedArray containing a weak pointer to
// the Script. The corresponding value can be either the root SharedFunctionInfo
// or undefined. The purpose of storing the root SharedFunctionInfo as the value
// is to keep it alive, not to save a lookup on the Script. A newly added entry
// always contains the root SharedFunctionInfo. After the root
// SharedFunctionInfo has aged sufficiently, it is replaced with undefined. In
// this way, all strong references to large objects are dropped, but there is
// still a way to get the Script if it happens to still be alive.
class ScriptCacheKey : public HashTableKey {
 public:
  enum Index {
    kHash,
    kWeakScript,
    kEnd,
  };

  ScriptCacheKey(Handle<String> source, const ScriptDetails* script_details,
                 Isolate* isolate);
  ScriptCacheKey(Handle<String> source, MaybeHandle<Object> name,
                 int line_offset, int column_offset,
                 v8::ScriptOriginOptions origin_options,
                 MaybeHandle<Object> host_defined_options, Isolate* isolate);

  bool IsMatch(Object other) override;
  bool MatchesOrigin(Script script);

  Handle<Object> AsHandle(Isolate* isolate, Handle<SharedFunctionInfo> shared);

  static base::Optional<String> SourceFromObject(Object obj) {
    DisallowGarbageCollection no_gc;
    DCHECK(obj.IsWeakFixedArray());
    WeakFixedArray array = WeakFixedArray::cast(obj);
    DCHECK_EQ(array.length(), kEnd);

    MaybeObject maybe_script = array.Get(kWeakScript);
    if (HeapObject script; maybe_script.GetHeapObjectIfWeak(&script)) {
      PrimitiveHeapObject source_or_undefined = Script::cast(script).source();
      // Scripts stored in the script cache should always have a source string.
      return String::cast(source_or_undefined);
    }

    DCHECK(maybe_script.IsCleared());
    return {};
  }

 private:
  Handle<String> source_;
  MaybeHandle<Object> name_;
  int line_offset_;
  int column_offset_;
  v8::ScriptOriginOptions origin_options_;
  MaybeHandle<Object> host_defined_options_;
  Isolate* isolate_;
};

uint32_t CompilationCacheShape::RegExpHash(String string, Smi flags) {
  return string.EnsureHash() + flags.value();
}

uint32_t CompilationCacheShape::EvalHash(String source,
                                         SharedFunctionInfo shared,
                                         LanguageMode language_mode,
                                         int position) {
  uint32_t hash = source.EnsureHash();
  if (shared.HasSourceCode()) {
    // Instead of using the SharedFunctionInfo pointer in the hash
    // code computation, we use a combination of the hash of the
    // script source code and the start position of the calling scope.
    // We do this to ensure that the cache entries can survive garbage
    // collection.
    Script script(Script::cast(shared.script()));
    hash ^= String::cast(script.source()).EnsureHash();
  }
  static_assert(LanguageModeSize == 2);
  if (is_strict(language_mode)) hash ^= 0x8000;
  hash += position;
  return hash;
}

uint32_t CompilationCacheShape::HashForObject(ReadOnlyRoots roots,
                                              Object object) {
  // Eval: The key field contains the hash as a Number.
  if (object.IsNumber()) return static_cast<uint32_t>(object.Number());

  // Code: The key field contains the SFI key.
  if (object.IsSharedFunctionInfo()) {
    return SharedFunctionInfo::cast(object).Hash();
  }

  // Script.
  if (object.IsWeakFixedArray()) {
    uint32_t result = static_cast<uint32_t>(Smi::ToInt(
        WeakFixedArray::cast(object).Get(ScriptCacheKey::kHash).ToSmi()));
    return result;
  }

  // Eval: See EvalCacheKey::ToHandle for the encoding.
  FixedArray val = FixedArray::cast(object);
  if (val.map() == roots.fixed_cow_array_map()) {
    DCHECK_EQ(4, val.length());
    String source = String::cast(val.get(1));
    int language_unchecked = Smi::ToInt(val.get(2));
    DCHECK(is_valid_language_mode(language_unchecked));
    LanguageMode language_mode = static_cast<LanguageMode>(language_unchecked);
    int position = Smi::ToInt(val.get(3));
    Object shared = val.get(0);
    return EvalHash(source, SharedFunctionInfo::cast(shared), language_mode,
                    position);
  }

  // RegExp: The key field (and the value field) contains the
  // JSRegExp::data fixed array.
  DCHECK_GE(val.length(), JSRegExp::kMinDataArrayLength);
  return RegExpHash(String::cast(val.get(JSRegExp::kSourceIndex)),
                    Smi::cast(val.get(JSRegExp::kFlagsIndex)));
}

InfoCellPair::InfoCellPair(Isolate* isolate, SharedFunctionInfo shared,
                           FeedbackCell feedback_cell)
    : is_compiled_scope_(!shared.is_null() ? shared.is_compiled_scope(isolate)
                                           : IsCompiledScope()),
      shared_(shared),
      feedback_cell_(feedback_cell) {}

}  // namespace internal
}  // namespace v8

#include "src/objects/object-macros-undef.h"

#endif  // V8_OBJECTS_COMPILATION_CACHE_TABLE_INL_H_