Port StringIteratorPrototypeNext to Torque

Bug: v8:8996
Change-Id: Ie4b17928fcb9d426bade5afc1238d24bc75ec13e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1594275
Commit-Queue: Z Nguyen-Huu <duongn@microsoft.com>
Reviewed-by: Simon Zünd <szuend@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Peter Wong <peter.wm.wong@gmail.com>
Cr-Commit-Position: refs/heads/master@{#61252}

src/builtins/base.tq

@@ -532,11 +532,6 @@ extern class JSGlobalObject extends JSObject {
   global_proxy: JSGlobalProxy;
 }
 
-extern class JSIteratorResult extends JSObject {
-  value: Object;
-  done: Boolean;
-}
-
 extern class JSAsyncFromSyncIterator extends JSObject {
   sync_iterator: JSReceiver;
   next: Object;
@@ -619,6 +614,10 @@ type ToIntegerTruncationMode
 constexpr 'CodeStubAssembler::ToIntegerTruncationMode';
 type AllocationFlags constexpr 'AllocationFlags';
 
+type UnicodeEncoding constexpr 'UnicodeEncoding';
+const UTF16:
+    constexpr UnicodeEncoding generates 'UnicodeEncoding::UTF16';
+
 extern class Foreign extends HeapObject { foreign_address: RawPtr; }
 
 extern class InterceptorInfo extends Struct {
@@ -991,6 +990,22 @@ extern class JSRegExp extends JSObject {
   flags: Smi | Undefined;
 }
 
+extern class JSIteratorResult extends JSObject {
+  value: Object;
+  done: Boolean;
+}
+
+macro NewJSIteratorResult(implicit context: Context)(
+    value: Object, done: Boolean): JSIteratorResult {
+  return new JSIteratorResult{
+    map: GetIteratorResultMap(),
+    properties_or_hash: kEmptyFixedArray,
+    elements: kEmptyFixedArray,
+    value,
+    done
+  };
+}
+
 // Note: Although a condition for a FastJSRegExp is having a positive smi
 // lastIndex (see RegExpBuiltinsAssembler::BranchIfFastRegExp), it is possible
 // for this to change without transitioning the transient type. As a precaution,
@@ -1185,6 +1200,8 @@ extern macro ThrowTypeError(implicit context: Context)(
     constexpr MessageTemplate, constexpr string): never;
 extern macro ThrowTypeError(implicit context: Context)(
     constexpr MessageTemplate, Object): never;
+extern macro ThrowTypeError(implicit context: Context)(
+    constexpr MessageTemplate, Object, Object): never;
 extern macro ThrowTypeError(implicit context: Context)(
     constexpr MessageTemplate, Object, Object, Object): never;
 extern macro ArraySpeciesCreate(Context, Object, Number): JSReceiver;
@@ -1456,6 +1473,8 @@ extern macro HeapObjectToJSDataView(HeapObject): JSDataView
     labels CastError;
 extern macro HeapObjectToJSProxy(HeapObject): JSProxy
     labels CastError;
+extern macro HeapObjectToJSStringIterator(HeapObject): JSStringIterator
+    labels CastError;
 extern macro HeapObjectToJSArrayBuffer(HeapObject): JSArrayBuffer
     labels CastError;
 extern macro TaggedToHeapObject(Object): HeapObject
@@ -1548,6 +1567,11 @@ Cast<JSProxy>(o: HeapObject): JSProxy
   return HeapObjectToJSProxy(o) otherwise CastError;
 }
 
+Cast<JSStringIterator>(o: HeapObject): JSStringIterator
+    labels CastError {
+  return HeapObjectToJSStringIterator(o) otherwise CastError;
+}
+
 Cast<JSTypedArray>(o: HeapObject): JSTypedArray
     labels CastError {
   if (IsJSTypedArray(o)) return %RawDownCast<JSTypedArray>(o);
@@ -2189,6 +2213,9 @@ macro GetProxyRevocableResultMap(implicit context: Context)(): Map {
   return UnsafeCast<Map>(
       LoadNativeContext(context)[PROXY_REVOCABLE_RESULT_MAP_INDEX]);
 }
+macro GetIteratorResultMap(implicit context: Context)(): Map {
+  return UnsafeCast<Map>(LoadNativeContext(context)[ITERATOR_RESULT_MAP_INDEX]);
+}
 macro GetInitialStringIteratorMap(implicit context: Context)(): Map {
   return UnsafeCast<Map>(
       LoadNativeContext(context)[INITIAL_STRING_ITERATOR_MAP_INDEX]);

src/builtins/builtins-definitions.h

@@ -999,9 +999,6 @@ namespace internal {
   /* ES6 #sec-string.raw */                                                    \
   CPP(StringRaw)                                                               \
                                                                                \
-  /* StringIterator */                                                         \
-  /* ES6 #sec-%stringiteratorprototype%.next */                                \
-  TFJ(StringIteratorPrototypeNext, 0, kReceiver)                               \
   TFS(StringToList, kSource)                                                   \
                                                                                \
   /* Symbol */                                                                 \

src/builtins/builtins-string-gen.cc

@@ -2268,59 +2268,6 @@ TNode<Int32T> StringBuiltinsAssembler::LoadSurrogatePairAt(
   return var_result.value();
 }
 
-// ES6 #sec-%stringiteratorprototype%.next
-TF_BUILTIN(StringIteratorPrototypeNext, StringBuiltinsAssembler) {
-  VARIABLE(var_value, MachineRepresentation::kTagged);
-  VARIABLE(var_done, MachineRepresentation::kTagged);
-
-  var_value.Bind(UndefinedConstant());
-  var_done.Bind(TrueConstant());
-
-  Label throw_bad_receiver(this), next_codepoint(this), return_result(this);
-
-  Node* context = Parameter(Descriptor::kContext);
-  Node* iterator = Parameter(Descriptor::kReceiver);
-
-  GotoIf(TaggedIsSmi(iterator), &throw_bad_receiver);
-  GotoIfNot(
-      InstanceTypeEqual(LoadInstanceType(iterator), JS_STRING_ITERATOR_TYPE),
-      &throw_bad_receiver);
-
-  Node* string = LoadObjectField(iterator, JSStringIterator::kStringOffset);
-  TNode<IntPtrT> position = SmiUntag(
-      CAST(LoadObjectField(iterator, JSStringIterator::kNextIndexOffset)));
-  TNode<IntPtrT> length = LoadStringLengthAsWord(string);
-
-  Branch(IntPtrLessThan(position, length), &next_codepoint, &return_result);
-
-  BIND(&next_codepoint);
-  {
-    UnicodeEncoding encoding = UnicodeEncoding::UTF16;
-    TNode<Int32T> ch = LoadSurrogatePairAt(string, length, position, encoding);
-    TNode<String> value = StringFromSingleCodePoint(ch, encoding);
-    var_value.Bind(value);
-    TNode<IntPtrT> length = LoadStringLengthAsWord(value);
-    StoreObjectFieldNoWriteBarrier(iterator, JSStringIterator::kNextIndexOffset,
-                                   SmiTag(Signed(IntPtrAdd(position, length))));
-    var_done.Bind(FalseConstant());
-    Goto(&return_result);
-  }
-
-  BIND(&return_result);
-  {
-    Node* result =
-        AllocateJSIteratorResult(context, var_value.value(), var_done.value());
-    Return(result);
-  }
-
-  BIND(&throw_bad_receiver);
-  {
-    // The {receiver} is not a valid JSGeneratorObject.
-    ThrowTypeError(context, MessageTemplate::kIncompatibleMethodReceiver,
-                   StringConstant("String Iterator.prototype.next"), iterator);
-  }
-}
-
 void StringBuiltinsAssembler::BranchIfStringPrimitiveWithNoCustomIteration(
     TNode<Object> object, TNode<Context> context, Label* if_true,
     Label* if_false) {

src/builtins/builtins-string-gen.h

@@ -28,6 +28,11 @@ class StringBuiltinsAssembler : public CodeStubAssembler {
                                                     Label* if_true,
                                                     Label* if_false);
 
+  TNode<Int32T> LoadSurrogatePairAt(SloppyTNode<String> string,
+                                    SloppyTNode<IntPtrT> length,
+                                    SloppyTNode<IntPtrT> index,
+                                    UnicodeEncoding encoding);
+
  protected:
   TNode<JSArray> StringToList(TNode<Context> context, TNode<String> string);
 
@@ -72,11 +77,6 @@ class StringBuiltinsAssembler : public CodeStubAssembler {
                         TNode<Object> default_return,
                         const StringAtAccessor& accessor);
 
-  TNode<Int32T> LoadSurrogatePairAt(SloppyTNode<String> string,
-                                    SloppyTNode<IntPtrT> length,
-                                    SloppyTNode<IntPtrT> index,
-                                    UnicodeEncoding encoding);
-
   void StringIndexOf(Node* const subject_string, Node* const search_string,
                      Node* const position,
                      const std::function<void(Node*)>& f_return);

src/builtins/object-fromentries.tq

@@ -42,9 +42,7 @@ namespace object {
     }
     label IfSlow {
       const result: JSObject = NewJSObject();
-      const fastIteratorResultMap: Map =
-          Cast<Map>(LoadNativeContext(context)[ITERATOR_RESULT_MAP_INDEX])
-          otherwise unreachable;
+      const fastIteratorResultMap: Map = GetIteratorResultMap();
       let i: iterator::IteratorRecord = iterator::GetIterator(iterable);
       try {
         assert(!IsNullOrUndefined(i.object));

src/builtins/string-iterator.tq

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include 'src/builtins/builtins-string-gen.h'
+
 namespace string_iterator {
 
   macro NewJSStringIterator(implicit context: Context)(
@@ -23,4 +25,29 @@ namespace string_iterator {
     const index: Smi = 0;
     return NewJSStringIterator(name, index);
   }
+
+  extern macro StringBuiltinsAssembler::LoadSurrogatePairAt(
+      String, intptr, intptr, constexpr UnicodeEncoding): int32;
+  extern macro StringFromSingleCodePoint(int32, constexpr UnicodeEncoding):
+      String;
+
+  // ES6 #sec-%stringiteratorprototype%.next
+  transitioning javascript builtin StringIteratorPrototypeNext(
+      implicit context: Context)(receiver: Object): JSIteratorResult {
+    const iterator = Cast<JSStringIterator>(receiver) otherwise ThrowTypeError(
+        kIncompatibleMethodReceiver, 'String Iterator.prototype.next',
+        receiver);
+    const string = iterator.string;
+    const position: intptr = SmiUntag(iterator.next_index);
+    const length: intptr = string.length_intptr;
+    if (position >= length) {
+      return NewJSIteratorResult(Undefined, True);
+    }
+    // Move to next codepoint.
+    const encoding = UTF16;
+    const ch = LoadSurrogatePairAt(string, length, position, encoding);
+    const value: String = StringFromSingleCodePoint(ch, encoding);
+    iterator.next_index = SmiTag(position + value.length_intptr);
+    return NewJSIteratorResult(value, False);
+  }
 }

src/code-stub-assembler.cc

@@ -6208,6 +6208,11 @@ TNode<BoolT> CodeStubAssembler::IsJSProxy(SloppyTNode<HeapObject> object) {
   return HasInstanceType(object, JS_PROXY_TYPE);
 }
 
+TNode<BoolT> CodeStubAssembler::IsJSStringIterator(
+    SloppyTNode<HeapObject> object) {
+  return HasInstanceType(object, JS_STRING_ITERATOR_TYPE);
+}
+
 TNode<BoolT> CodeStubAssembler::IsJSGlobalProxy(
     SloppyTNode<HeapObject> object) {
   return HasInstanceType(object, JS_GLOBAL_PROXY_TYPE);

src/code-stub-assembler.h

@@ -365,6 +365,12 @@ class V8_EXPORT_PRIVATE CodeStubAssembler
     return CAST(heap_object);
   }
 
+  TNode<JSStringIterator> HeapObjectToJSStringIterator(
+      TNode<HeapObject> heap_object, Label* fail) {
+    GotoIfNot(IsJSStringIterator(heap_object), fail);
+    return CAST(heap_object);
+  }
+
   TNode<JSReceiver> HeapObjectToCallable(TNode<HeapObject> heap_object,
                                          Label* fail) {
     GotoIfNot(IsCallable(heap_object), fail);
@@ -2193,6 +2199,7 @@ class V8_EXPORT_PRIVATE CodeStubAssembler
   TNode<BoolT> IsJSPromiseMap(SloppyTNode<Map> map);
   TNode<BoolT> IsJSPromise(SloppyTNode<HeapObject> object);
   TNode<BoolT> IsJSProxy(SloppyTNode<HeapObject> object);
+  TNode<BoolT> IsJSStringIterator(SloppyTNode<HeapObject> object);
   TNode<BoolT> IsJSReceiverInstanceType(SloppyTNode<Int32T> instance_type);
   TNode<BoolT> IsJSReceiverMap(SloppyTNode<Map> map);
   TNode<BoolT> IsJSReceiver(SloppyTNode<HeapObject> object);