[stubs] Generalize loop handling in CodeStubAssembler and improve common loop performance

src/code-stubs.cc

 // Copyright 2012 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/code-stubs.h"
 
 #include <sstream>
 
 #include "src/ast/ast.h"
 #include "src/bootstrapper.h"
@@ skipping 5161 matching lines @@
 
 void FastNewClosureStub::GenerateAssembly(CodeStubAssembler* assembler) const {
   assembler->Return(
       Generate(assembler, assembler->Parameter(0), assembler->Parameter(1)));
 }
 
 // static
 compiler::Node* FastNewFunctionContextStub::Generate(
     CodeStubAssembler* assembler, compiler::Node* function,
     compiler::Node* slots, compiler::Node* context) {
-  typedef CodeStubAssembler::Label Label;
   typedef compiler::Node Node;
-  typedef CodeStubAssembler::Variable Variable;
 
   Node* min_context_slots =
       assembler->Int32Constant(Context::MIN_CONTEXT_SLOTS);
   Node* length = assembler->Int32Add(slots, min_context_slots);
   Node* size = assembler->Int32Add(
       assembler->Word32Shl(length, assembler->Int32Constant(kPointerSizeLog2)),
       assembler->Int32Constant(FixedArray::kHeaderSize));
 
   // Create a new closure from the given function info in new space
   Node* function_context = assembler->Allocate(size);
@@ skipping 18 matching lines @@
       assembler->TheHoleConstant(), SKIP_WRITE_BARRIER);
 
   // Copy the native context from the previous context.
   Node* native_context = assembler->LoadNativeContext(context);
   assembler->StoreFixedArrayElement(
       function_context, assembler->Int32Constant(Context::NATIVE_CONTEXT_INDEX),
       native_context, SKIP_WRITE_BARRIER);
 
   // Initialize the rest of the slots to undefined.
   Node* undefined = assembler->UndefinedConstant();
-  Variable var_slot_index(assembler, MachineRepresentation::kWord32);
-  var_slot_index.Bind(min_context_slots);
-  Label loop(assembler, &var_slot_index), after_loop(assembler);
-  assembler->Goto(&loop);
-
-  assembler->Bind(&loop);
-  {
-    Node* slot_index = var_slot_index.value();
-    assembler->GotoUnless(assembler->Int32LessThan(slot_index, length),
-                          &after_loop);
-    assembler->StoreFixedArrayElement(function_context, slot_index, undefined,
-                                      SKIP_WRITE_BARRIER);
-    Node* one = assembler->Int32Constant(1);
-    Node* next_index = assembler->Int32Add(slot_index, one);
-    var_slot_index.Bind(next_index);
-    assembler->Goto(&loop);
-  }
-  assembler->Bind(&after_loop);
+  assembler->BuildFastFixedArrayForEach(
+      function_context, FAST_ELEMENTS, min_context_slots, length,
+      [undefined](CodeStubAssembler* assembler, Node* context, Node* offset) {
+        assembler->StoreNoWriteBarrier(MachineType::PointerRepresentation(),
+                                       context, offset, undefined);
+      });
 
   return function_context;
 }
 
 void FastNewFunctionContextStub::GenerateAssembly(
     CodeStubAssembler* assembler) const {
   typedef compiler::Node Node;
   Node* function = assembler->Parameter(Descriptor::kFunction);
   Node* slots = assembler->Parameter(FastNewFunctionContextDescriptor::kSlots);
   Node* context = assembler->Parameter(Descriptor::kContext);
@@ skipping 621 matching lines @@
 
   if (type == MachineType::Pointer()) {
     return Representation::External();
   }
 
   return Representation::Tagged();
 }
 
 }  // namespace internal
 }  // namespace v8