Revert several changes that caused performance regressions

This change reverts the following:

400b2cc2 Don't rescue old top-level SharedFunctionInfos
Reviewed on https://chromium-review.googlesource.com/c/v8/v8/+/3657472

16a7150b Reland "Disable recompilation of existing Scripts from
           Isolate compilation cache"
Reviewed on https://chromium-review.googlesource.com/c/v8/v8/+/3655011

2df4d58a Fix rehashing of script compilation cache
Reviewed on https://chromium-review.googlesource.com/c/v8/v8/+/3654413

c8848cf4 Refactor CompilationSubCache
Reviewed on https://chromium-review.googlesource.com/c/v8/v8/+/3629603

25072178 Improve Script reuse in isolate compilation cache, part 1
Reviewed on https://chromium-review.googlesource.com/c/v8/v8/+/3597106

Bug: v8:12808, chromium:1325566, chromium:1325567, chromium:1325601, chromium:1328671, chromium:1328672, chromium:1328678, chromium:1328811, chromium:1328810
Change-Id: I1d318dc172e5214166d3b15f19903186f4fe6024
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3664023Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80744}

src/codegen/compilation-cache.h

@@ -18,49 +18,78 @@ class Handle;
 class RootVisitor;
 struct ScriptDetails;
 
-// The compilation cache consists of several sub-caches: one each for evals and
-// scripts, which use this class as a base class, and a separate generational
-// sub-cache for RegExps. 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 CompilationCacheEvalOrScript {
+// 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:
-  explicit CompilationCacheEvalOrScript(Isolate* isolate) : isolate_(isolate) {}
+  CompilationSubCache(Isolate* isolate, int generations)
+      : isolate_(isolate), generations_(generations) {
+    DCHECK_LE(generations, kMaxGenerations);
+  }
+
+  static constexpr int kFirstGeneration = 0;
+  static constexpr int kMaxGenerations = 2;
+
+  // 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) {
+    DCHECK_LT(kFirstGeneration, generations_);
+    tables_[kFirstGeneration] = *value;
+  }
 
-  // Allocates the table if it didn't yet exist.
-  Handle<CompilationCacheTable> GetTable();
+  // Age the sub-cache by evicting the oldest generation and creating a new
+  // young generation.
+  virtual void Age() = 0;
 
   // GC support.
   void Iterate(RootVisitor* v);
 
-  // Clears this sub-cache evicting all its content.
+  // Clear this sub-cache evicting all its content.
   void Clear();
 
-  // Removes given shared function info from sub-cache.
+  // Remove given shared function info from sub-cache.
   void Remove(Handle<SharedFunctionInfo> function_info);
 
+  // Number of generations in this sub-cache.
+  int generations() const { return generations_; }
+
  protected:
   Isolate* isolate() const { return isolate_; }
 
+  // Ageing occurs either by removing the oldest generation, or with
+  // custom logic implemented in CompilationCacheTable::Age.
+  static void AgeByGeneration(CompilationSubCache* c);
+  static void AgeCustom(CompilationSubCache* c);
+
+ private:
   Isolate* const isolate_;
-  Object table_;
+  const int generations_;
+  Object tables_[kMaxGenerations];  // One for each generation.
 
-  DISALLOW_IMPLICIT_CONSTRUCTORS(CompilationCacheEvalOrScript);
+  DISALLOW_IMPLICIT_CONSTRUCTORS(CompilationSubCache);
 };
 
 // Sub-cache for scripts.
-class CompilationCacheScript : public CompilationCacheEvalOrScript {
+class CompilationCacheScript : public CompilationSubCache {
  public:
-  explicit CompilationCacheScript(Isolate* isolate)
-      : CompilationCacheEvalOrScript(isolate) {}
+  explicit CompilationCacheScript(Isolate* isolate);
 
-  using LookupResult = CompilationCacheScriptLookupResult;
-  LookupResult Lookup(Handle<String> source,
-                      const ScriptDetails& script_details);
+  MaybeHandle<SharedFunctionInfo> Lookup(Handle<String> source,
+                                         const ScriptDetails& script_details,
+                                         LanguageMode language_mode);
 
-  void Put(Handle<String> source, Handle<SharedFunctionInfo> function_info);
+  void Put(Handle<String> source, LanguageMode language_mode,
+           Handle<SharedFunctionInfo> function_info);
 
-  void Age();
+  void Age() override;
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(CompilationCacheScript);
@@ -78,10 +107,10 @@ class CompilationCacheScript : public CompilationCacheEvalOrScript {
 //    More specifically these are the CompileString, DebugEvaluate and
 //    DebugEvaluateGlobal runtime functions.
 // 4. The start position of the calling scope.
-class CompilationCacheEval : public CompilationCacheEvalOrScript {
+class CompilationCacheEval : public CompilationSubCache {
  public:
   explicit CompilationCacheEval(Isolate* isolate)
-      : CompilationCacheEvalOrScript(isolate) {}
+      : CompilationSubCache(isolate, 1) {}
 
   InfoCellPair Lookup(Handle<String> source,
                       Handle<SharedFunctionInfo> outer_info,
@@ -93,45 +122,26 @@ class CompilationCacheEval : public CompilationCacheEvalOrScript {
            Handle<Context> native_context, Handle<FeedbackCell> feedback_cell,
            int position);
 
-  void Age();
+  void Age() override;
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(CompilationCacheEval);
 };
 
 // Sub-cache for regular expressions.
-class CompilationCacheRegExp {
+class CompilationCacheRegExp : public CompilationSubCache {
  public:
-  CompilationCacheRegExp(Isolate* isolate) : isolate_(isolate) {}
+  CompilationCacheRegExp(Isolate* isolate, int generations)
+      : CompilationSubCache(isolate, generations) {}
 
   MaybeHandle<FixedArray> Lookup(Handle<String> source, JSRegExp::Flags flags);
 
   void Put(Handle<String> source, JSRegExp::Flags flags,
            Handle<FixedArray> data);
 
-  // The number of generations for the RegExp sub cache.
-  static const int kGenerations = 2;
-
-  // Gets the compilation cache tables for a specific generation. Allocates the
-  // table if it does not yet exist.
-  Handle<CompilationCacheTable> GetTable(int generation);
-
-  // Ages the sub-cache by evicting the oldest generation and creating a new
-  // young generation.
-  void Age();
-
-  // GC support.
-  void Iterate(RootVisitor* v);
-
-  // Clears this sub-cache evicting all its content.
-  void Clear();
+  void Age() override;
 
  private:
-  Isolate* isolate() const { return isolate_; }
-
-  Isolate* const isolate_;
-  Object tables_[kGenerations];  // One for each generation.
-
   DISALLOW_IMPLICIT_CONSTRUCTORS(CompilationCacheRegExp);
 };
 
@@ -144,10 +154,10 @@ class V8_EXPORT_PRIVATE CompilationCache {
   CompilationCache(const CompilationCache&) = delete;
   CompilationCache& operator=(const CompilationCache&) = delete;
 
-  // Finds the Script and root SharedFunctionInfo for a script source string.
-  // Returns empty handles if the cache doesn't contain a script for the given
-  // source string with the right origin.
-  CompilationCacheScript::LookupResult LookupScript(
+  // Finds the script shared function info for a source
+  // string. Returns an empty handle if the cache doesn't contain a
+  // script for the given source string with the right origin.
+  MaybeHandle<SharedFunctionInfo> LookupScript(
       Handle<String> source, const ScriptDetails& script_details,
       LanguageMode language_mode);
 
@@ -164,7 +174,7 @@ class V8_EXPORT_PRIVATE CompilationCache {
   MaybeHandle<FixedArray> LookupRegExp(Handle<String> source,
                                        JSRegExp::Flags flags);
 
-  // Associate the source string to the shared function
+  // Associate the (source, kind) pair to the shared function
   // info. This may overwrite an existing mapping.
   void PutScript(Handle<String> source, LanguageMode language_mode,
                  Handle<SharedFunctionInfo> function_info);
@@ -214,11 +224,6 @@ class V8_EXPORT_PRIVATE CompilationCache {
   bool IsEnabledScriptAndEval() const {
     return FLAG_compilation_cache && enabled_script_and_eval_;
   }
-  bool IsEnabledScript(LanguageMode language_mode) {
-    // Tests can change FLAG_use_strict at runtime. The compilation cache only
-    // contains scripts which were compiled with the default language mode.
-    return IsEnabledScriptAndEval() && language_mode == LanguageMode::kSloppy;
-  }
 
   Isolate* isolate() const { return isolate_; }
 
@@ -229,6 +234,9 @@ class V8_EXPORT_PRIVATE CompilationCache {
   CompilationCacheEval eval_contextual_;
   CompilationCacheRegExp reg_exp_;
 
+  static constexpr int kSubCacheCount = 4;
+  CompilationSubCache* subcaches_[kSubCacheCount];
+
   // Current enable state of the compilation cache for scripts and eval.
   bool enabled_script_and_eval_;
 

src/codegen/compiler.cc

@@ -1430,19 +1430,6 @@ Handle<SharedFunctionInfo> CreateTopLevelSharedFunctionInfo(
       parse_info->literal(), script, true);
 }
 
-Handle<SharedFunctionInfo> GetOrCreateTopLevelSharedFunctionInfo(
-    ParseInfo* parse_info, Handle<Script> script, Isolate* isolate) {
-  EnsureSharedFunctionInfosArrayOnScript(script, parse_info, isolate);
-  MaybeHandle<SharedFunctionInfo> maybe_shared =
-      Script::FindSharedFunctionInfo(script, isolate, parse_info->literal());
-  if (Handle<SharedFunctionInfo> shared; maybe_shared.ToHandle(&shared)) {
-    DCHECK_EQ(shared->function_literal_id(),
-              parse_info->literal()->function_literal_id());
-    return shared;
-  }
-  return CreateTopLevelSharedFunctionInfo(parse_info, script, isolate);
-}
-
 MaybeHandle<SharedFunctionInfo> CompileToplevel(
     ParseInfo* parse_info, Handle<Script> script,
     MaybeHandle<ScopeInfo> maybe_outer_scope_info, Isolate* isolate,
@@ -1476,7 +1463,7 @@ MaybeHandle<SharedFunctionInfo> CompileToplevel(
 
   // Create the SharedFunctionInfo and add it to the script's list.
   Handle<SharedFunctionInfo> shared_info =
-      GetOrCreateTopLevelSharedFunctionInfo(parse_info, script, isolate);
+      CreateTopLevelSharedFunctionInfo(parse_info, script, isolate);
 
   FinalizeUnoptimizedCompilationDataList
       finalize_unoptimized_compilation_data_list;
@@ -2819,22 +2806,17 @@ Handle<Script> NewScript(
 }
 
 MaybeHandle<SharedFunctionInfo> CompileScriptOnMainThread(
-    UnoptimizedCompileFlags flags, Handle<String> source,
+    const UnoptimizedCompileFlags flags, Handle<String> source,
     const ScriptDetails& script_details, NativesFlag natives,
     v8::Extension* extension, Isolate* isolate,
-    MaybeHandle<Script> maybe_script, IsCompiledScope* is_compiled_scope) {
-  Handle<Script> script;
-  if (maybe_script.ToHandle(&script)) {
-    flags.set_script_id(script->id());
-  }
+    IsCompiledScope* is_compiled_scope) {
   UnoptimizedCompileState compile_state;
   ReusableUnoptimizedCompileState reusable_state(isolate);
   ParseInfo parse_info(isolate, flags, &compile_state, &reusable_state);
   parse_info.set_extension(extension);
 
-  if (script.is_null()) {
-    script = NewScript(isolate, &parse_info, source, script_details, natives);
-  }
+  Handle<Script> script =
+      NewScript(isolate, &parse_info, source, script_details, natives);
   DCHECK_IMPLIES(parse_info.flags().collect_type_profile(),
                  script->IsUserJavaScript());
   DCHECK_EQ(parse_info.flags().is_repl_mode(), script->is_repl_mode());
@@ -2914,10 +2896,8 @@ bool CompilationExceptionIsRangeError(Isolate* isolate, Handle<Object> obj) {
 
 MaybeHandle<SharedFunctionInfo> CompileScriptOnBothBackgroundAndMainThread(
     Handle<String> source, const ScriptDetails& script_details,
-    MaybeHandle<Script> maybe_script, Isolate* isolate,
-    IsCompiledScope* is_compiled_scope) {
+    Isolate* isolate, IsCompiledScope* is_compiled_scope) {
   // Start a background thread compiling the script.
-  // TODO(v8:12808): Use maybe_script for the background compilation.
   StressBackgroundCompileThread background_compile_thread(
       isolate, source,
       script_details.origin_options.IsModule() ? ScriptType::kModule
@@ -2940,7 +2920,7 @@ MaybeHandle<SharedFunctionInfo> CompileScriptOnBothBackgroundAndMainThread(
     flags_copy.set_script_id(Script::kTemporaryScriptId);
     main_thread_maybe_result = CompileScriptOnMainThread(
         flags_copy, source, script_details, NOT_NATIVES_CODE, nullptr, isolate,
-        MaybeHandle<Script>(), &inner_is_compiled_scope);
+        &inner_is_compiled_scope);
     if (main_thread_maybe_result.is_null()) {
       // Assume all range errors are stack overflows.
       main_thread_had_stack_overflow = CompilationExceptionIsRangeError(
@@ -3031,7 +3011,6 @@ MaybeHandle<SharedFunctionInfo> GetSharedFunctionInfoForScriptImpl(
   const bool use_compilation_cache =
       extension == nullptr && script_details.repl_mode == REPLMode::kNo;
   MaybeHandle<SharedFunctionInfo> maybe_result;
-  MaybeHandle<Script> maybe_script;
   IsCompiledScope is_compiled_scope;
   if (use_compilation_cache) {
     bool can_consume_code_cache =
@@ -3041,13 +3020,8 @@ MaybeHandle<SharedFunctionInfo> GetSharedFunctionInfoForScriptImpl(
     }
 
     // First check per-isolate compilation cache.
-    CompilationCacheScript::LookupResult lookup_result =
+    maybe_result =
         compilation_cache->LookupScript(source, script_details, language_mode);
-    if (FLAG_isolate_script_cache_recompilation) {
-      maybe_script = lookup_result.script();
-    }
-    maybe_result = lookup_result.toplevel_sfi();
-    is_compiled_scope = lookup_result.is_compiled_scope();
     if (!maybe_result.is_null()) {
       compile_timer.set_hit_isolate_cache();
     } else if (can_consume_code_cache) {
@@ -3058,10 +3032,6 @@ MaybeHandle<SharedFunctionInfo> GetSharedFunctionInfoForScriptImpl(
       RCS_SCOPE(isolate, RuntimeCallCounterId::kCompileDeserialize);
       TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("v8.compile"),
                    "V8.CompileDeserialize");
-      // TODO(v8:12808): If a Script was found in the compilation cache, then
-      // both of the code paths below (Finish and Deserialize) should make use
-      // of that Script to avoid duplicating the Script itself or any
-      // preexisting SharedFunctionInfos.
       if (deserialize_task) {
         // If there's a cache consume task, finish it.
         maybe_result = deserialize_task->Finish(isolate, source,
@@ -3096,7 +3066,7 @@ MaybeHandle<SharedFunctionInfo> GetSharedFunctionInfoForScriptImpl(
       // If the --stress-background-compile flag is set, do the actual
       // compilation on a background thread, and wait for its result.
       maybe_result = CompileScriptOnBothBackgroundAndMainThread(
-          source, script_details, maybe_script, isolate, &is_compiled_scope);
+          source, script_details, isolate, &is_compiled_scope);
     } else {
       UnoptimizedCompileFlags flags =
           UnoptimizedCompileFlags::ForToplevelCompile(
@@ -3108,9 +3078,9 @@ MaybeHandle<SharedFunctionInfo> GetSharedFunctionInfoForScriptImpl(
 
       flags.set_is_eager(compile_options == ScriptCompiler::kEagerCompile);
 
-      maybe_result = CompileScriptOnMainThread(
-          flags, source, script_details, natives, extension, isolate,
-          maybe_script, &is_compiled_scope);
+      maybe_result =
+          CompileScriptOnMainThread(flags, source, script_details, natives,
+                                    extension, isolate, &is_compiled_scope);
     }
 
     // Add the result to the isolate cache.
@@ -3283,18 +3253,8 @@ Compiler::GetSharedFunctionInfoForStreamedScript(
   {
     TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("v8.compile"),
                  "V8.StreamingFinalization.CheckCache");
-    CompilationCacheScript::LookupResult lookup_result =
-        compilation_cache->LookupScript(source, script_details,
-                                        task->flags().outer_language_mode());
-
-    // TODO(v8:12808): Determine what to do if we finish streaming and find that
-    // another copy of the Script already exists but has no root
-    // SharedFunctionInfo or has an uncompiled SharedFunctionInfo. For now, we
-    // just ignore it and create a new Script.
-    if (!lookup_result.toplevel_sfi().is_null()) {
-      maybe_result = lookup_result.toplevel_sfi();
-    }
-
+    maybe_result = compilation_cache->LookupScript(
+        source, script_details, task->flags().outer_language_mode());
     if (!maybe_result.is_null()) {
       compile_timer.set_hit_isolate_cache();
     }
@@ -3315,8 +3275,6 @@ Compiler::GetSharedFunctionInfoForStreamedScript(
       // Add compiled code to the isolate cache.
       TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("v8.compile"),
                    "V8.StreamingFinalization.AddToCache");
-      DCHECK_EQ(task->flags().outer_language_mode(),
-                construct_language_mode(FLAG_use_strict));
       compilation_cache->PutScript(source, task->flags().outer_language_mode(),
                                    result);
     }

src/execution/isolate.cc

@@ -3887,12 +3887,6 @@ class BigIntPlatform : public bigint::Platform {
  private:
   Isolate* isolate_;
 };
-
-void MarkCompactPrologue(v8::Isolate* v8_isolate, v8::GCType gc_type,
-                         v8::GCCallbackFlags flags, void* data) {
-  Isolate* isolate = reinterpret_cast<i::Isolate*>(v8_isolate);
-  isolate->compilation_cache()->MarkCompactPrologue();
-}
 }  // namespace
 
 VirtualMemoryCage* Isolate::GetPtrComprCodeCageForTesting() {
@@ -4250,9 +4244,6 @@ bool Isolate::Init(SnapshotData* startup_snapshot_data,
   }
 #endif
 
-  heap()->AddGCPrologueCallback(MarkCompactPrologue, kGCTypeMarkSweepCompact,
-                                nullptr);
-
   initialized_ = true;
 
   return true;

src/execution/isolate.h

@@ -2055,6 +2055,11 @@ class V8_EXPORT_PRIVATE Isolate final : private HiddenFactory {
   static void SetIsolateThreadLocals(Isolate* isolate,
                                      PerIsolateThreadData* data);
 
+  void MarkCompactPrologue(bool is_compacting,
+                           ThreadLocalTop* archived_thread_data);
+  void MarkCompactEpilogue(bool is_compacting,
+                           ThreadLocalTop* archived_thread_data);
+
   void FillCache();
 
   // Propagate pending exception message to the v8::TryCatch.

src/flags/flag-definitions.h

@@ -965,9 +965,6 @@ DEFINE_BOOL(turbo_collect_feedback_in_generic_lowering, true,
             "enable experimental feedback collection in generic lowering.")
 DEFINE_BOOL(isolate_script_cache_ageing, true,
             "enable ageing of the isolate script cache.")
-DEFINE_BOOL(isolate_script_cache_recompilation, false,
-            "enable recompiling an existing Script from the Isolate cache when "
-            "there is not a compiled top-level SharedFunctionInfo")
 
 DEFINE_FLOAT(script_delay, 0, "busy wait [ms] on every Script::Run")
 DEFINE_FLOAT(script_delay_once, 0, "busy wait [ms] on the first Script::Run")

src/heap/heap.cc

@@ -2673,6 +2673,8 @@ void Heap::MarkCompactPrologue() {
   RegExpResultsCache::Clear(string_split_cache());
   RegExpResultsCache::Clear(regexp_multiple_cache());
 
+  isolate_->compilation_cache()->MarkCompactPrologue();
+
   FlushNumberStringCache();
 }
 

src/logging/counters-definitions.h

@@ -287,9 +287,6 @@ namespace internal {
   SC(alive_after_last_gc, V8.AliveAfterLastGC)            \
   SC(compilation_cache_hits, V8.CompilationCacheHits)     \
   SC(compilation_cache_misses, V8.CompilationCacheMisses) \
-  /* Number of times the cache contained a reusable Script but not   \
-     the root SharedFunctionInfo */                                  \
-  SC(compilation_cache_partial_hits, V8.CompilationCachePartialHits) \
   SC(objs_since_last_young, V8.ObjsSinceLastYoung)        \
   SC(objs_since_last_full, V8.ObjsSinceLastFull)
 

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

@@ -26,74 +26,11 @@ CompilationCacheTable::CompilationCacheTable(Address ptr)
 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,
-  };
-
-  explicit ScriptCacheKey(Handle<String> source);
-
-  bool IsMatch(Object other) override;
-
-  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_;
-};
-
 uint32_t CompilationCacheShape::RegExpHash(String string, Smi flags) {
   return string.EnsureHash() + flags.value();
 }
 
-uint32_t CompilationCacheShape::EvalHash(String source,
+uint32_t CompilationCacheShape::StringSharedHash(String source,
                                                  SharedFunctionInfo shared,
                                                  LanguageMode language_mode,
                                                  int position) {
@@ -113,6 +50,14 @@ uint32_t CompilationCacheShape::EvalHash(String source,
   return hash;
 }
 
+uint32_t CompilationCacheShape::StringSharedHash(String source,
+                                                 LanguageMode language_mode) {
+  uint32_t hash = source.EnsureHash();
+  static_assert(LanguageModeSize == 2);
+  if (is_strict(language_mode)) hash ^= 0x8000;
+  return hash;
+}
+
 uint32_t CompilationCacheShape::HashForObject(ReadOnlyRoots roots,
                                               Object object) {
   // Eval: The key field contains the hash as a Number.
@@ -123,24 +68,7 @@ uint32_t CompilationCacheShape::HashForObject(ReadOnlyRoots roots,
     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()));
-#ifdef DEBUG
-    base::Optional<String> script_key =
-        ScriptCacheKey::SourceFromObject(object);
-    if (script_key) {
-      uint32_t source_hash;
-      if (script_key->TryGetHash(&source_hash)) {
-        DCHECK_EQ(result, source_hash);
-      }
-    }
-#endif
-    return result;
-  }
-
-  // Eval: See EvalCacheKey::ToHandle for the encoding.
+  // Script: See StringSharedKey::ToHandle for the encoding.
   FixedArray val = FixedArray::cast(object);
   if (val.map() == roots.fixed_cow_array_map()) {
     DCHECK_EQ(4, val.length());
@@ -149,10 +77,14 @@ uint32_t CompilationCacheShape::HashForObject(ReadOnlyRoots roots,
     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);
-    DCHECK(shared.IsSharedFunctionInfo());
-    return EvalHash(source, SharedFunctionInfo::cast(shared), language_mode,
-                    position);
+    Object shared_or_smi = val.get(0);
+    if (shared_or_smi.IsSmi()) {
+      DCHECK_EQ(position, kNoSourcePosition);
+      return StringSharedHash(source, language_mode);
+    } else {
+      return StringSharedHash(source, SharedFunctionInfo::cast(shared_or_smi),
+                              language_mode, position);
+    }
   }
 
   // RegExp: The key field (and the value field) contains the

src/objects/compilation-cache-table.h

@@ -29,8 +29,13 @@ class CompilationCacheShape : public BaseShape<HashTableKey*> {
 
   static inline uint32_t RegExpHash(String string, Smi flags);
 
-  static inline uint32_t EvalHash(String source, SharedFunctionInfo shared,
-                                  LanguageMode language_mode, int position);
+  static inline uint32_t StringSharedHash(String source,
+                                          SharedFunctionInfo shared,
+                                          LanguageMode language_mode,
+                                          int position);
+
+  static inline uint32_t StringSharedHash(String source,
+                                          LanguageMode language_mode);
 
   static inline uint32_t HashForObject(ReadOnlyRoots roots, Object object);
 
@@ -74,34 +79,6 @@ class InfoCellPair {
   FeedbackCell feedback_cell_;
 };
 
-// A lookup result from the compilation cache for scripts. There are three
-// possible states:
-//
-// 1. Cache miss: script and toplevel_sfi are both null.
-// 2. Cache hit: script and toplevel_sfi are both non-null. toplevel_sfi is
-//    guaranteed to be compiled, and to stay compiled while this lookup result
-//    instance is alive.
-// 3. Partial cache hit: script is non-null, but toplevel_sfi is null. The
-//    script may contain an uncompiled toplevel SharedFunctionInfo.
-class CompilationCacheScriptLookupResult {
- public:
-  MaybeHandle<Script> script() const { return script_; }
-  MaybeHandle<SharedFunctionInfo> toplevel_sfi() const { return toplevel_sfi_; }
-  IsCompiledScope is_compiled_scope() const { return is_compiled_scope_; }
-
-  using RawObjects = std::pair<Script, SharedFunctionInfo>;
-
-  RawObjects GetRawObjects() const;
-
-  static CompilationCacheScriptLookupResult FromRawObjects(RawObjects raw,
-                                                           Isolate* isolate);
-
- private:
-  MaybeHandle<Script> script_;
-  MaybeHandle<SharedFunctionInfo> toplevel_sfi_;
-  IsCompiledScope is_compiled_scope_;
-};
-
 EXTERN_DECLARE_HASH_TABLE(CompilationCacheTable, CompilationCacheShape)
 
 class CompilationCacheTable
@@ -109,18 +86,14 @@ class CompilationCacheTable
  public:
   NEVER_READ_ONLY_SPACE
 
-  // The 'script' cache contains SharedFunctionInfos. Once a root
-  // SharedFunctionInfo has become old enough that its bytecode is flushed, the
-  // entry is still present and can be used to get the Script. For consistency,
-  // this function always returns the Script. Callers should check whether there
-  // is a root SharedFunctionInfo in the script and whether it is already
-  // compiled, and choose what to do accordingly.
-  static CompilationCacheScriptLookupResult LookupScript(
+  // The 'script' cache contains SharedFunctionInfos.
+  static MaybeHandle<SharedFunctionInfo> LookupScript(
       Handle<CompilationCacheTable> table, Handle<String> src,
-      Isolate* isolate);
+      LanguageMode language_mode, Isolate* isolate);
   static Handle<CompilationCacheTable> PutScript(
       Handle<CompilationCacheTable> cache, Handle<String> src,
-      Handle<SharedFunctionInfo> value, Isolate* isolate);
+      LanguageMode language_mode, Handle<SharedFunctionInfo> value,
+      Isolate* isolate);
 
   // Eval code only gets cached after a second probe for the
   // code object. To do so, on first "put" only a hash identifying the
@@ -151,24 +124,12 @@ class CompilationCacheTable
       JSRegExp::Flags flags, Handle<FixedArray> value);
 
   void Remove(Object value);
-  void RemoveEntry(InternalIndex entry);
-
-  inline Object PrimaryValueAt(InternalIndex entry);
-  inline void SetPrimaryValueAt(InternalIndex entry, Object value,
-                                WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
-  inline Object EvalFeedbackValueAt(InternalIndex entry);
-  inline void SetEvalFeedbackValueAt(
-      InternalIndex entry, Object value,
-      WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
-
-  // The initial placeholder insertion of the eval cache survives this many GCs.
-  static constexpr int kHashGenerations = 10;
+  void Age(Isolate* isolate);
 
   DECL_CAST(CompilationCacheTable)
 
  private:
-  static Handle<CompilationCacheTable> EnsureScriptTableCapacity(
-      Isolate* isolate, Handle<CompilationCacheTable> cache);
+  void RemoveEntry(int entry_index);
 
   OBJECT_CONSTRUCTORS(CompilationCacheTable,
                       HashTable<CompilationCacheTable, CompilationCacheShape>);

src/objects/hash-table-inl.h

@@ -238,12 +238,6 @@ Object HashTable<Derived, Shape>::KeyAt(PtrComprCageBase cage_base,
   return get(cage_base, EntryToIndex(entry) + kEntryKeyIndex, tag);
 }
 
-template <typename Derived, typename Shape>
-void HashTable<Derived, Shape>::SetKeyAt(InternalIndex entry, Object value,
-                                         WriteBarrierMode mode) {
-  set_key(EntryToIndex(entry), value, mode);
-}
-
 template <typename Derived, typename Shape>
 void HashTable<Derived, Shape>::set_key(int index, Object value) {
   DCHECK(!IsEphemeronHashTable());

src/objects/hash-table.h

@@ -165,9 +165,6 @@ class EXPORT_TEMPLATE_DECLARE(V8_EXPORT_PRIVATE) HashTable
   inline Object KeyAt(PtrComprCageBase cage_base, InternalIndex entry,
                       RelaxedLoadTag tag);
 
-  inline void SetKeyAt(InternalIndex entry, Object value,
-                       WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
-
   static const int kElementsStartIndex = kPrefixStartIndex + Shape::kPrefixSize;
   static const int kEntrySize = Shape::kEntrySize;
   static_assert(kEntrySize > 0);

test/cctest/test-api.cc

@@ -23855,25 +23855,23 @@ TEST(StreamingWithHarmonyScopes) {
   delete[] full_source;
 }
 
-namespace {
-void StreamingWithIsolateScriptCache(bool run_gc) {
-  i::FLAG_expose_gc = true;
+// Regression test for crbug.com/v8/12668. Verifies that after a streamed script
+// is inserted into the isolate script cache, a non-streamed script with
+// identical origin can reuse that data.
+TEST(StreamingWithIsolateScriptCache) {
   const char* chunks[] = {"'use strict'; (function test() { return 13; })",
                           nullptr};
   const char* full_source = chunks[0];
   v8::Isolate* isolate = CcTest::isolate();
-  auto i_isolate = reinterpret_cast<i::Isolate*>(isolate);
   v8::HandleScope scope(isolate);
   v8::ScriptOrigin origin(isolate, v8_str("http://foo.com"), 0, 0, false, -1,
                           v8::Local<v8::Value>(), false, false, false);
-  v8::Local<Value> first_function_untyped;
   i::Handle<i::JSFunction> first_function;
   i::Handle<i::JSFunction> second_function;
 
   // Run the script using streaming.
   {
     LocalContext env;
-    v8::EscapableHandleScope inner_scope(isolate);
 
     v8::ScriptCompiler::StreamedSource source(
         std::make_unique<TestSourceStream>(chunks),
@@ -23888,38 +23886,13 @@ void StreamingWithIsolateScriptCache(bool run_gc) {
                                     origin)
             .ToLocalChecked();
     v8::Local<Value> result(script->Run(env.local()).ToLocalChecked());
-    first_function_untyped = inner_scope.Escape(result);
-
-    if (run_gc) {
-      // Age the top-level bytecode for the script to encourage the Isolate
-      // script cache to evict it. However, there are still active Handles
-      // referring to functions in that script, so the script itself should stay
-      // alive and reachable via the Isolate script cache.
-      i::Handle<i::JSFunction> script_function =
-          i::Handle<i::JSFunction>::cast(v8::Utils::OpenHandle(*script));
-      i::Handle<i::BytecodeArray> script_bytecode(
-          script_function->shared().GetBytecodeArray(i_isolate), i_isolate);
-      for (int i = 0; i < 5; ++i) {
-        script_bytecode->MakeOlder();
-      }
-    }
+    first_function =
+        i::Handle<i::JSFunction>::cast(v8::Utils::OpenHandle(*result));
   }
 
-  first_function = i::Handle<i::JSFunction>::cast(
-      v8::Utils::OpenHandle(*first_function_untyped));
-
   // Run the same script in another Context without streaming.
   {
     LocalContext env;
-
-    if (run_gc) {
-      // Perform garbage collection, which should remove the top-level
-      // SharedFunctionInfo from the Isolate script cache. However, the
-      // corresponding Script is still reachable and therefore still present in
-      // the Isolate script cache.
-      CompileRun("gc();");
-    }
-
     v8::ScriptCompiler::Source script_source(v8_str(full_source), origin);
     Local<Script> script =
         v8::ScriptCompiler::Compile(env.local(), &script_source)
@@ -23933,32 +23906,6 @@ void StreamingWithIsolateScriptCache(bool run_gc) {
   // SharedFunctionInfo instance due to the isolate script cache.
   CHECK_EQ(first_function->shared(), second_function->shared());
 }
-}  // namespace
-
-// Regression test for crbug.com/v8/12668. Verifies that after a streamed script
-// is inserted into the isolate script cache, a non-streamed script with
-// identical origin can reuse that data.
-TEST(StreamingWithIsolateScriptCache) {
-  StreamingWithIsolateScriptCache(false);
-}
-
-// Variant of the above test which evicts the root SharedFunctionInfo from the
-// Isolate script cache but still reuses the same Script.
-TEST(StreamingWithIsolateScriptCacheClearingRootSFI) {
-  // TODO(v8:12808): Remove this check once background compilation is capable of
-  // reusing an existing Script.
-  if (v8::internal::FLAG_stress_background_compile) {
-    return;
-  }
-
-  // If the compiler is configured to not recompile a flushed root SFI, then
-  // this test is invalid.
-  if (!v8::internal::FLAG_isolate_script_cache_recompilation) {
-    return;
-  }
-
-  StreamingWithIsolateScriptCache(true);
-}
 
 TEST(CodeCache) {
   v8::Isolate::CreateParams create_params;

test/cctest/test-serialize.cc

@@ -1820,9 +1820,10 @@ TEST(CodeSerializerPromotedToCompilationCache) {
     ScriptDetails script_details(src);
     script_details.host_defined_options =
         default_script_details.host_defined_options;
-    auto lookup_result = isolate->compilation_cache()->LookupScript(
-        src, script_details, LanguageMode::kSloppy);
-    CHECK_EQ(*lookup_result.toplevel_sfi().ToHandleChecked(), *copy);
+    MaybeHandle<SharedFunctionInfo> shared =
+        isolate->compilation_cache()->LookupScript(src, script_details,
+                                                   LanguageMode::kSloppy);
+    CHECK_EQ(*shared.ToHandleChecked(), *copy);
   }
 
   {
@@ -1836,9 +1837,10 @@ TEST(CodeSerializerPromotedToCompilationCache) {
             default_host_defined_option_1_string);
     host_defined_options->set(1, *host_defined_option_1);
     script_details.host_defined_options = host_defined_options;
-    auto lookup_result = isolate->compilation_cache()->LookupScript(
-        src, script_details, LanguageMode::kSloppy);
-    CHECK_EQ(*lookup_result.toplevel_sfi().ToHandleChecked(), *copy);
+    MaybeHandle<SharedFunctionInfo> shared =
+        isolate->compilation_cache()->LookupScript(src, script_details,
+                                                   LanguageMode::kSloppy);
+    CHECK_EQ(*shared.ToHandleChecked(), *copy);
   }
 
   {
@@ -1847,48 +1849,49 @@ TEST(CodeSerializerPromotedToCompilationCache) {
         isolate->factory()->NewStringFromAsciiChecked(source));
     script_details.host_defined_options =
         default_script_details.host_defined_options;
-    auto lookup_result = isolate->compilation_cache()->LookupScript(
-        src, script_details, LanguageMode::kSloppy);
-    CHECK_EQ(*lookup_result.toplevel_sfi().ToHandleChecked(), *copy);
+    MaybeHandle<SharedFunctionInfo> shared =
+        isolate->compilation_cache()->LookupScript(src, script_details,
+                                                   LanguageMode::kSloppy);
+    CHECK_EQ(*shared.ToHandleChecked(), *copy);
   }
 
   {
     // Lookup with different name string should fail:
     ScriptDetails script_details(
         isolate->factory()->NewStringFromAsciiChecked("other"));
-    auto lookup_result = isolate->compilation_cache()->LookupScript(
-        src, script_details, LanguageMode::kSloppy);
-    CHECK(lookup_result.script().is_null() &&
-          lookup_result.toplevel_sfi().is_null());
+    MaybeHandle<SharedFunctionInfo> shared =
+        isolate->compilation_cache()->LookupScript(src, script_details,
+                                                   LanguageMode::kSloppy);
+    CHECK(shared.is_null());
   }
 
   {
     // Lookup with different position should fail:
     ScriptDetails script_details(src);
     script_details.line_offset = 0xFF;
-    auto lookup_result = isolate->compilation_cache()->LookupScript(
-        src, script_details, LanguageMode::kSloppy);
-    CHECK(lookup_result.script().is_null() &&
-          lookup_result.toplevel_sfi().is_null());
+    MaybeHandle<SharedFunctionInfo> shared =
+        isolate->compilation_cache()->LookupScript(src, script_details,
+                                                   LanguageMode::kSloppy);
+    CHECK(shared.is_null());
   }
 
   {
     // Lookup with different position should fail:
     ScriptDetails script_details(src);
     script_details.column_offset = 0xFF;
-    auto lookup_result = isolate->compilation_cache()->LookupScript(
-        src, script_details, LanguageMode::kSloppy);
-    CHECK(lookup_result.script().is_null() &&
-          lookup_result.toplevel_sfi().is_null());
+    MaybeHandle<SharedFunctionInfo> shared =
+        isolate->compilation_cache()->LookupScript(src, script_details,
+                                                   LanguageMode::kSloppy);
+    CHECK(shared.is_null());
   }
 
   {
     // Lookup with different language mode should fail:
     ScriptDetails script_details(src);
-    auto lookup_result = isolate->compilation_cache()->LookupScript(
-        src, script_details, LanguageMode::kStrict);
-    CHECK(lookup_result.script().is_null() &&
-          lookup_result.toplevel_sfi().is_null());
+    MaybeHandle<SharedFunctionInfo> shared =
+        isolate->compilation_cache()->LookupScript(src, script_details,
+                                                   LanguageMode::kStrict);
+    CHECK(shared.is_null());
   }
 
   {
@@ -1896,20 +1899,20 @@ TEST(CodeSerializerPromotedToCompilationCache) {
     ScriptOriginOptions origin_options(false, true);
     CHECK_NE(ScriptOriginOptions().Flags(), origin_options.Flags());
     ScriptDetails script_details(src, origin_options);
-    auto lookup_result = isolate->compilation_cache()->LookupScript(
-        src, script_details, LanguageMode::kSloppy);
-    CHECK(lookup_result.script().is_null() &&
-          lookup_result.toplevel_sfi().is_null());
+    MaybeHandle<SharedFunctionInfo> shared =
+        isolate->compilation_cache()->LookupScript(src, script_details,
+                                                   LanguageMode::kSloppy);
+    CHECK(shared.is_null());
   }
 
   {
     // Lookup with different host_defined_options should fail:
     ScriptDetails script_details(src);
     script_details.host_defined_options = isolate->factory()->NewFixedArray(5);
-    auto lookup_result = isolate->compilation_cache()->LookupScript(
-        src, script_details, LanguageMode::kSloppy);
-    CHECK(lookup_result.script().is_null() &&
-          lookup_result.toplevel_sfi().is_null());
+    MaybeHandle<SharedFunctionInfo> shared =
+        isolate->compilation_cache()->LookupScript(src, script_details,
+                                                   LanguageMode::kSloppy);
+    CHECK(shared.is_null());
   }
 
   delete cache;