Reland "[turbofan] Discard the shared code entry in the optimized code map."

src/objects.cc

 // 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.
 
 #include "src/objects.h"
 
 #include <cmath>
 #include <iomanip>
 #include <memory>
 #include <sstream>
@@ skipping 12117 matching lines @@
       LiteralsArray::New(isolate, feedback_vector, shared->num_literals());
   Handle<Code> code;
   if (result.code != nullptr) {
     code = Handle<Code>(result.code, isolate);
   }
   AddToOptimizedCodeMap(shared, native_context, code, literals,
                         BailoutId::None());
   return literals;
 }
 
-void SharedFunctionInfo::AddSharedCodeToOptimizedCodeMap(
-    Handle<SharedFunctionInfo> shared, Handle<Code> code) {
-  Isolate* isolate = shared->GetIsolate();
-  if (isolate->serializer_enabled()) return;
-  DCHECK(code->kind() == Code::OPTIMIZED_FUNCTION);
-  // Empty code maps are unsupported.
-  if (!shared->OptimizedCodeMapIsCleared()) {
-    Handle<WeakCell> cell = isolate->factory()->NewWeakCell(code);
-    // A collection may have occured and cleared the optimized code map in the
-    // allocation above.
-    if (!shared->OptimizedCodeMapIsCleared()) {
-      shared->optimized_code_map()->set(kSharedCodeIndex, *cell);
-    }
-  }
-}
-
 // static
 void SharedFunctionInfo::AddToOptimizedCodeMap(
     Handle<SharedFunctionInfo> shared, Handle<Context> native_context,
     MaybeHandle<Code> code, Handle<LiteralsArray> literals,
     BailoutId osr_ast_id) {
   Isolate* isolate = shared->GetIsolate();
   if (isolate->serializer_enabled()) return;
   DCHECK(code.is_null() ||
          code.ToHandleChecked()->kind() == Code::OPTIMIZED_FUNCTION);
   DCHECK(native_context->IsNativeContext());
   STATIC_ASSERT(kEntryLength == 4);
   Handle<FixedArray> new_code_map;
   int entry;
 
   if (shared->OptimizedCodeMapIsCleared()) {
     new_code_map = isolate->factory()->NewFixedArray(kInitialLength, TENURED);
-    new_code_map->set(kSharedCodeIndex, *isolate->factory()->empty_weak_cell(),
-                      SKIP_WRITE_BARRIER);
     entry = kEntriesStart;
   } else {
     Handle<FixedArray> old_code_map(shared->optimized_code_map(), isolate);
     entry = shared->SearchOptimizedCodeMapEntry(*native_context, osr_ast_id);
-    if (entry > kSharedCodeIndex) {
+    if (entry >= kEntriesStart) {
       // Just set the code and literals of the entry.
       if (!code.is_null()) {
         Handle<WeakCell> code_cell =
             isolate->factory()->NewWeakCell(code.ToHandleChecked());
         old_code_map->set(entry + kCachedCodeOffset, *code_cell);
       }
       Handle<WeakCell> literals_cell =
           isolate->factory()->NewWeakCell(literals);
       old_code_map->set(entry + kLiteralsOffset, *literals_cell);
       return;
@@ skipping 49 matching lines @@
 #endif
 
   FixedArray* old_code_map = shared->optimized_code_map();
   if (old_code_map != *new_code_map) {
     shared->set_optimized_code_map(*new_code_map);
   }
 }
 
 
 void SharedFunctionInfo::ClearOptimizedCodeMap() {
-  FixedArray* cleared_map = GetHeap()->cleared_optimized_code_map();
-  set_optimized_code_map(cleared_map, SKIP_WRITE_BARRIER);
+  FixedArray* empty_fixed_array = GetHeap()->empty_fixed_array();
+  set_optimized_code_map(empty_fixed_array, SKIP_WRITE_BARRIER);
 }
 
 
 void SharedFunctionInfo::EvictFromOptimizedCodeMap(Code* optimized_code,
                                                    const char* reason) {
   DisallowHeapAllocation no_gc;
   if (OptimizedCodeMapIsCleared()) return;
 
   Heap* heap = GetHeap();
   FixedArray* code_map = optimized_code_map();
@@ skipping 29 matching lines @@
       code_map->set(dst + kContextOffset, code_map->get(src + kContextOffset));
       code_map->set(dst + kCachedCodeOffset,
                     code_map->get(src + kCachedCodeOffset));
       code_map->set(dst + kLiteralsOffset,
                     code_map->get(src + kLiteralsOffset));
       code_map->set(dst + kOsrAstIdOffset,
                     code_map->get(src + kOsrAstIdOffset));
     }
     dst += kEntryLength;
   }
-  if (WeakCell::cast(code_map->get(kSharedCodeIndex))->value() ==
-      optimized_code) {
-    // Evict context-independent code as well.
-    code_map->set(kSharedCodeIndex, heap->empty_weak_cell(),
-                  SKIP_WRITE_BARRIER);
-    if (FLAG_trace_opt) {
-      PrintF("[evicting entry from optimizing code map (%s) for ", reason);
-      ShortPrint();
-      PrintF(" (context-independent code)]\n");
-    }
-  }
   if (dst != length) {
     // Always trim even when array is cleared because of heap verifier.
     heap->RightTrimFixedArray<Heap::CONCURRENT_TO_SWEEPER>(code_map,
                                                            length - dst);
-    if (code_map->length() == kEntriesStart &&
-        WeakCell::cast(code_map->get(kSharedCodeIndex))->cleared()) {
+    if (code_map->length() == kEntriesStart) {
       ClearOptimizedCodeMap();
     }
   }
 }
 
 
 void SharedFunctionInfo::TrimOptimizedCodeMap(int shrink_by) {
   FixedArray* code_map = optimized_code_map();
   DCHECK(shrink_by % kEntryLength == 0);
   DCHECK(shrink_by <= code_map->length() - kEntriesStart);
   // Always trim even when array is cleared because of heap verifier.
   GetHeap()->RightTrimFixedArray<Heap::SEQUENTIAL_TO_SWEEPER>(code_map,
                                                               shrink_by);
-  if (code_map->length() == kEntriesStart &&
-      WeakCell::cast(code_map->get(kSharedCodeIndex))->cleared()) {
+  if (code_map->length() == kEntriesStart) {
     ClearOptimizedCodeMap();
   }
 }
 
 // static
 void JSFunction::EnsureLiterals(Handle<JSFunction> function) {
   Handle<SharedFunctionInfo> shared(function->shared());
   Handle<Context> native_context(function->context()->native_context());
   if (function->literals() ==
       function->GetIsolate()->heap()->empty_literals_array()) {
@@ skipping 1492 matching lines @@
     FixedArray* optimized_code_map = this->optimized_code_map();
     int length = optimized_code_map->length();
     Smi* osr_ast_id_smi = Smi::FromInt(osr_ast_id.ToInt());
     for (int i = kEntriesStart; i < length; i += kEntryLength) {
       if (WeakCell::cast(optimized_code_map->get(i + kContextOffset))
                   ->value() == native_context &&
           optimized_code_map->get(i + kOsrAstIdOffset) == osr_ast_id_smi) {
         return i;
       }
     }
-    Object* shared_code =
-        WeakCell::cast(optimized_code_map->get(kSharedCodeIndex))->value();
-    if (shared_code->IsCode() && osr_ast_id.IsNone()) {
-      return kSharedCodeIndex;
-    }
   }
   return -1;
 }
 
 void SharedFunctionInfo::ClearCodeFromOptimizedCodeMap() {
   if (!OptimizedCodeMapIsCleared()) {
     FixedArray* optimized_code_map = this->optimized_code_map();
     int length = optimized_code_map->length();
     WeakCell* empty_weak_cell = GetHeap()->empty_weak_cell();
     for (int i = kEntriesStart; i < length; i += kEntryLength) {
       optimized_code_map->set(i + kCachedCodeOffset, empty_weak_cell,
                               SKIP_WRITE_BARRIER);
     }
-    optimized_code_map->set(kSharedCodeIndex, empty_weak_cell,
-                            SKIP_WRITE_BARRIER);
   }
 }
 
 CodeAndLiterals SharedFunctionInfo::SearchOptimizedCodeMap(
     Context* native_context, BailoutId osr_ast_id) {
   CodeAndLiterals result = {nullptr, nullptr};
   int entry = SearchOptimizedCodeMapEntry(native_context, osr_ast_id);
   if (entry != kNotFound) {
     FixedArray* code_map = optimized_code_map();
-    if (entry == kSharedCodeIndex) {
-      // We know the weak cell isn't cleared because we made sure of it in
-      // SearchOptimizedCodeMapEntry and performed no allocations since that
-      // call.
-      result = {
-          Code::cast(WeakCell::cast(code_map->get(kSharedCodeIndex))->value()),
-          nullptr};
-    } else {
-      DCHECK_LE(entry + kEntryLength, code_map->length());
-      WeakCell* cell = WeakCell::cast(code_map->get(entry + kCachedCodeOffset));
-      WeakCell* literals_cell =
-          WeakCell::cast(code_map->get(entry + kLiteralsOffset));
+    DCHECK_LE(entry + kEntryLength, code_map->length());
+    WeakCell* cell = WeakCell::cast(code_map->get(entry + kCachedCodeOffset));
+    WeakCell* literals_cell =
+        WeakCell::cast(code_map->get(entry + kLiteralsOffset));
 
-      result = {cell->cleared() ? nullptr : Code::cast(cell->value()),
-                literals_cell->cleared()
-                    ? nullptr
-                    : LiteralsArray::cast(literals_cell->value())};
-    }
+    result = {cell->cleared() ? nullptr : Code::cast(cell->value()),
+              literals_cell->cleared() ? nullptr : LiteralsArray::cast(
+                                                       literals_cell->value())};
   }
   return result;
 }
 
 
 #define DECLARE_TAG(ignore1, name, ignore2) name,
 const char* const VisitorSynchronization::kTags[
     VisitorSynchronization::kNumberOfSyncTags] = {
   VISITOR_SYNCHRONIZATION_TAGS_LIST(DECLARE_TAG)
 };
@@ skipping 6035 matching lines @@
   }
 
   // Evaluation of module body.
   Handle<JSFunction> resume(
       isolate->native_context()->generator_next_internal(), isolate);
   return Execution::Call(isolate, resume, generator, 0, nullptr);
 }
 
 }  // namespace internal
 }  // namespace v8