Revert of [turbofan] inline %StringIteratorPrototype%.next in...

Revert of [turbofan] inline %StringIteratorPrototype%.next in JSBuiltinReducer. (patchset #12 id:210001 of https://codereview.chromium.org/2373983004/ )

Reason for revert:
[Sheriff] Speculative revert for win dbg: https://build.chromium.org/p/client.v8/builders/V8%20Win32%20-%20debug/builds/5029

Or we have an infra problem. Manual build before seems fine:
https://build.chromium.org/p/client.v8/builders/V8%20Win32%20-%20debug/builds/5030

Original issue's description:
> [turbofan] inline %StringIteratorPrototype%.next in JSBuiltinReducer.
>
> Implement the logic for StringIterator.prototype.next in the JSBuiltinReducer in order to allow inlining when the receiver is a JS_STRING_ITERATOR_TYPE map, built ontop of the SimplifiedOperators StringCharCodeAt and the newly added StringFromCodePoint.
>
> Also introduces a new StringFromCodePoint simplified op which may be useful for other String builtins, such as String.fromCodePoint()
>
> BUG=v8:5388
> R=bmeurer@chromium.org, mstarzinger@chromium.org
>
> Committed: https://crrev.com/aed32e0f22353527993de8bceaf246fc744558f5
> Cr-Commit-Position: refs/heads/master@{#39994}

TBR=bmeurer@chromium.org,mvstanton@chromium.org,caitp@igalia.com
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:5388

Review-Url: https://codereview.chromium.org/2397753003
Cr-Commit-Position: refs/heads/master@{#39995}

src/bootstrapper.cc

@@ -1450,7 +1450,6 @@ void Genesis::InitializeGlobal(Handle<JSGlobalObject> global_object,
         InstallFunction(string_iterator_prototype, "next", JS_OBJECT_TYPE,
                         JSObject::kHeaderSize, MaybeHandle<JSObject>(),
                         Builtins::kStringIteratorPrototypeNext);
-    next->shared()->set_builtin_function_id(kStringIteratorNext);
 
     // Set the expected parameters for %StringIteratorPrototype%.next to 0 (not
     // including the receiver), as required by the builtin.

src/code-stub-assembler.h

@@ -19,6 +19,12 @@ class StubCache;
 
 enum class PrimitiveType { kBoolean, kNumber, kString, kSymbol };
 
+enum class UnicodeEncoding {
+  // Different unicode encodings in a |word32|:
+  UTF16,  // hi 16bits -> trailing surrogate or 0, low 16bits -> lead surrogate
+  UTF32,  // full UTF32 code unit / Unicode codepoint
+};
+
 #define HEAP_CONSTANT_LIST(V)                 \
   V(BooleanMap, BooleanMap)                   \
   V(empty_string, EmptyString)                \

src/compiler/access-builder.cc

@@ -548,24 +548,6 @@ FieldAccess AccessBuilder::ForJSGlobalObjectNativeContext() {
   return access;
 }
 
-// static
-FieldAccess AccessBuilder::ForJSStringIteratorString() {
-  FieldAccess access = {
-      kTaggedBase,    JSStringIterator::kStringOffset, Handle<Name>(),
-      Type::String(), MachineType::TaggedPointer(),    kPointerWriteBarrier};
-  return access;
-}
-
-// static
-FieldAccess AccessBuilder::ForJSStringIteratorIndex() {
-  FieldAccess access = {kTaggedBase,
-                        JSStringIterator::kNextIndexOffset,
-                        Handle<Name>(),
-                        TypeCache::Get().kStringLengthType,
-                        MachineType::TaggedSigned(),
-                        kNoWriteBarrier};
-  return access;
-}
 
 // static
 FieldAccess AccessBuilder::ForValue() {

src/compiler/access-builder.h

@@ -182,12 +182,6 @@ class AccessBuilder final : public AllStatic {
   // Provides access to JSGlobalObject::native_context() field.
   static FieldAccess ForJSGlobalObjectNativeContext();
 
-  // Provides access to JSStringIterator::string() field.
-  static FieldAccess ForJSStringIteratorString();
-
-  // Provides access to JSStringIterator::index() field.
-  static FieldAccess ForJSStringIteratorIndex();
-
   // Provides access to JSValue::value() field.
   static FieldAccess ForValue();
 

src/compiler/effect-control-linearizer.cc

@@ -719,9 +719,6 @@ bool EffectControlLinearizer::TryWireInStateEffect(Node* node,
     case IrOpcode::kStringFromCharCode:
       state = LowerStringFromCharCode(node, *effect, *control);
       break;
-    case IrOpcode::kStringFromCodePoint:
-      state = LowerStringFromCodePoint(node, *effect, *control);
-      break;
     case IrOpcode::kStringCharCodeAt:
       state = LowerStringCharCodeAt(node, *effect, *control);
       break;
@@ -2549,199 +2546,6 @@ EffectControlLinearizer::LowerStringFromCharCode(Node* node, Node* effect,
   return ValueEffectControl(value, effect, control);
 }
 
-EffectControlLinearizer::ValueEffectControl
-EffectControlLinearizer::LowerStringFromCodePoint(Node* node, Node* effect,
-                                                  Node* control) {
-  Node* value = node->InputAt(0);
-  Node* code = value;
-
-  Node* etrue0 = effect;
-  Node* vtrue0;
-
-  // Check if the {code} is a single code unit
-  Node* check0 = graph()->NewNode(machine()->Uint32LessThanOrEqual(), code,
-                                  jsgraph()->Uint32Constant(0xFFFF));
-  Node* branch0 =
-      graph()->NewNode(common()->Branch(BranchHint::kTrue), check0, control);
-
-  Node* if_true0 = graph()->NewNode(common()->IfTrue(), branch0);
-  {
-    // Check if the {code} is a one byte character
-    Node* check1 = graph()->NewNode(
-        machine()->Uint32LessThanOrEqual(), code,
-        jsgraph()->Uint32Constant(String::kMaxOneByteCharCode));
-    Node* branch1 =
-        graph()->NewNode(common()->Branch(BranchHint::kTrue), check1, if_true0);
-
-    Node* if_true1 = graph()->NewNode(common()->IfTrue(), branch1);
-    Node* etrue1 = etrue0;
-    Node* vtrue1;
-    {
-      // Load the isolate wide single character string cache.
-      Node* cache =
-          jsgraph()->HeapConstant(factory()->single_character_string_cache());
-
-      // Compute the {cache} index for {code}.
-      Node* index =
-          machine()->Is32()
-              ? code
-              : graph()->NewNode(machine()->ChangeUint32ToUint64(), code);
-
-      // Check if we have an entry for the {code} in the single character string
-      // cache already.
-      Node* entry = etrue1 = graph()->NewNode(
-          simplified()->LoadElement(AccessBuilder::ForFixedArrayElement()),
-          cache, index, etrue1, if_true1);
-
-      Node* check2 = graph()->NewNode(machine()->WordEqual(), entry,
-                                      jsgraph()->UndefinedConstant());
-      Node* branch2 = graph()->NewNode(common()->Branch(BranchHint::kFalse),
-                                       check2, if_true1);
-
-      Node* if_true2 = graph()->NewNode(common()->IfTrue(), branch2);
-      Node* etrue2 = etrue1;
-      Node* vtrue2;
-      {
-        // Allocate a new SeqOneByteString for {code}.
-        vtrue2 = etrue2 = graph()->NewNode(
-            simplified()->Allocate(NOT_TENURED),
-            jsgraph()->Int32Constant(SeqOneByteString::SizeFor(1)), etrue2,
-            if_true2);
-        etrue2 = graph()->NewNode(
-            simplified()->StoreField(AccessBuilder::ForMap()), vtrue2,
-            jsgraph()->HeapConstant(factory()->one_byte_string_map()), etrue2,
-            if_true2);
-        etrue2 = graph()->NewNode(
-            simplified()->StoreField(AccessBuilder::ForNameHashField()), vtrue2,
-            jsgraph()->IntPtrConstant(Name::kEmptyHashField), etrue2, if_true2);
-        etrue2 = graph()->NewNode(
-            simplified()->StoreField(AccessBuilder::ForStringLength()), vtrue2,
-            jsgraph()->SmiConstant(1), etrue2, if_true2);
-        etrue2 = graph()->NewNode(
-            machine()->Store(StoreRepresentation(MachineRepresentation::kWord8,
-                                                 kNoWriteBarrier)),
-            vtrue2, jsgraph()->IntPtrConstant(SeqOneByteString::kHeaderSize -
-                                              kHeapObjectTag),
-            code, etrue2, if_true2);
-
-        // Remember it in the {cache}.
-        etrue2 = graph()->NewNode(
-            simplified()->StoreElement(AccessBuilder::ForFixedArrayElement()),
-            cache, index, vtrue2, etrue2, if_true2);
-      }
-
-      // Use the {entry} from the {cache}.
-      Node* if_false2 = graph()->NewNode(common()->IfFalse(), branch2);
-      Node* efalse2 = etrue0;
-      Node* vfalse2 = entry;
-
-      if_true1 = graph()->NewNode(common()->Merge(2), if_true2, if_false2);
-      etrue1 =
-          graph()->NewNode(common()->EffectPhi(2), etrue2, efalse2, if_true1);
-      vtrue1 =
-          graph()->NewNode(common()->Phi(MachineRepresentation::kTagged, 2),
-                           vtrue2, vfalse2, if_true1);
-    }
-
-    Node* if_false1 = graph()->NewNode(common()->IfFalse(), branch1);
-    Node* efalse1 = effect;
-    Node* vfalse1;
-    {
-      // Allocate a new SeqTwoByteString for {code}.
-      vfalse1 = efalse1 = graph()->NewNode(
-          simplified()->Allocate(NOT_TENURED),
-          jsgraph()->Int32Constant(SeqTwoByteString::SizeFor(1)), efalse1,
-          if_false1);
-      efalse1 = graph()->NewNode(
-          simplified()->StoreField(AccessBuilder::ForMap()), vfalse1,
-          jsgraph()->HeapConstant(factory()->string_map()), efalse1, if_false1);
-      efalse1 = graph()->NewNode(
-          simplified()->StoreField(AccessBuilder::ForNameHashField()), vfalse1,
-          jsgraph()->IntPtrConstant(Name::kEmptyHashField), efalse1, if_false1);
-      efalse1 = graph()->NewNode(
-          simplified()->StoreField(AccessBuilder::ForStringLength()), vfalse1,
-          jsgraph()->SmiConstant(1), efalse1, if_false1);
-      efalse1 = graph()->NewNode(
-          machine()->Store(StoreRepresentation(MachineRepresentation::kWord16,
-                                               kNoWriteBarrier)),
-          vfalse1, jsgraph()->IntPtrConstant(SeqTwoByteString::kHeaderSize -
-                                             kHeapObjectTag),
-          code, efalse1, if_false1);
-    }
-
-    if_true0 = graph()->NewNode(common()->Merge(2), if_true1, if_false1);
-    etrue0 =
-        graph()->NewNode(common()->EffectPhi(2), etrue1, efalse1, if_true0);
-    vtrue0 = graph()->NewNode(common()->Phi(MachineRepresentation::kTagged, 2),
-                              vtrue1, vfalse1, if_true0);
-  }
-
-  // Generate surrogate pair string
-  Node* if_false0 = graph()->NewNode(common()->IfFalse(), branch0);
-  Node* efalse0 = effect;
-  Node* vfalse0;
-  {
-    switch (UnicodeEncodingOf(node->op())) {
-      case UnicodeEncoding::UTF16:
-        break;
-
-      case UnicodeEncoding::UTF32: {
-        // Convert UTF32 to UTF16 code units, and store as a 32 bit word.
-        Node* lead_offset = jsgraph()->Int32Constant(0xD800 - (0x10000 >> 10));
-
-        // lead = (codepoint >> 10) + LEAD_OFFSET
-        Node* lead =
-            graph()->NewNode(machine()->Int32Add(),
-                             graph()->NewNode(machine()->Word32Shr(), code,
-                                              jsgraph()->Int32Constant(10)),
-                             lead_offset);
-
-        // trail = (codepoint & 0x3FF) + 0xDC00;
-        Node* trail =
-            graph()->NewNode(machine()->Int32Add(),
-                             graph()->NewNode(machine()->Word32And(), code,
-                                              jsgraph()->Int32Constant(0x3FF)),
-                             jsgraph()->Int32Constant(0xDC00));
-
-        // codpoint = (trail << 16) | lead;
-        code = graph()->NewNode(machine()->Word32Or(),
-                                graph()->NewNode(machine()->Word32Shl(), trail,
-                                                 jsgraph()->Int32Constant(16)),
-                                lead);
-        break;
-      }
-    }
-
-    // Allocate a new SeqTwoByteString for {code}.
-    vfalse0 = efalse0 =
-        graph()->NewNode(simplified()->Allocate(NOT_TENURED),
-                         jsgraph()->Int32Constant(SeqTwoByteString::SizeFor(2)),
-                         efalse0, if_false0);
-    efalse0 = graph()->NewNode(
-        simplified()->StoreField(AccessBuilder::ForMap()), vfalse0,
-        jsgraph()->HeapConstant(factory()->string_map()), efalse0, if_false0);
-    efalse0 = graph()->NewNode(
-        simplified()->StoreField(AccessBuilder::ForNameHashField()), vfalse0,
-        jsgraph()->IntPtrConstant(Name::kEmptyHashField), efalse0, if_false0);
-    efalse0 = graph()->NewNode(
-        simplified()->StoreField(AccessBuilder::ForStringLength()), vfalse0,
-        jsgraph()->SmiConstant(2), efalse0, if_false0);
-    efalse0 = graph()->NewNode(
-        machine()->Store(StoreRepresentation(MachineRepresentation::kWord32,
-                                             kNoWriteBarrier)),
-        vfalse0, jsgraph()->IntPtrConstant(SeqTwoByteString::kHeaderSize -
-                                           kHeapObjectTag),
-        code, efalse0, if_false0);
-  }
-
-  control = graph()->NewNode(common()->Merge(2), if_true0, if_false0);
-  effect = graph()->NewNode(common()->EffectPhi(2), etrue0, efalse0, control);
-  value = graph()->NewNode(common()->Phi(MachineRepresentation::kTagged, 2),
-                           vtrue0, vfalse0, control);
-
-  return ValueEffectControl(value, effect, control);
-}
-
 EffectControlLinearizer::ValueEffectControl
 EffectControlLinearizer::LowerStringComparison(Callable const& callable,
                                                Node* node, Node* effect,

src/compiler/effect-control-linearizer.h

@@ -142,8 +142,6 @@ class EffectControlLinearizer {
                                            Node* control);
   ValueEffectControl LowerStringFromCharCode(Node* node, Node* effect,
                                              Node* control);
-  ValueEffectControl LowerStringFromCodePoint(Node* node, Node* effect,
-                                              Node* control);
   ValueEffectControl LowerStringEqual(Node* node, Node* effect, Node* control);
   ValueEffectControl LowerStringLessThan(Node* node, Node* effect,
                                          Node* control);

src/compiler/js-builtin-reducer.cc

@@ -1026,139 +1026,6 @@ Reduction JSBuiltinReducer::ReduceStringCharCodeAt(Node* node) {
   return NoChange();
 }
 
-Reduction JSBuiltinReducer::ReduceStringIteratorNext(Node* node) {
-  Node* receiver = NodeProperties::GetValueInput(node, 1);
-  Node* effect = NodeProperties::GetEffectInput(node);
-  Node* control = NodeProperties::GetControlInput(node);
-  Node* context = NodeProperties::GetContextInput(node);
-  if (HasInstanceTypeWitness(receiver, effect, JS_STRING_ITERATOR_TYPE)) {
-    Node* string = effect = graph()->NewNode(
-        simplified()->LoadField(AccessBuilder::ForJSStringIteratorString()),
-        receiver, effect, control);
-    Node* index = effect = graph()->NewNode(
-        simplified()->LoadField(AccessBuilder::ForJSStringIteratorIndex()),
-        receiver, effect, control);
-    Node* length = effect = graph()->NewNode(
-        simplified()->LoadField(AccessBuilder::ForStringLength()), string,
-        effect, control);
-
-    // branch0: if (index < length)
-    Node* check0 =
-        graph()->NewNode(simplified()->NumberLessThan(), index, length);
-    Node* branch0 =
-        graph()->NewNode(common()->Branch(BranchHint::kTrue), check0, control);
-
-    Node* etrue0 = effect;
-    Node* if_true0 = graph()->NewNode(common()->IfTrue(), branch0);
-    Node* done_true;
-    Node* vtrue0;
-    {
-      done_true = jsgraph()->FalseConstant();
-      Node* lead = graph()->NewNode(simplified()->StringCharCodeAt(), string,
-                                    index, if_true0);
-
-      // branch1: if ((lead & 0xFC00) === 0xD800)
-      Node* check1 = graph()->NewNode(
-          simplified()->NumberEqual(),
-          graph()->NewNode(simplified()->NumberBitwiseAnd(), lead,
-                           jsgraph()->Int32Constant(0xFC00)),
-          jsgraph()->Int32Constant(0xD800));
-      Node* branch1 = graph()->NewNode(common()->Branch(BranchHint::kFalse),
-                                       check1, if_true0);
-      Node* if_true1 = graph()->NewNode(common()->IfTrue(), branch1);
-      Node* vtrue1;
-      {
-        Node* next_index = graph()->NewNode(simplified()->NumberAdd(), index,
-                                            jsgraph()->OneConstant());
-        // branch2: if ((index + 1) < length)
-        Node* check2 = graph()->NewNode(simplified()->NumberLessThan(),
-                                        next_index, length);
-        Node* branch2 = graph()->NewNode(common()->Branch(BranchHint::kTrue),
-                                         check2, if_true1);
-        Node* if_true2 = graph()->NewNode(common()->IfTrue(), branch2);
-        Node* vtrue2;
-        {
-          Node* trail = graph()->NewNode(simplified()->StringCharCodeAt(),
-                                         string, next_index, if_true2);
-          // branch3: if ((trail & 0xFC00) === 0xDC00)
-          Node* check3 = graph()->NewNode(
-              simplified()->NumberEqual(),
-              graph()->NewNode(simplified()->NumberBitwiseAnd(), trail,
-                               jsgraph()->Int32Constant(0xFC00)),
-              jsgraph()->Int32Constant(0xDC00));
-          Node* branch3 = graph()->NewNode(common()->Branch(BranchHint::kTrue),
-                                           check3, if_true2);
-          Node* if_true3 = graph()->NewNode(common()->IfTrue(), branch3);
-          Node* vtrue3;
-          {
-            vtrue3 = graph()->NewNode(
-                simplified()->NumberBitwiseOr(),
-                graph()->NewNode(simplified()->NumberShiftLeft(), trail,
-                                 jsgraph()->Int32Constant(16)),
-                lead);
-          }
-
-          Node* if_false3 = graph()->NewNode(common()->IfFalse(), branch3);
-          Node* vfalse3 = lead;
-          if_true2 = graph()->NewNode(common()->Merge(2), if_true3, if_false3);
-          vtrue2 =
-              graph()->NewNode(common()->Phi(MachineRepresentation::kWord32, 2),
-                               vtrue3, vfalse3, if_true2);
-        }
-
-        Node* if_false2 = graph()->NewNode(common()->IfFalse(), branch2);
-        Node* vfalse2 = lead;
-        if_true1 = graph()->NewNode(common()->Merge(2), if_true2, if_false2);
-        vtrue1 =
-            graph()->NewNode(common()->Phi(MachineRepresentation::kWord32, 2),
-                             vtrue2, vfalse2, if_true1);
-      }
-
-      Node* if_false1 = graph()->NewNode(common()->IfFalse(), branch1);
-      Node* vfalse1 = lead;
-      if_true0 = graph()->NewNode(common()->Merge(2), if_true1, if_false1);
-      vtrue0 =
-          graph()->NewNode(common()->Phi(MachineRepresentation::kWord32, 2),
-                           vtrue1, vfalse1, if_true0);
-      vtrue0 = graph()->NewNode(
-          simplified()->StringFromCodePoint(UnicodeEncoding::UTF16), vtrue0);
-
-      // Update iterator.[[NextIndex]]
-      Node* char_length = etrue0 = graph()->NewNode(
-          simplified()->LoadField(AccessBuilder::ForStringLength()), vtrue0,
-          etrue0, if_true0);
-      index = graph()->NewNode(simplified()->NumberAdd(), index, char_length);
-      etrue0 = graph()->NewNode(
-          simplified()->StoreField(AccessBuilder::ForJSStringIteratorIndex()),
-          receiver, index, etrue0, if_true0);
-    }
-
-    Node* if_false0 = graph()->NewNode(common()->IfFalse(), branch0);
-    Node* done_false;
-    Node* vfalse0;
-    {
-      vfalse0 = jsgraph()->UndefinedConstant();
-      done_false = jsgraph()->TrueConstant();
-    }
-
-    control = graph()->NewNode(common()->Merge(2), if_true0, if_false0);
-    effect = graph()->NewNode(common()->EffectPhi(2), etrue0, effect, control);
-    Node* value =
-        graph()->NewNode(common()->Phi(MachineRepresentation::kTagged, 2),
-                         vtrue0, vfalse0, control);
-    Node* done =
-        graph()->NewNode(common()->Phi(MachineRepresentation::kTagged, 2),
-                         done_true, done_false, control);
-
-    value = effect = graph()->NewNode(javascript()->CreateIterResultObject(),
-                                      value, done, context, effect);
-
-    ReplaceWithValue(node, value, effect, control);
-    return Replace(value);
-  }
-  return NoChange();
-}
-
 Reduction JSBuiltinReducer::ReduceArrayBufferViewAccessor(
     Node* node, InstanceType instance_type, FieldAccess const& access) {
   Node* receiver = NodeProperties::GetValueInput(node, 1);
@@ -1328,8 +1195,6 @@ Reduction JSBuiltinReducer::Reduce(Node* node) {
       return ReduceStringCharAt(node);
     case kStringCharCodeAt:
       return ReduceStringCharCodeAt(node);
-    case kStringIteratorNext:
-      return ReduceStringIteratorNext(node);
     case kDataViewByteLength:
       return ReduceArrayBufferViewAccessor(
           node, JS_DATA_VIEW_TYPE,
@@ -1389,10 +1254,6 @@ SimplifiedOperatorBuilder* JSBuiltinReducer::simplified() const {
   return jsgraph()->simplified();
 }
 
-JSOperatorBuilder* JSBuiltinReducer::javascript() const {
-  return jsgraph()->javascript();
-}
-
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8

src/compiler/js-builtin-reducer.h

@@ -21,7 +21,6 @@ namespace compiler {
 class CommonOperatorBuilder;
 struct FieldAccess;
 class JSGraph;
-class JSOperatorBuilder;
 class SimplifiedOperatorBuilder;
 class TypeCache;
 
@@ -87,7 +86,6 @@ class JSBuiltinReducer final : public AdvancedReducer {
   Reduction ReduceStringCharAt(Node* node);
   Reduction ReduceStringCharCodeAt(Node* node);
   Reduction ReduceStringFromCharCode(Node* node);
-  Reduction ReduceStringIteratorNext(Node* node);
   Reduction ReduceArrayBufferViewAccessor(Node* node,
                                           InstanceType instance_type,
                                           FieldAccess const& access);
@@ -102,7 +100,6 @@ class JSBuiltinReducer final : public AdvancedReducer {
   Isolate* isolate() const;
   CommonOperatorBuilder* common() const;
   SimplifiedOperatorBuilder* simplified() const;
-  JSOperatorBuilder* javascript() const;
   CompilationDependencies* dependencies() const { return dependencies_; }
 
   CompilationDependencies* const dependencies_;

src/compiler/opcodes.h

@@ -284,7 +284,6 @@
   V(BooleanNot)                     \
   V(StringCharCodeAt)               \
   V(StringFromCharCode)             \
-  V(StringFromCodePoint)            \
   V(CheckBounds)                    \
   V(CheckIf)                        \
   V(CheckMaps)                      \

src/compiler/simplified-lowering.cc

@@ -2056,11 +2056,6 @@ class RepresentationSelector {
                   MachineRepresentation::kTagged);
         return;
       }
-      case IrOpcode::kStringFromCodePoint: {
-        VisitUnop(node, UseInfo::TruncatingWord32(),
-                  MachineRepresentation::kTagged);
-        return;
-      }
 
       case IrOpcode::kCheckBounds: {
         Type* index_type = TypeOf(node->InputAt(0));

src/compiler/simplified-operator.cc

@@ -336,11 +336,6 @@ PretenureFlag PretenureFlagOf(const Operator* op) {
   return OpParameter<PretenureFlag>(op);
 }
 
-UnicodeEncoding UnicodeEncodingOf(const Operator* op) {
-  DCHECK(op->opcode() == IrOpcode::kStringFromCodePoint);
-  return OpParameter<UnicodeEncoding>(op);
-}
-
 #define PURE_OP_LIST(V)                                          \
   V(BooleanNot, Operator::kNoProperties, 1, 0)                   \
   V(NumberEqual, Operator::kCommutative, 2, 0)                   \
@@ -473,17 +468,6 @@ struct SimplifiedOperatorGlobalCache final {
   CHECKED_OP_LIST(CHECKED)
 #undef CHECKED
 
-  template <UnicodeEncoding kEncoding>
-  struct StringFromCodePointOperator final : public Operator {
-    StringFromCodePointOperator()
-        : Operator(IrOpcode::kStringFromCodePoint, Operator::kPure,
-                   "StringFromCodePoint", 1, 0, 0, 1, 0, 0) {}
-  };
-  StringFromCodePointOperator<UnicodeEncoding::UTF16>
-      kStringFromCodePointOperatorUTF16;
-  StringFromCodePointOperator<UnicodeEncoding::UTF32>
-      kStringFromCodePointOperatorUTF32;
-
   struct ArrayBufferWasNeuteredOperator final : public Operator {
     ArrayBufferWasNeuteredOperator()
         : Operator(IrOpcode::kArrayBufferWasNeutered, Operator::kEliminatable,
@@ -770,18 +754,6 @@ const Operator* SimplifiedOperatorBuilder::StoreBuffer(BufferAccess access) {
   return nullptr;
 }
 
-const Operator* SimplifiedOperatorBuilder::StringFromCodePoint(
-    UnicodeEncoding encoding) {
-  switch (encoding) {
-    case UnicodeEncoding::UTF16:
-      return &cache_.kStringFromCodePointOperatorUTF16;
-    case UnicodeEncoding::UTF32:
-      return &cache_.kStringFromCodePointOperatorUTF32;
-  }
-  UNREACHABLE();
-  return nullptr;
-}
-
 #define SPECULATIVE_NUMBER_BINOP(Name)                                        \
   const Operator* SimplifiedOperatorBuilder::Name(NumberOperationHint hint) { \
     switch (hint) {                                                           \

src/compiler/simplified-operator.h

@@ -185,8 +185,6 @@ NumberOperationHint NumberOperationHintOf(const Operator* op)
 
 PretenureFlag PretenureFlagOf(const Operator* op) WARN_UNUSED_RESULT;
 
-UnicodeEncoding UnicodeEncodingOf(const Operator*) WARN_UNUSED_RESULT;
-
 // Interface for building simplified operators, which represent the
 // medium-level operations of V8, including adding numbers, allocating objects,
 // indexing into objects and arrays, etc.
@@ -291,7 +289,6 @@ class SimplifiedOperatorBuilder final : public ZoneObject {
   const Operator* StringLessThanOrEqual();
   const Operator* StringCharCodeAt();
   const Operator* StringFromCharCode();
-  const Operator* StringFromCodePoint(UnicodeEncoding encoding);
 
   const Operator* PlainPrimitiveToNumber();
   const Operator* PlainPrimitiveToWord32();

src/compiler/typer.cc

@@ -295,7 +295,6 @@ class Typer::Visitor : public Reducer {
 
   static Type* ReferenceEqualTyper(Type*, Type*, Typer*);
   static Type* StringFromCharCodeTyper(Type*, Typer*);
-  static Type* StringFromCodePointTyper(Type*, Typer*);
 
   Reduction UpdateType(Node* node, Type* current) {
     if (NodeProperties::IsTyped(node)) {
@@ -1366,10 +1365,6 @@ Type* Typer::Visitor::JSCallFunctionTyper(Type* fun, Typer* t) {
         case kStringToLowerCase:
         case kStringToUpperCase:
           return Type::String();
-
-        case kStringIteratorNext:
-          return Type::OtherObject();
-
         // Array functions.
         case kArrayIndexOf:
         case kArrayLastIndexOf:
@@ -1556,19 +1551,6 @@ Type* Typer::Visitor::StringFromCharCodeTyper(Type* type, Typer* t) {
   return Type::String();
 }
 
-Type* Typer::Visitor::StringFromCodePointTyper(Type* type, Typer* t) {
-  type = NumberToUint32(ToNumber(type, t), t);
-  Factory* f = t->isolate()->factory();
-  double min = type->Min();
-  double max = type->Max();
-  if (min == max) {
-    uint32_t code = static_cast<uint32_t>(min) & String::kMaxUtf16CodeUnitU;
-    Handle<String> string = f->LookupSingleCharacterStringFromCode(code);
-    return Type::Constant(string, t->zone());
-  }
-  return Type::String();
-}
-
 Type* Typer::Visitor::TypeStringCharCodeAt(Node* node) {
   // TODO(bmeurer): We could do better here based on inputs.
   return Type::Range(0, kMaxUInt16, zone());
@@ -1578,10 +1560,6 @@ Type* Typer::Visitor::TypeStringFromCharCode(Node* node) {
   return TypeUnaryOp(node, StringFromCharCodeTyper);
 }
 
-Type* Typer::Visitor::TypeStringFromCodePoint(Node* node) {
-  return TypeUnaryOp(node, StringFromCodePointTyper);
-}
-
 Type* Typer::Visitor::TypeCheckBounds(Node* node) {
   Type* index = Operand(node, 0);
   Type* length = Operand(node, 1);

src/compiler/verifier.cc

@@ -846,11 +846,6 @@ void Verifier::Visitor::Check(Node* node) {
       CheckValueInputIs(node, 0, Type::Number());
       CheckTypeIs(node, Type::String());
       break;
-    case IrOpcode::kStringFromCodePoint:
-      // (Unsigned32) -> String
-      CheckValueInputIs(node, 0, Type::Number());
-      CheckTypeIs(node, Type::String());
-      break;
     case IrOpcode::kReferenceEqual: {
       // (Unique, Any) -> Boolean  and
       // (Any, Unique) -> Boolean

src/globals.h

@@ -1234,27 +1234,6 @@ enum LiveEditFrameDropMode {
   LIVE_EDIT_CURRENTLY_SET_MODE
 };
 
-enum class UnicodeEncoding : uint8_t {
-  // Different unicode encodings in a |word32|:
-  UTF16,  // hi 16bits -> trailing surrogate or 0, low 16bits -> lead surrogate
-  UTF32,  // full UTF32 code unit / Unicode codepoint
-};
-
-inline size_t hash_value(UnicodeEncoding encoding) {
-  return static_cast<uint8_t>(encoding);
-}
-
-inline std::ostream& operator<<(std::ostream& os, UnicodeEncoding encoding) {
-  switch (encoding) {
-    case UnicodeEncoding::UTF16:
-      return os << "UTF16";
-    case UnicodeEncoding::UTF32:
-      return os << "UTF32";
-  }
-  UNREACHABLE();
-  return os;
-}
-
 }  // namespace internal
 }  // namespace v8
 

src/objects.h

@@ -7106,7 +7106,6 @@ enum BuiltinFunctionId {
   kTypedArrayByteOffset,
   kTypedArrayLength,
   kSharedArrayBufferByteLength,
-  kStringIteratorNext,
 };