[builtin] Fast paths for Array.concat

- Initial implementation of Array.concat on Torque.
- Adds fast paths for `[].concat()` and `x.concat()`, these are now
  as fast as `[...x]` and `x.slice()` for non-optimised code.

Bug: v8:7152
Change-Id: I86ca15e4e1e67f53424ef0c8bb7eea12d7e660b3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3026716
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Victor Gomes <victorgomes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75737}

BUILD.bazel

@@ -610,6 +610,7 @@ filegroup(
     srcs = [
         "src/builtins/aggregate-error.tq",
         "src/builtins/array-at.tq",
+        "src/builtins/array-concat.tq",
         "src/builtins/array-copywithin.tq",
         "src/builtins/array-every.tq",
         "src/builtins/array-filter.tq",

BUILD.gn

@@ -1396,6 +1396,7 @@ action("postmortem-metadata") {
 torque_files = [
   "src/builtins/aggregate-error.tq",
   "src/builtins/array-at.tq",
+  "src/builtins/array-concat.tq",
   "src/builtins/array-copywithin.tq",
   "src/builtins/array-every.tq",
   "src/builtins/array-filter.tq",

src/builtins/array-concat.tq

@@ -0,0 +1,49 @@
+// Copyright 2021 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.
+
+namespace array {
+
+extern builtin ArrayConcat(Context, JSFunction, JSAny, int32): JSAny;
+
+transitioning javascript builtin
+ArrayPrototypeConcat(
+    js-implicit context: NativeContext, receiver: JSAny)(...arguments): JSAny {
+  // Fast path if we invoke as `x.concat()`.
+  if (arguments.length == 0) {
+    typeswitch (receiver) {
+      case (a: FastJSArrayForCopy): {
+        return CloneFastJSArray(context, a);
+      }
+      case (JSAny): {
+        // Fallthrough.
+      }
+    }
+  }
+
+  // Fast path if we invoke as `[].concat(x)`.
+  try {
+    const receiverAsArray: FastJSArrayForConcat =
+        Cast<FastJSArrayForConcat>(receiver)
+        otherwise ReceiverIsNotFastJSArrayForConcat;
+    if (receiverAsArray.IsEmpty() && arguments.length == 1) {
+      typeswitch (arguments[0]) {
+        case (a: FastJSArrayForCopy): {
+          return CloneFastJSArray(context, a);
+        }
+        case (JSAny): {
+          // Fallthrough.
+        }
+      }
+    }
+  } label ReceiverIsNotFastJSArrayForConcat {
+    // Fallthrough.
+  }
+
+  // TODO(victorgomes): Implement slow path ArrayConcat in Torque.
+  tail ArrayConcat(
+      context, LoadTargetFromFrame(), Undefined,
+      Convert<int32>(arguments.length));
+}
+
+}  // namespace array

src/builtins/base.tq

@@ -1198,6 +1198,7 @@ extern macro IsPrototypeInitialArrayPrototype(implicit context: Context)(Map):
 extern macro IsNoElementsProtectorCellInvalid(): bool;
 extern macro IsArrayIteratorProtectorCellInvalid(): bool;
 extern macro IsArraySpeciesProtectorCellInvalid(): bool;
+extern macro IsIsConcatSpreadableProtectorCellInvalid(): bool;
 extern macro IsTypedArraySpeciesProtectorCellInvalid(): bool;
 extern macro IsPromiseSpeciesProtectorCellInvalid(): bool;
 extern macro IsMockArrayBufferAllocatorFlag(): bool;

src/builtins/cast.tq

@@ -551,6 +551,15 @@ Cast<FastJSArrayForCopy>(implicit context: Context)(o: HeapObject):
   return %RawDownCast<FastJSArrayForCopy>(a);
 }
 
+Cast<FastJSArrayForConcat>(implicit context: Context)(o: HeapObject):
+    FastJSArrayForConcat
+    labels CastError {
+  if (IsArraySpeciesProtectorCellInvalid()) goto CastError;
+  if (IsIsConcatSpreadableProtectorCellInvalid()) goto CastError;
+  const a = Cast<FastJSArrayForRead>(o) otherwise CastError;
+  return %RawDownCast<FastJSArrayForConcat>(a);
+}
+
 Cast<FastJSArrayWithNoCustomIteration>(implicit context: Context)(
     o: HeapObject): FastJSArrayWithNoCustomIteration
     labels CastError {

src/codegen/code-stub-assembler.cc

@@ -6195,6 +6195,13 @@ TNode<BoolT> CodeStubAssembler::IsArraySpeciesProtectorCellInvalid() {
   return TaggedEqual(cell_value, invalid);
 }
 
+TNode<BoolT> CodeStubAssembler::IsIsConcatSpreadableProtectorCellInvalid() {
+  TNode<Smi> invalid = SmiConstant(Protectors::kProtectorInvalid);
+  TNode<PropertyCell> cell = IsConcatSpreadableProtectorConstant();
+  TNode<Object> cell_value = LoadObjectField(cell, PropertyCell::kValueOffset);
+  return TaggedEqual(cell_value, invalid);
+}
+
 TNode<BoolT> CodeStubAssembler::IsTypedArraySpeciesProtectorCellInvalid() {
   TNode<Smi> invalid = SmiConstant(Protectors::kProtectorInvalid);
   TNode<PropertyCell> cell = TypedArraySpeciesProtectorConstant();

src/codegen/code-stub-assembler.h

@@ -68,6 +68,8 @@ enum class PrimitiveType { kBoolean, kNumber, kString, kSymbol };
     AsyncGeneratorYieldResolveSharedFun)                                       \
   V(AsyncIteratorValueUnwrapSharedFun, async_iterator_value_unwrap_shared_fun, \
     AsyncIteratorValueUnwrapSharedFun)                                         \
+  V(IsConcatSpreadableProtector, is_concat_spreadable_protector,               \
+    IsConcatSpreadableProtector)                                               \
   V(MapIteratorProtector, map_iterator_protector, MapIteratorProtector)        \
   V(NoElementsProtector, no_elements_protector, NoElementsProtector)           \
   V(MegaDOMProtector, mega_dom_protector, MegaDOMProtector)                    \
@@ -2546,6 +2548,7 @@ class V8_EXPORT_PRIVATE CodeStubAssembler
   TNode<BoolT> IsPromiseResolveProtectorCellInvalid();
   TNode<BoolT> IsPromiseThenProtectorCellInvalid();
   TNode<BoolT> IsArraySpeciesProtectorCellInvalid();
+  TNode<BoolT> IsIsConcatSpreadableProtectorCellInvalid();
   TNode<BoolT> IsTypedArraySpeciesProtectorCellInvalid();
   TNode<BoolT> IsRegExpSpeciesProtectorCellInvalid();
   TNode<BoolT> IsPromiseSpeciesProtectorCellInvalid();

src/debug/debug-evaluate.cc

@@ -560,6 +560,7 @@ DebugInfo::SideEffectState BuiltinGetSideEffectState(Builtin id) {
     case Builtin::kArrayPrototypeValues:
     case Builtin::kArrayIncludes:
     case Builtin::kArrayPrototypeAt:
+    case Builtin::kArrayPrototypeConcat:
     case Builtin::kArrayPrototypeEntries:
     case Builtin::kArrayPrototypeFill:
     case Builtin::kArrayPrototypeFind:

src/init/bootstrapper.cc

@@ -1741,8 +1741,8 @@ void Genesis::InitializeGlobal(Handle<JSGlobalObject> global_object,
     JSObject::AddProperty(isolate_, proto, factory->constructor_string(),
                           array_function, DONT_ENUM);
 
-    SimpleInstallFunction(isolate_, proto, "concat", Builtin::kArrayConcat, 1,
-                          false);
+    SimpleInstallFunction(isolate_, proto, "concat",
+                          Builtin::kArrayPrototypeConcat, 1, false);
     SimpleInstallFunction(isolate_, proto, "copyWithin",
                           Builtin::kArrayPrototypeCopyWithin, 2, false);
     SimpleInstallFunction(isolate_, proto, "fill", Builtin::kArrayPrototypeFill,

src/objects/js-array.tq

@@ -66,6 +66,10 @@ transient type FastJSArrayForRead extends JSArray;
 // A FastJSArray when the global ArraySpeciesProtector is not invalidated.
 transient type FastJSArrayForCopy extends FastJSArray;
 
+// A FastJSArray when the global ArraySpeciesProtector and
+// IsConcatSpreadableProtector are not invalidated.
+transient type FastJSArrayForConcat extends FastJSArrayForRead;
+
 // A FastJSArray when the global ArrayIteratorProtector is not invalidated.
 transient type FastJSArrayWithNoCustomIteration extends FastJSArray;