Reland "[turbofan] Add simplified operator for String.prototype.codePointAt"

This is a reland of 22d894c8
Original change's description:
> [turbofan] Add simplified operator for String.prototype.codePointAt
> 
> This CL adds the simplified operators
>   StringCodePointAt
>   SeqStringCodePointAt
> and associated lowering.
> 
> Bug: v8:7270
> Change-Id: I5aeefddeec39c3119b2d225e92a3116f802e7b45
> Reviewed-on: https://chromium-review.googlesource.com/861789
> Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
> Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
> Reviewed-by: Peter Marshall <petermarshall@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#50547}

Bug: v8:7270
Change-Id: Ia08d18543fc165fc2312cd393ed51f4ec98d7a58
Reviewed-on: https://chromium-review.googlesource.com/866311Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50599}

src/builtins/builtins-definitions.h

@@ -91,8 +91,9 @@ namespace internal {
   ASM(StackCheck)                                                              \
                                                                                \
   /* String helpers */                                                         \
-  TFC(StringCharAt, StringCharAt, 1)                                           \
-  TFC(StringCharCodeAt, StringCharCodeAt, 1)                                   \
+  TFC(StringCharAt, StringAt, 1)                                               \
+  TFC(StringCharCodeAt, StringAt, 1)                                           \
+  TFC(StringCodePointAt, StringAt, 1)                                          \
   TFC(StringEqual, Compare, 1)                                                 \
   TFC(StringGreaterThan, Compare, 1)                                           \
   TFC(StringGreaterThanOrEqual, Compare, 1)                                    \

src/builtins/builtins-string-gen.cc

@@ -576,6 +576,21 @@ TF_BUILTIN(StringCharCodeAt, StringBuiltinsAssembler) {
   Return(result);
 }
 
+TF_BUILTIN(StringCodePointAt, StringBuiltinsAssembler) {
+  Node* receiver = Parameter(Descriptor::kReceiver);
+  Node* position = Parameter(Descriptor::kPosition);
+
+  // TODO(sigurds) Figure out if passing length as argument pays off.
+  TNode<IntPtrT> length = LoadStringLengthAsWord(receiver);
+  // Load the character code at the {position} from the {receiver}.
+  TNode<Int32T> code =
+      LoadSurrogatePairAt(receiver, length, position, UnicodeEncoding::UTF32);
+  // And return it as TaggedSigned value.
+  // TODO(turbofan): Allow builtins to return values untagged.
+  TNode<Smi> result = SmiFromWord32(code);
+  Return(result);
+}
+
 // -----------------------------------------------------------------------------
 // ES6 section 21.1 String Objects
 

src/compiler/effect-control-linearizer.cc

@@ -847,6 +847,12 @@ bool EffectControlLinearizer::TryWireInStateEffect(Node* node,
     case IrOpcode::kSeqStringCharCodeAt:
       result = LowerSeqStringCharCodeAt(node);
       break;
+    case IrOpcode::kStringCodePointAt:
+      result = LowerStringCodePointAt(node);
+      break;
+    case IrOpcode::kSeqStringCodePointAt:
+      result = LowerSeqStringCharCodeAt(node);
+      break;
     case IrOpcode::kStringToLowerCaseIntl:
       result = LowerStringToLowerCaseIntl(node);
       break;
@@ -2687,19 +2693,25 @@ Node* EffectControlLinearizer::LowerStringCharCodeAt(Node* node) {
                  __ NoContextConstant());
 }
 
-Node* EffectControlLinearizer::LowerSeqStringCharCodeAt(Node* node) {
+Node* EffectControlLinearizer::LowerStringCodePointAt(Node* node) {
   Node* receiver = node->InputAt(0);
   Node* position = node->InputAt(1);
 
+  Callable const callable =
+      Builtins::CallableFor(isolate(), Builtins::kStringCodePointAt);
+  Operator::Properties properties = Operator::kNoThrow | Operator::kNoWrite;
+  CallDescriptor::Flags flags = CallDescriptor::kNoFlags;
+  CallDescriptor* desc = Linkage::GetStubCallDescriptor(
+      isolate(), graph()->zone(), callable.descriptor(), 0, flags, properties,
+      MachineType::TaggedSigned());
+  return __ Call(desc, __ HeapConstant(callable.code()), receiver, position,
+                 __ NoContextConstant());
+}
+
+Node* EffectControlLinearizer::LoadFromString(Node* receiver, Node* position,
+                                              Node* is_one_byte) {
   auto one_byte_load = __ MakeLabel();
   auto done = __ MakeLabel(MachineRepresentation::kWord32);
-
-  Node* map = __ LoadField(AccessBuilder::ForMap(), receiver);
-  Node* instance_type = __ LoadField(AccessBuilder::ForMapInstanceType(), map);
-  Node* is_one_byte = __ Word32Equal(
-      __ Word32And(instance_type, __ Int32Constant(kStringEncodingMask)),
-      __ Int32Constant(kOneByteStringTag));
-
   __ GotoIf(is_one_byte, &one_byte_load);
   Node* two_byte_result = __ LoadElement(
       AccessBuilder::ForSeqTwoByteStringCharacter(), receiver, position);
@@ -2714,6 +2726,85 @@ Node* EffectControlLinearizer::LowerSeqStringCharCodeAt(Node* node) {
   return done.PhiAt(0);
 }
 
+Node* EffectControlLinearizer::LowerSeqStringCharCodeAt(Node* node) {
+  Node* receiver = node->InputAt(0);
+  Node* position = node->InputAt(1);
+
+  Node* map = __ LoadField(AccessBuilder::ForMap(), receiver);
+  Node* instance_type = __ LoadField(AccessBuilder::ForMapInstanceType(), map);
+  Node* is_one_byte = __ Word32Equal(
+      __ Word32And(instance_type, __ Int32Constant(kStringEncodingMask)),
+      __ Int32Constant(kOneByteStringTag));
+
+  return LoadFromString(receiver, position, is_one_byte);
+}
+
+Node* EffectControlLinearizer::LowerSeqStringCodePointAt(
+    Node* node, UnicodeEncoding encoding) {
+  Node* receiver = node->InputAt(0);
+  Node* position = node->InputAt(1);
+
+  Node* map = __ LoadField(AccessBuilder::ForMap(), receiver);
+  Node* instance_type = __ LoadField(AccessBuilder::ForMapInstanceType(), map);
+  Node* is_one_byte = __ Word32Equal(
+      __ Word32And(instance_type, __ Int32Constant(kStringEncodingMask)),
+      __ Int32Constant(kOneByteStringTag));
+
+  Node* first_char_code = LoadFromString(receiver, position, is_one_byte);
+
+  auto return_result = __ MakeLabel(MachineRepresentation::kWord32);
+
+  // Check if first character code is outside of interval [0xD800, 0xDBFF].
+  Node* first_out =
+      __ Word32Equal(__ Word32And(first_char_code, __ Int32Constant(0xFC00)),
+                     __ Int32Constant(0xD800));
+  // Return first character code.
+  __ GotoIf(first_out, &return_result, first_char_code);
+  // Check if position + 1 is still in range.
+  Node* length = __ LoadField(AccessBuilder::ForStringLength(), receiver);
+  Node* next_position = __ Int32Add(position, __ Int32Constant(1));
+  Node* next_position_in_range = __ Int32LessThan(next_position, length);
+  __ GotoIf(next_position_in_range, &return_result, first_char_code);
+
+  // Load second character code.
+  Node* second_char_code = LoadFromString(receiver, next_position, is_one_byte);
+  // Check if first character code is outside of interval [0xD800, 0xDBFF].
+  Node* second_out =
+      __ Word32Equal(__ Word32And(second_char_code, __ Int32Constant(0xFC00)),
+                     __ Int32Constant(0xDC00));
+  __ GotoIfNot(second_out, &return_result, first_char_code);
+
+  Node* result;
+  switch (encoding) {
+    case UnicodeEncoding::UTF16:
+      result = __ Word32Or(
+// Need to swap the order for big-endian platforms
+#if V8_TARGET_BIG_ENDIAN
+          __ Word32Shl(first_char_code, __ Int32Constant(16)),
+          second_char_code);
+#else
+          __ Word32Shl(second_char_code, __ Int32Constant(16)),
+          first_char_code);
+#endif
+      break;
+    case UnicodeEncoding::UTF32: {
+      // Convert UTF16 surrogate pair into |word32| code point, encoded as
+      // UTF32.
+      Node* surrogate_offset =
+          __ Int32Constant(0x10000 - (0xD800 << 10) - 0xDC00);
+
+      // (lead << 10) + trail + SURROGATE_OFFSET
+      result = __ Int32Add(__ Word32Shl(first_char_code, __ Int32Constant(10)),
+                           __ Int32Add(second_char_code, surrogate_offset));
+      break;
+    }
+  }
+  __ Goto(&return_result, result);
+
+  __ Bind(&return_result);
+  return return_result.PhiAt(0);
+}
+
 Node* EffectControlLinearizer::LowerStringFromCharCode(Node* node) {
   Node* value = node->InputAt(0);
 

src/compiler/effect-control-linearizer.h

@@ -118,6 +118,8 @@ class V8_EXPORT_PRIVATE EffectControlLinearizer {
   Node* LowerStringCharAt(Node* node);
   Node* LowerStringCharCodeAt(Node* node);
   Node* LowerSeqStringCharCodeAt(Node* node);
+  Node* LowerStringCodePointAt(Node* node);
+  Node* LowerSeqStringCodePointAt(Node* node, UnicodeEncoding encoding);
   Node* LowerStringToLowerCaseIntl(Node* node);
   Node* LowerStringToUpperCaseIntl(Node* node);
   Node* LowerStringFromCharCode(Node* node);
@@ -179,6 +181,7 @@ class V8_EXPORT_PRIVATE EffectControlLinearizer {
   Node* ChangeSmiToIntPtr(Node* value);
   Node* ChangeSmiToInt32(Node* value);
   Node* ObjectIsSmi(Node* value);
+  Node* LoadFromString(Node* receiver, Node* position, Node* is_one_byte);
 
   Node* SmiMaxValueConstant();
   Node* SmiShiftBitsConstant();

src/compiler/opcodes.h

@@ -333,6 +333,8 @@
   V(StringCharAt)                       \
   V(StringCharCodeAt)                   \
   V(SeqStringCharCodeAt)                \
+  V(StringCodePointAt)                  \
+  V(SeqStringCodePointAt)               \
   V(StringFromCharCode)                 \
   V(StringFromCodePoint)                \
   V(StringIndexOf)                      \

src/compiler/simplified-lowering.cc

@@ -2353,6 +2353,22 @@ class RepresentationSelector {
         }
         return;
       }
+      case IrOpcode::kStringCodePointAt: {
+        Type* string_type = TypeOf(node->InputAt(0));
+        if (string_type->Is(Type::SeqString())) {
+          VisitBinop(node, UseInfo::AnyTagged(), UseInfo::TruncatingWord32(),
+                     MachineRepresentation::kWord32);
+          if (lower()) {
+            NodeProperties::ChangeOp(node,
+                                     simplified()->SeqStringCodePointAt());
+          }
+        } else {
+          // TODO(turbofan): Allow builtins to return untagged values.
+          VisitBinop(node, UseInfo::AnyTagged(), UseInfo::TruncatingWord32(),
+                     MachineRepresentation::kTaggedSigned);
+        }
+        return;
+      }
       case IrOpcode::kStringFromCharCode: {
         VisitUnop(node, UseInfo::TruncatingWord32(),
                   MachineRepresentation::kTaggedPointer);

src/compiler/simplified-operator.cc

@@ -657,6 +657,8 @@ bool operator==(CheckMinusZeroParameters const& lhs,
   V(StringCharAt, Operator::kNoProperties, 2, 1)                 \
   V(StringCharCodeAt, Operator::kNoProperties, 2, 1)             \
   V(SeqStringCharCodeAt, Operator::kNoProperties, 2, 1)          \
+  V(StringCodePointAt, Operator::kNoProperties, 2, 1)            \
+  V(SeqStringCodePointAt, Operator::kNoProperties, 2, 1)         \
   V(StringFromCharCode, Operator::kNoProperties, 1, 0)           \
   V(StringIndexOf, Operator::kNoProperties, 3, 0)                \
   V(StringLength, Operator::kNoProperties, 1, 0)                 \

src/compiler/simplified-operator.h

@@ -503,6 +503,8 @@ class V8_EXPORT_PRIVATE SimplifiedOperatorBuilder final
   const Operator* StringCharAt();
   const Operator* StringCharCodeAt();
   const Operator* SeqStringCharCodeAt();
+  const Operator* StringCodePointAt();
+  const Operator* SeqStringCodePointAt();
   const Operator* StringFromCharCode();
   const Operator* StringFromCodePoint(UnicodeEncoding encoding);
   const Operator* StringIndexOf();

src/compiler/typer.cc

@@ -1948,6 +1948,14 @@ Type* Typer::Visitor::TypeSeqStringCharCodeAt(Node* node) {
   return typer_->cache_.kUint16;
 }
 
+Type* Typer::Visitor::TypeStringCodePointAt(Node* node) {
+  return Type::Range(0.0, String::kMaxCodePoint, zone());
+}
+
+Type* Typer::Visitor::TypeSeqStringCodePointAt(Node* node) {
+  return Type::Range(0.0, String::kMaxCodePoint, zone());
+}
+
 Type* Typer::Visitor::TypeStringFromCharCode(Node* node) {
   return TypeUnaryOp(node, StringFromCharCodeTyper);
 }

src/compiler/verifier.cc

@@ -1054,6 +1054,18 @@ void Verifier::Visitor::Check(Node* node, const AllNodes& all) {
       CheckValueInputIs(node, 1, Type::Unsigned32());
       CheckTypeIs(node, Type::UnsignedSmall());
       break;
+    case IrOpcode::kStringCodePointAt:
+      // (String, Unsigned32) -> UnsignedSmall
+      CheckValueInputIs(node, 0, Type::String());
+      CheckValueInputIs(node, 1, Type::Unsigned32());
+      CheckTypeIs(node, Type::UnsignedSmall());
+      break;
+    case IrOpcode::kSeqStringCodePointAt:
+      // (String, Unsigned32) -> UnsignedSmall
+      CheckValueInputIs(node, 0, Type::String());
+      CheckValueInputIs(node, 1, Type::Unsigned32());
+      CheckTypeIs(node, Type::UnsignedSmall());
+      break;
     case IrOpcode::kStringFromCharCode:
       // Number -> String
       CheckValueInputIs(node, 0, Type::Number());

src/interface-descriptors.cc

@@ -269,21 +269,7 @@ void StoreNamedTransitionDescriptor::InitializePlatformSpecific(
   data->InitializePlatformSpecific(len, registers);
 }
 
-void StringCharAtDescriptor::InitializePlatformIndependent(
-    CallInterfaceDescriptorData* data) {
-  // kReceiver, kPosition
-  MachineType machine_types[] = {MachineType::AnyTagged(),
-                                 MachineType::IntPtr()};
-  data->InitializePlatformIndependent(arraysize(machine_types), 0,
-                                      machine_types);
-}
-
-void StringCharAtDescriptor::InitializePlatformSpecific(
-    CallInterfaceDescriptorData* data) {
-  DefaultInitializePlatformSpecific(data, kParameterCount);
-}
-
-void StringCharCodeAtDescriptor::InitializePlatformIndependent(
+void StringAtDescriptor::InitializePlatformIndependent(
     CallInterfaceDescriptorData* data) {
   // kReceiver, kPosition
   // TODO(turbofan): Allow builtins to return untagged values.
@@ -293,7 +279,7 @@ void StringCharCodeAtDescriptor::InitializePlatformIndependent(
                                       machine_types);
 }
 
-void StringCharCodeAtDescriptor::InitializePlatformSpecific(
+void StringAtDescriptor::InitializePlatformSpecific(
     CallInterfaceDescriptorData* data) {
   DefaultInitializePlatformSpecific(data, kParameterCount);
 }

src/interface-descriptors.h

@@ -62,8 +62,7 @@ class PlatformInterfaceDescriptor;
   V(Compare)                          \
   V(BinaryOp)                         \
   V(StringAdd)                        \
-  V(StringCharAt)                     \
-  V(StringCharCodeAt)                 \
+  V(StringAt)                         \
   V(ForInPrepare)                     \
   V(GetProperty)                      \
   V(ArgumentAdaptor)                  \
@@ -762,17 +761,12 @@ class StringAddDescriptor : public CallInterfaceDescriptor {
   DECLARE_DESCRIPTOR(StringAddDescriptor, CallInterfaceDescriptor)
 };
 
-class StringCharAtDescriptor final : public CallInterfaceDescriptor {
+// This desciptor is shared among String.p.charAt/charCodeAt/codePointAt
+// as they all have the same interface.
+class StringAtDescriptor final : public CallInterfaceDescriptor {
  public:
   DEFINE_PARAMETERS(kReceiver, kPosition)
-  DECLARE_DESCRIPTOR_WITH_CUSTOM_FUNCTION_TYPE(StringCharAtDescriptor,
-                                               CallInterfaceDescriptor)
-};
-
-class StringCharCodeAtDescriptor final : public CallInterfaceDescriptor {
- public:
-  DEFINE_PARAMETERS(kReceiver, kPosition)
-  DECLARE_DESCRIPTOR_WITH_CUSTOM_FUNCTION_TYPE(StringCharCodeAtDescriptor,
+  DECLARE_DESCRIPTOR_WITH_CUSTOM_FUNCTION_TYPE(StringAtDescriptor,
                                                CallInterfaceDescriptor)
 };