[cleanup] Refactor IterableToFixedArrayForWasm

It doesn't need to implement its own iteration logic, if we refactor a bit.

BUG=v8:10425

Change-Id: I9b33911c2fab9ac85cae847473dbef0c2e88ea96
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2153224Reviewed-by: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Sathya Gunasekaran  <gsathya@chromium.org>
Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67232}

src/builtins/builtins-iterator-gen.cc

@@ -178,14 +178,24 @@ void IteratorBuiltinsAssembler::IteratorCloseOnException(
 
 TNode<JSArray> IteratorBuiltinsAssembler::IterableToList(
     TNode<Context> context, TNode<Object> iterable, TNode<Object> iterator_fn) {
+  GrowableFixedArray values(state());
+  FillFixedArrayFromIterable(context, iterable, iterator_fn, &values);
+  return values.ToJSArray(context);
+}
+
+void IteratorBuiltinsAssembler::FillFixedArrayFromIterable(
+    TNode<Context> context, TNode<Object> iterable, TNode<Object> iterator_fn,
+    GrowableFixedArray* values) {
   // 1. Let iteratorRecord be ? GetIterator(items, method).
   IteratorRecord iterator_record = GetIterator(context, iterable, iterator_fn);
 
   // 2. Let values be a new empty List.
-  GrowableFixedArray values(state());
 
-  Label loop_start(
-      this, {values.var_array(), values.var_length(), values.var_capacity()}),
+  // The GrowableFixedArray has already been created. It's ok if we do this step
+  // out of order, since creating an empty List is not observable.
+
+  Label loop_start(this, {values->var_array(), values->var_length(),
+                          values->var_capacity()}),
       done(this);
   Goto(&loop_start);
   // 3. Let next be true.
@@ -198,12 +208,11 @@ TNode<JSArray> IteratorBuiltinsAssembler::IterableToList(
     //   i. Let nextValue be ? IteratorValue(next).
     TNode<Object> next_value = IteratorValue(context, next);
     //   ii. Append nextValue to the end of the List values.
-    values.Push(next_value);
+    values->Push(next_value);
     Goto(&loop_start);
   }
 
   BIND(&done);
-  return values.ToJSArray(context);
 }
 
 TF_BUILTIN(IterableToList, IteratorBuiltinsAssembler) {
@@ -220,25 +229,12 @@ TF_BUILTIN(IterableToFixedArrayForWasm, IteratorBuiltinsAssembler) {
   TNode<Smi> expected_length = CAST(Parameter(Descriptor::kExpectedLength));
 
   TNode<Object> iterator_fn = GetIteratorMethod(context, iterable);
-
-  IteratorRecord iterator_record = GetIterator(context, iterable, iterator_fn);
-
   GrowableFixedArray values(state());
 
-  Label loop_start(
-      this, {values.var_array(), values.var_length(), values.var_capacity()}),
-      compare_length(this), done(this);
-  Goto(&loop_start);
-  BIND(&loop_start);
-  {
-    TNode<JSReceiver> next =
-        IteratorStep(context, iterator_record, &compare_length);
-    TNode<Object> next_value = IteratorValue(context, next);
-    values.Push(next_value);
-    Goto(&loop_start);
-  }
+  Label done(this);
+
+  FillFixedArrayFromIterable(context, iterable, iterator_fn, &values);
 
-  BIND(&compare_length);
   GotoIf(WordEqual(SmiUntag(expected_length), values.var_length()->value()),
          &done);
   Return(CallRuntime(

src/builtins/builtins-iterator-gen.h

@@ -12,6 +12,8 @@ namespace internal {
 
 using compiler::Node;
 
+class GrowableFixedArray;
+
 class IteratorBuiltinsAssembler : public CodeStubAssembler {
  public:
   explicit IteratorBuiltinsAssembler(compiler::CodeAssemblerState* state)
@@ -65,6 +67,11 @@ class IteratorBuiltinsAssembler : public CodeStubAssembler {
   TNode<JSArray> IterableToList(TNode<Context> context, TNode<Object> iterable,
                                 TNode<Object> iterator_fn);
 
+  void FillFixedArrayFromIterable(TNode<Context> context,
+                                  TNode<Object> iterable,
+                                  TNode<Object> iterator_fn,
+                                  GrowableFixedArray* values);
+
   // Currently at https://tc39.github.io/proposal-intl-list-format/
   // #sec-createstringlistfromiterable
   TNode<JSArray> StringListFromIterable(TNode<Context> context,