[builtins] Implement Array.prototype.slice in Torque

In the process:

- add volatile types for FastJSArray and remove the length_fast accessor
  from JSArray with the application of more rigorous typing.
- add micro benchmarks for testing all the interesting slice cases

Also update a few assorted places in .tq code to make them more
idiomatic.

Change-Id: I76ec2bb25b65a869180af1f7288419dc1f0a9c37
Reviewed-on: https://chromium-review.googlesource.com/c/1281603
Commit-Queue: Daniel Clifford <danno@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56806}

BUILD.gn

@@ -917,6 +917,7 @@ torque_files = [
   "src/builtins/array-join.tq",
   "src/builtins/array-lastindexof.tq",
   "src/builtins/array-reverse.tq",
+  "src/builtins/array-slice.tq",
   "src/builtins/array-splice.tq",
   "src/builtins/array-unshift.tq",
   "src/builtins/typed-array.tq",

benchmarks/micro/slice-perf.js

@@ -0,0 +1,83 @@
+// Copyright 2018 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.
+
+const kIterations = 1000000;
+const kIterationShort = 10000;
+const kArraySize = 64;
+
+let smi_array = [];
+for (let i = 0; i < kArraySize; ++i) smi_array[i] = Math.floor(Math.random() * 100);
+
+let start = performance.now();
+for (let x = 0; x < kIterations; ++x) {
+  smi_array.slice(0);
+}
+let stop = performance.now();
+print("smi_array copy: " + (Math.floor((stop - start)*10)/10) + " ms");
+
+start = performance.now();
+for (let x = 0; x < kIterations; ++x) {
+  smi_array.slice(x % kArraySize);
+}
+stop = performance.now();
+print("smi_array: " + (Math.floor((stop - start)*10)/10) + " ms");
+
+let double_array = [];
+for (let i = 0; i < kArraySize; ++i) double_array[i] = Math.random() * 100;
+start = performance.now();
+for (let x = 0; x < kIterations; ++x) {
+  double_array.slice(x % kArraySize);
+}
+stop = performance.now();
+print("double_array: " + (Math.floor((stop - start)*10)/10) + " ms");
+
+let object_array = [];
+for (let i = 0; i < kArraySize; ++i) object_array[i] = new Object();
+start = performance.now();
+for (let x = 0; x < kIterations; ++x) {
+  object_array.slice(x % kArraySize);
+}
+stop = performance.now();
+print("object_array: " + (Math.floor((stop - start)*10)/10) + " ms");
+
+let dictionary_array = [];
+for (let i = 0; i < kArraySize; ++i) dictionary_array[i] = new Object();
+dictionary_array[100000] = new Object();
+start = performance.now();
+for (let x = 0; x < kIterationShort; ++x) {
+  dictionary_array.slice(x % kArraySize);
+}
+stop = performance.now();
+print("dictionary: " + (Math.floor((stop - start)*10)/10) + " ms");
+
+let arguments_array;
+function sloppy() {
+  arguments_array = arguments;
+}
+sloppy.apply(null, smi_array);
+start = performance.now();
+for (let x = 0; x < kIterations; ++x) {
+  let r = Array.prototype.slice.call(arguments_array, x % kArraySize);
+}
+stop = performance.now();
+print("arguments_array (sloppy): " + (Math.floor((stop - start)*10)/10) + " ms");
+
+function sloppy2 (a) {
+  arguments_array = arguments;
+}
+sloppy2.apply(null, smi_array);
+start = performance.now();
+for (let x = 0; x < kIterations; ++x) {
+  Array.prototype.slice.call(arguments_array, x % kArraySize);
+}
+stop = performance.now();
+print("arguments_array (fast aliased): " + (Math.floor((stop - start)*10)/10) + " ms");
+
+delete arguments_array[5];
+start = performance.now();
+for (let x = 0; x < kIterationShort; ++x) {
+  Array.prototype.slice.call(arguments_array, x % kArraySize);
+}
+stop = performance.now();
+print("arguments_array (slow aliased): " + (Math.floor((stop - start)*10)/10) + " ms");

src/bootstrapper.cc

@@ -1739,8 +1739,8 @@ void Genesis::InitializeGlobal(Handle<JSGlobalObject> global_object,
                           Builtins::kArrayPrototypeShift, 0, false);
     SimpleInstallFunction(isolate_, proto, "unshift",
                           Builtins::kArrayPrototypeUnshift, 1, false);
-    SimpleInstallFunction(isolate_, proto, "slice",
-                          Builtins::kArrayPrototypeSlice, 2, false);
+    SimpleInstallFunction(isolate_, proto, "slice", Builtins::kArraySlice, 2,
+                          false);
     SimpleInstallFunction(isolate_, proto, "sort",
                           Builtins::kArrayPrototypeSort, 1, false);
     SimpleInstallFunction(isolate_, proto, "splice", Builtins::kArraySplice, 2,

src/builtins/array-lastindexof.tq

@@ -75,10 +75,8 @@ module array {
       context: Context, receiver: JSReceiver, searchElement: Object,
       from: Number): Object
       labels Slow {
-    EnsureFastJSArray(context, receiver) otherwise Slow;
-    const array: JSArray = UnsafeCast<JSArray>(receiver);
-
-    const length: Smi = array.length_fast;
+    const array: FastJSArray = Cast<FastJSArray>(receiver) otherwise Slow;
+    const length: Smi = array.length;
     if (length == 0) return SmiConstant(-1);
 
     const fromSmi: Smi = Cast<Smi>(from) otherwise Slow;

src/builtins/array-reverse.tq

@@ -143,21 +143,22 @@ module array {
     return object;
   }
 
-  macro TryFastPackedArrayReverse(receiver: Object) labels Slow {
-    const array: JSArray = Cast<JSArray>(receiver) otherwise Slow;
+  macro TryFastPackedArrayReverse(implicit context: Context)(receiver: Object)
+  labels Slow {
+    const array: FastJSArray = Cast<FastJSArray>(receiver) otherwise Slow;
 
     const kind: ElementsKind = array.map.elements_kind;
     if (kind == PACKED_SMI_ELEMENTS) {
       EnsureWriteableFastElements(array);
       FastPackedArrayReverse<FastPackedSmiElements, Smi>(
-          array.elements, array.length_fast);
+          array.elements, array.length);
     } else if (kind == PACKED_ELEMENTS) {
       EnsureWriteableFastElements(array);
       FastPackedArrayReverse<FastPackedObjectElements, Object>(
-          array.elements, array.length_fast);
+          array.elements, array.length);
     } else if (kind == PACKED_DOUBLE_ELEMENTS) {
       FastPackedArrayReverse<FastPackedDoubleElements, float64>(
-          array.elements, array.length_fast);
+          array.elements, array.length);
     } else {
       goto Slow;
     }

src/builtins/array-slice.tq

@@ -0,0 +1,208 @@
+// Copyright 2018 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.
+
+module array {
+  macro HandleSimpleArgumentsSlice(
+      context: Context, args: JSArgumentsObjectWithLength, start: Smi,
+      count: Smi): JSArray
+      labels Bailout {
+    const end: Smi = start + count;
+    const sourceElements: FixedArray =
+        Cast<FixedArray>(args.elements) otherwise Bailout;
+    if (SmiAbove(end, sourceElements.length)) goto Bailout;
+
+    const arrayMap: Map = LoadJSArrayElementsMap(HOLEY_ELEMENTS, context);
+    const result: JSArray =
+        AllocateJSArray(HOLEY_ELEMENTS, arrayMap, count, count);
+    const newElements: FixedArray =
+        Cast<FixedArray>(result.elements) otherwise Bailout;
+    CopyElements(
+        PACKED_ELEMENTS, newElements, Convert<intptr>(0), sourceElements,
+        Convert<intptr>(start), Convert<intptr>(count));
+    return result;
+  }
+
+  macro HandleFastAliasedSloppyArgumentsSlice(
+      context: Context, args: JSArgumentsObjectWithLength, start: Smi,
+      count: Smi): JSArray
+      labels Bailout {
+    const sloppyElements: SloppyArgumentsElements =
+        Cast<SloppyArgumentsElements>(args.elements) otherwise Bailout;
+    const sloppyElementsLength: Smi = sloppyElements.length;
+    const parameterMapLength: Smi =
+        sloppyElementsLength - kSloppyArgumentsParameterMapStart;
+
+    // Check to make sure that the extraction will not access outside the
+    // defined arguments
+    const end: Smi = start + count;
+    const unmappedElements: FixedArray =
+        Cast<FixedArray>(sloppyElements[kSloppyArgumentsArgumentsIndex])
+        otherwise Bailout;
+    const unmappedElementsLength: Smi = unmappedElements.length;
+    if (SmiAbove(end, unmappedElementsLength)) goto Bailout;
+
+    const argumentsContext: Context =
+        UnsafeCast<Context>(sloppyElements[kSloppyArgumentsContextIndex]);
+
+    const arrayMap: Map = LoadJSArrayElementsMap(HOLEY_ELEMENTS, context);
+    const result: JSArray =
+        AllocateJSArray(HOLEY_ELEMENTS, arrayMap, count, count);
+
+    let indexOut: Smi = 0;
+    const resultElements: FixedArray = UnsafeCast<FixedArray>(result.elements);
+    const to: Smi = SmiMin(parameterMapLength, end);
+
+    // Fill in the part of the result that map to context-mapped parameters.
+    for (let current: Smi = start; current < to; ++current) {
+      const e: Object =
+          sloppyElements[current + kSloppyArgumentsParameterMapStart];
+      const newElement: Object = e != Hole ?
+          argumentsContext[UnsafeCast<Smi>(e)] :
+          unmappedElements[current];
+      StoreFixedArrayElementSmi(
+          resultElements, indexOut++, newElement, SKIP_WRITE_BARRIER);
+    }
+
+    // Fill in the rest of the result that contains the unmapped parameters
+    // above the formal parameters.
+    const unmappedFrom: Smi = SmiMin(SmiMax(parameterMapLength, start), end);
+    const restCount: Smi = end - unmappedFrom;
+    CopyElements(
+        PACKED_ELEMENTS, resultElements, Convert<intptr>(indexOut),
+        unmappedElements, Convert<intptr>(unmappedFrom),
+        Convert<intptr>(restCount));
+    return result;
+  }
+
+  macro HandleFastSlice(
+      context: Context, o: Object, startNumber: Number, countNumber: Number):
+      JSArray
+      labels Bailout {
+    const start: Smi = Cast<Smi>(startNumber) otherwise Bailout;
+    const count: Smi = Cast<Smi>(countNumber) otherwise Bailout;
+    assert(start >= 0);
+
+    // If the resulting array doesn't fit in new space, use the slow path.
+    if (count >= kMaxNewSpaceFixedArrayElements) goto Bailout;
+
+    typeswitch (o) {
+      case (a: FastJSArrayForCopy): {
+        // It's possible to modify the array length from a valueOf
+        // callback between the original array length read and this
+        // point. That can change the length of the array backing store,
+        // in the worst case, making it smaller than the region that needs
+        // to be copied out. Therefore, re-check the length before calling
+        // the appropriate fast path. See regress-785804.js
+        if (SmiAbove(start + count, a.length)) goto Bailout;
+        return ExtractFastJSArray(context, a, start, count);
+      }
+      case (a: JSArgumentsObjectWithLength): {
+        const nativeContext: NativeContext = LoadNativeContext(context);
+        const map: Map = a.map;
+        if (IsFastAliasedArgumentsMap(map)) {
+          return HandleFastAliasedSloppyArgumentsSlice(context, a, start, count)
+              otherwise Bailout;
+        } else if (IsStrictArgumentsMap(map) || IsSloppyArgumentsMap(map)) {
+          return HandleSimpleArgumentsSlice(context, a, start, count)
+              otherwise Bailout;
+        }
+      }
+      case (Object): {
+      }
+    }
+    goto Bailout;
+  }
+
+  // https://tc39.github.io/ecma262/#sec-array.prototype.slice
+  javascript builtin ArraySlice(
+      context: Context, receiver: Object, ...arguments): Object {
+    // Handle array cloning case if the receiver is a fast array.
+    if (arguments.length == 0) {
+      typeswitch (receiver) {
+        case (a: FastJSArrayForCopy): {
+          return CloneFastJSArray(context, a);
+        }
+        case (Object): {
+        }
+      }
+    }
+
+    // 1. Let O be ? ToObject(this value).
+    const o: JSReceiver = ToObject_Inline(context, receiver);
+
+    // 2. Let len be ? ToLength(? Get(O, "length")).
+    const len: Number = GetLengthProperty(o);
+
+    // 3. Let relativeStart be ? ToInteger(start).
+    const start: Object = arguments[0];
+    const relativeStart: Number = ToInteger_Inline(context, start);
+
+    // 4. If relativeStart < 0, let k be max((len + relativeStart), 0);
+    //    else let k be min(relativeStart, len).
+    let k: Number = relativeStart < 0 ? Max((len + relativeStart), 0) :
+                                        Min(relativeStart, len);
+
+    // 5. If end is undefined, let relativeEnd be len;
+    //    else let relativeEnd be ? ToInteger(end).
+    const end: Object = arguments[1];
+    const relativeEnd: Number =
+        end == Undefined ? len : ToInteger_Inline(context, end);
+
+    // 6. If relativeEnd < 0, let final be max((len + relativeEnd), 0);
+    //    else let final be min(relativeEnd, len).
+    const final: Number =
+        relativeEnd < 0 ? Max((len + relativeEnd), 0) : Min(relativeEnd, len);
+
+    // 7. Let count be max(final - k, 0).
+    const count: Number = Max(final - k, 0);
+
+    assert(0 <= k);
+    assert(k <= len);
+    assert(0 <= final);
+    assert(final <= len);
+    assert(0 <= count);
+    assert(count <= len);
+
+    try {
+      return HandleFastSlice(context, o, k, count) otherwise Slow;
+    }
+    label Slow {}
+
+    // 8. Let A be ? ArraySpeciesCreate(O, count).
+    const a: JSReceiver = ArraySpeciesCreate(context, o, count);
+
+    // 9. Let n be 0.
+    let n: Number = 0;
+
+    // 10. Repeat, while k < final
+    while (k < final) {
+      // a. Let Pk be ! ToString(k).
+      let pK: Number = k;
+
+      // b. Let kPresent be ? HasProperty(O, Pk).
+      const fromPresent: Boolean = HasProperty(o, pK);
+
+      // c. If kPresent is true, then
+      if (fromPresent == True) {
+        // i. Let kValue be ? Get(O, Pk).
+        const kValue: Object = GetProperty(o, pK);
+
+        // ii. Perform ? CreateDataPropertyOrThrow(A, ! ToString(n), kValue).
+        CreateDataProperty(a, n, kValue);
+      }
+
+      // d. Increase k by 1.
+      k++;
+
+      // e. Increase n by 1.
+      n++;
+    }
+
+    // 11. Perform ? Set(A, "length", n, true).
+    SetProperty(a, kLengthString, n);
+
+    // 12. Return A.
+    return a;
+  }
+}

src/builtins/array-unshift.tq

@@ -9,8 +9,7 @@ module array {
       context: Context, receiver: Object, arguments: constexpr Arguments):
       never
       labels Slow {
-    EnsureFastJSArray(context, receiver) otherwise Slow;
-    const array: JSArray = UnsafeCast<JSArray>(receiver);
+    const array: FastJSArray = Cast<FastJSArray>(receiver) otherwise Slow;
     EnsureWriteableFastElements(array);
 
     const map: Map = array.map;

src/builtins/array.tq

@@ -24,7 +24,7 @@ module array {
     // extract FixedArrays and don't have to worry about FixedDoubleArrays.
     assert(IsFastSmiOrTaggedElementsKind(array.map.elements_kind));
 
-    const length: Smi = array.length_fast;
+    const length: Smi = Cast<Smi>(array.length) otherwise unreachable;
     array.elements =
         ExtractFixedArray(elements, 0, length, length, kFixedArrays);
     assert(array.elements.map != kCOWMap);

src/builtins/base.tq

@@ -40,6 +40,10 @@ type JSArgumentsObjectWithLength extends JSObject
     generates 'TNode<JSArgumentsObjectWithLength>';
 type JSArray extends JSArgumentsObjectWithLength
     generates 'TNode<JSArray>';
+type FastJSArray extends JSArray
+    generates 'TNode<JSArray>';
+type FastJSArrayForCopy extends FastJSArray
+    generates 'TNode<JSArray>';
 type JSFunction extends JSObject generates 'TNode<JSFunction>';
 type JSBoundFunction extends JSObject generates 'TNode<JSBoundFunction>';
 type Callable = JSFunction|JSBoundFunction|JSProxy;
@@ -52,20 +56,14 @@ type FixedTypedArrayBase extends FixedArrayBase
     generates 'TNode<FixedTypedArrayBase>';
 type FixedTypedArray extends FixedTypedArrayBase
     generates 'TNode<FixedTypedArray>';
+type SloppyArgumentsElements extends FixedArray
+    generates 'TNode<FixedArray>';
 type NumberDictionary extends HeapObject
     generates 'TNode<NumberDictionary>';
 
 type NativeContextSlot generates 'TNode<IntPtrT>' constexpr 'int32_t';
 const ARRAY_JOIN_STACK_INDEX: constexpr NativeContextSlot
     generates 'Context::ARRAY_JOIN_STACK_INDEX';
-const FAST_ALIASED_ARGUMENTS_MAP_INDEX: constexpr NativeContextSlot
-    generates 'Context::FAST_ALIASED_ARGUMENTS_MAP_INDEX';
-const SLOW_ALIASED_ARGUMENTS_MAP_INDEX: constexpr NativeContextSlot
-    generates 'Context::SLOW_ALIASED_ARGUMENTS_MAP_INDEX';
-const STRICT_ARGUMENTS_MAP_INDEX: constexpr NativeContextSlot
-    generates 'Context::STRICT_ARGUMENTS_MAP_INDEX';
-const SLOPPY_ARGUMENTS_MAP_INDEX: constexpr NativeContextSlot
-    generates 'Context::SLOPPY_ARGUMENTS_MAP_INDEX';
 extern operator '[]' macro LoadContextElement(
     NativeContext, NativeContextSlot): Object;
 extern operator '[]=' macro StoreContextElement(
@@ -177,6 +175,18 @@ const kStringMaxLength: constexpr int31 generates 'String::kMaxLength';
 const kFixedArrayMaxLength:
     constexpr int31 generates 'FixedArray::kMaxLength';
 
+const kMaxRegularHeapObjectSize: constexpr int31
+    generates 'kMaxRegularHeapObjectSize';
+
+const kMaxNewSpaceFixedArrayElements: constexpr int31
+    generates 'FixedArray::kMaxRegularLength';
+const kSloppyArgumentsArgumentsIndex: constexpr int31
+    generates 'SloppyArgumentsElements::kArgumentsIndex';
+const kSloppyArgumentsContextIndex: constexpr int31
+    generates 'SloppyArgumentsElements::kContextIndex';
+const kSloppyArgumentsParameterMapStart: constexpr int31
+    generates 'SloppyArgumentsElements::kParameterMapStart';
+
 const kTruncateMinusZero: constexpr ToIntegerTruncationMode
     generates 'ToIntegerTruncationMode::kTruncateMinusZero';
 
@@ -308,6 +318,11 @@ extern macro IsElementsKindGreaterThan(
 extern macro IsFastElementsKind(constexpr ElementsKind): constexpr bool;
 extern macro IsDoubleElementsKind(constexpr ElementsKind): constexpr bool;
 
+extern macro IsFastAliasedArgumentsMap(implicit context: Context)(Map): bool;
+extern macro IsSlowAliasedArgumentsMap(implicit context: Context)(Map): bool;
+extern macro IsSloppyArgumentsMap(implicit context: Context)(Map): bool;
+extern macro IsStrictArgumentsMap(implicit context: Context)(Map): bool;
+
 extern macro SmiAbove(Smi, Smi): bool;
 
 extern operator '==' macro WordEqual(intptr, intptr): bool;
@@ -442,6 +457,9 @@ extern macro HeapObjectToString(HeapObject): String
     labels CastError;
 extern macro HeapObjectToHeapNumber(HeapObject): HeapNumber
     labels CastError;
+extern macro HeapObjectToSloppyArgumentsElements(HeapObject):
+    SloppyArgumentsElements
+    labels CastError;
 extern macro TaggedToNumber(Object): Number
     labels CastError;
 
@@ -459,6 +477,10 @@ CastHeapObject<FixedDoubleArray>(o: HeapObject): FixedDoubleArray
     labels CastError {
   return HeapObjectToFixedDoubleArray(o) otherwise CastError;
 }
+CastHeapObject<SloppyArgumentsElements>(o: HeapObject): SloppyArgumentsElements
+    labels CastError {
+  return HeapObjectToSloppyArgumentsElements(o) otherwise CastError;
+}
 CastHeapObject<JSDataView>(o: HeapObject): JSDataView
     labels CastError {
   return HeapObjectToJSDataView(o) otherwise CastError;
@@ -766,17 +788,18 @@ UnsafeCast<String>(o: Object): String {
 // type check().
 extern macro RawCastObjectToJSArgumentsObjectWithLength(Object):
     JSArgumentsObjectWithLength;
+extern macro RawCastObjectToFastJSArray(Object): FastJSArray;
+extern macro RawCastObjectToFastJSArrayForCopy(Object): FastJSArrayForCopy;
 
 macro BranchIfJSArgumentsObjectWithLength(implicit context: Context)(o: Object):
     never
     labels True, False {
   const heapObject: HeapObject = Cast<HeapObject>(o) otherwise False;
   const map: Map = heapObject.map;
-  const nativeContext: NativeContext = LoadNativeContext(context);
-  if (map == nativeContext[FAST_ALIASED_ARGUMENTS_MAP_INDEX]) goto True;
-  if (map == nativeContext[SLOW_ALIASED_ARGUMENTS_MAP_INDEX]) goto True;
-  if (map == nativeContext[STRICT_ARGUMENTS_MAP_INDEX]) goto True;
-  if (map != nativeContext[SLOPPY_ARGUMENTS_MAP_INDEX]) goto False;
+  if (IsFastAliasedArgumentsMap(map)) goto True;
+  if (IsSloppyArgumentsMap(map)) goto True;
+  if (IsStrictArgumentsMap(map)) goto True;
+  if (!IsSlowAliasedArgumentsMap(map)) goto False;
   goto True;
 }
 
@@ -797,17 +820,59 @@ Cast<JSArgumentsObjectWithLength>(implicit context: Context)(o: Object):
   }
 }
 
+UnsafeCast<FastJSArray>(implicit context: Context)(o: Object): FastJSArray {
+  assert(BranchIfFastJSArrayForCopy(o, context));
+  return RawCastObjectToFastJSArray(o);
+}
+
+Cast<FastJSArray>(implicit context: Context)(o: Object): FastJSArray
+    labels CastError {
+  if (BranchIfFastJSArray(o, context)) {
+    return UnsafeCast<FastJSArray>(o);
+  } else {
+    goto CastError;
+  }
+}
+
+Cast<FastJSArray>(implicit context: Context)(ho: HeapObject): FastJSArray
+    labels CastError {
+  if (BranchIfFastJSArray(ho, context)) {
+    return UnsafeCast<FastJSArray>(ho);
+  } else {
+    goto CastError;
+  }
+}
+
+UnsafeCast<FastJSArrayForCopy>(implicit context: Context)(o: Object):
+    FastJSArrayForCopy {
+  assert(BranchIfFastJSArrayForCopy(o, context));
+  return RawCastObjectToFastJSArrayForCopy(o);
+}
+
+Cast<FastJSArrayForCopy>(implicit context: Context)(o: Object):
+    FastJSArrayForCopy
+    labels CastError {
+  if (BranchIfFastJSArrayForCopy(o, context)) {
+    return UnsafeCast<FastJSArrayForCopy>(o);
+  } else {
+    goto CastError;
+  }
+}
+
 const kCOWMap: Map = UnsafeCast<Map>(LoadRoot(kFixedCOWArrayMapRootIndex));
 const kEmptyFixedArray: FixedArrayBase =
     UnsafeCast<FixedArrayBase>(LoadRoot(kEmptyFixedArrayRootIndex));
 
 extern macro BranchIfFastJSArray(Object, Context): never
     labels Taken, NotTaken;
+extern macro BranchIfFastJSArrayForCopy(Object, Context): never
+    labels Taken, NotTaken;
 extern macro BranchIfNotFastJSArray(Object, Context): never
     labels Taken, NotTaken;
-
-macro EnsureFastJSArray(context: Context, object: Object) labels Bailout {
-  if (BranchIfNotFastJSArray(object, context)) goto Bailout;
+macro BranchIfNotFastJSArrayForCopy(implicit context: Context)(o: Object):
+    never
+    labels Taken, NotTaken {
+  BranchIfFastJSArrayForCopy(o, context) otherwise NotTaken, Taken;
 }
 
 extern macro IsPrototypeInitialArrayPrototype(Context, Map): bool;
@@ -832,7 +897,7 @@ extern operator '.length' macro LoadJSTypedArrayLength(JSTypedArray): Smi;
 extern operator '.length' macro LoadJSArrayLength(JSArray): Number;
 extern operator '.length' macro LoadJSArgumentsObjectWithLength(
     JSArgumentsObjectWithLength): Object;
-extern operator '.length_fast' macro LoadFastJSArrayLength(JSArray): Smi;
+extern operator '.length' macro LoadFastJSArrayLength(FastJSArray): Smi;
 extern operator '.length=' macro StoreJSArrayLength(JSArray, Smi);
 
 extern operator '.length' macro LoadFixedArrayBaseLength(FixedArrayBase): Smi;
@@ -944,6 +1009,7 @@ extern macro Call(
 extern macro Call(
     Context, Callable, Object, Object, Object, Object, Object, Object): Object;
 
+extern builtin CloneFastJSArray(Context, FastJSArrayForCopy): JSArray;
 extern macro ExtractFixedArray(FixedArrayBase, Smi, Smi, Smi): FixedArrayBase;
 extern macro ExtractFixedArray(
     FixedArrayBase, Smi, Smi, Smi,
@@ -1080,8 +1146,7 @@ macro GetLengthProperty(implicit context: Context)(o: Object): Number {
         return a.length;
       }
       case (a: JSArgumentsObjectWithLength): {
-        const length: Object = a.length;
-        return Cast<Smi>(length) otherwise goto ToLength(length);
+        goto ToLength(a.length);
       }
       case (Object): deferred {
         goto ToLength(GetProperty(o, kLengthString));

src/code-stub-assembler.cc

@@ -4674,7 +4674,8 @@ void CodeStubAssembler::CopyElements(ElementsKind kind,
   CSA_ASSERT(this, IntPtrLessThanOrEqual(
                        IntPtrAdd(src_index, length),
                        LoadAndUntagFixedArrayBaseLength(src_elements)));
-  CSA_ASSERT(this, WordNotEqual(dst_elements, src_elements));
+  CSA_ASSERT(this, Word32Or(WordNotEqual(dst_elements, src_elements),
+                            WordEqual(length, IntPtrConstant(0))));
 
   // The write barrier can be ignored if {dst_elements} is in new space, or if
   // the elements pointer is FixedDoubleArray.
@@ -5831,6 +5832,38 @@ TNode<BoolT> CodeStubAssembler::IsPrototypeTypedArrayPrototype(
   return WordEqual(proto_of_proto, typed_array_prototype);
 }
 
+TNode<BoolT> CodeStubAssembler::IsFastAliasedArgumentsMap(
+    TNode<Context> context, TNode<Map> map) {
+  TNode<Context> const native_context = LoadNativeContext(context);
+  TNode<Object> const arguments_map = LoadContextElement(
+      native_context, Context::FAST_ALIASED_ARGUMENTS_MAP_INDEX);
+  return WordEqual(arguments_map, map);
+}
+
+TNode<BoolT> CodeStubAssembler::IsSlowAliasedArgumentsMap(
+    TNode<Context> context, TNode<Map> map) {
+  TNode<Context> const native_context = LoadNativeContext(context);
+  TNode<Object> const arguments_map = LoadContextElement(
+      native_context, Context::SLOW_ALIASED_ARGUMENTS_MAP_INDEX);
+  return WordEqual(arguments_map, map);
+}
+
+TNode<BoolT> CodeStubAssembler::IsSloppyArgumentsMap(TNode<Context> context,
+                                                     TNode<Map> map) {
+  TNode<Context> const native_context = LoadNativeContext(context);
+  TNode<Object> const arguments_map =
+      LoadContextElement(native_context, Context::SLOPPY_ARGUMENTS_MAP_INDEX);
+  return WordEqual(arguments_map, map);
+}
+
+TNode<BoolT> CodeStubAssembler::IsStrictArgumentsMap(TNode<Context> context,
+                                                     TNode<Map> map) {
+  TNode<Context> const native_context = LoadNativeContext(context);
+  TNode<Object> const arguments_map =
+      LoadContextElement(native_context, Context::STRICT_ARGUMENTS_MAP_INDEX);
+  return WordEqual(arguments_map, map);
+}
+
 TNode<BoolT> CodeStubAssembler::TaggedIsCallable(TNode<Object> object) {
   return Select<BoolT>(
       TaggedIsSmi(object), [=] { return Int32FalseConstant(); },

src/code-stub-assembler.h

@@ -423,6 +423,14 @@ class V8_EXPORT_PRIVATE CodeStubAssembler : public compiler::CodeAssembler {
     return TNode<JSArgumentsObjectWithLength>::UncheckedCast(p_o);
   }
 
+  TNode<JSArray> RawCastObjectToFastJSArray(TNode<Object> p_o) {
+    return TNode<JSArray>::UncheckedCast(p_o);
+  }
+
+  TNode<JSArray> RawCastObjectToFastJSArrayForCopy(TNode<Object> p_o) {
+    return TNode<JSArray>::UncheckedCast(p_o);
+  }
+
   Node* MatchesParameterMode(Node* value, ParameterMode mode);
 
 #define PARAMETER_BINOP(OpName, IntPtrOpName, SmiOpName) \
@@ -1639,6 +1647,14 @@ class V8_EXPORT_PRIVATE CodeStubAssembler : public compiler::CodeAssembler {
     return UncheckedCast<FixedDoubleArray>(base);
   }
 
+  TNode<FixedArray> HeapObjectToSloppyArgumentsElements(TNode<HeapObject> base,
+                                                        Label* cast_fail) {
+    GotoIf(WordNotEqual(LoadMap(base),
+                        LoadRoot(RootIndex::kSloppyArgumentsElementsMap)),
+           cast_fail);
+    return UncheckedCast<FixedArray>(base);
+  }
+
   TNode<Int32T> ConvertElementsKindToInt(TNode<Int32T> elements_kind) {
     return UncheckedCast<Int32T>(elements_kind);
   }
@@ -2008,6 +2024,14 @@ class V8_EXPORT_PRIVATE CodeStubAssembler : public compiler::CodeAssembler {
                                                 SloppyTNode<Map> map);
   TNode<BoolT> IsPrototypeTypedArrayPrototype(SloppyTNode<Context> context,
                                               SloppyTNode<Map> map);
+
+  TNode<BoolT> IsFastAliasedArgumentsMap(TNode<Context> context,
+                                         TNode<Map> map);
+  TNode<BoolT> IsSlowAliasedArgumentsMap(TNode<Context> context,
+                                         TNode<Map> map);
+  TNode<BoolT> IsSloppyArgumentsMap(TNode<Context> context, TNode<Map> map);
+  TNode<BoolT> IsStrictArgumentsMap(TNode<Context> context, TNode<Map> map);
+
   TNode<BoolT> IsSequentialStringInstanceType(
       SloppyTNode<Int32T> instance_type);
   TNode<BoolT> IsUncachedExternalStringInstanceType(

src/compiler/js-call-reducer.cc

@@ -3439,6 +3439,7 @@ Reduction JSCallReducer::ReduceJSCall(Node* node,
     case Builtins::kArrayPrototypeShift:
       return ReduceArrayPrototypeShift(node);
     case Builtins::kArrayPrototypeSlice:
+    case Builtins::kArraySlice:
       return ReduceArrayPrototypeSlice(node);
     case Builtins::kArrayPrototypeEntries:
       return ReduceArrayIterator(node, IterationKind::kEntries);

src/debug/debug-evaluate.cc

@@ -384,6 +384,8 @@ bool BuiltinToIntrinsicHasNoSideEffect(Builtins::Name builtin_id,
   /* Arrays */                                                       \
   V(Builtins::kArrayFilter, W(CreateDataProperty))                   \
   V(Builtins::kArrayMap, W(CreateDataProperty))                      \
+  V(Builtins::kArraySlice,                                           \
+    W(CreateDataProperty) W(SetKeyedProperty) W(SetNamedProperty))   \
   V(Builtins::kArrayPrototypeSlice,                                  \
     W(CreateDataProperty) W(SetKeyedProperty) W(SetNamedProperty))   \
   /* TypedArrays */                                                  \
@@ -556,6 +558,7 @@ DebugInfo::SideEffectState BuiltinGetSideEffectState(Builtins::Name id) {
     case Builtins::kArrayPrototypeKeys:
     case Builtins::kArrayPrototypeLastIndexOf:
     case Builtins::kArrayPrototypeSlice:
+    case Builtins::kArraySlice:
     case Builtins::kArrayPrototypeSort:
     case Builtins::kArrayPrototypeToLocaleString:
     case Builtins::kArrayPrototypeToString:

src/torque/declaration-visitor.cc

@@ -228,8 +228,25 @@ void DeclarationVisitor::Visit(SpecializationDeclaration* decl) {
 
   if (matching_callable == nullptr) {
     std::stringstream stream;
+    if (generic_list->list().size() == 0) {
+      stream << "no generic defined with the name " << decl->name;
+      ReportError(stream.str());
+    }
     stream << "specialization of " << decl->name
-           << " doesn't match any generic declaration";
+           << " doesn't match any generic declaration\n";
+    stream << "specialization signature:";
+    stream << "\n  " << signature_with_types;
+    stream << "\ncandidates are:";
+    for (Generic* generic : generic_list->list()) {
+      SpecializationKey key = {generic,
+                               GetTypeVector(decl->generic_parameters)};
+      Declarations::CleanNodeScopeActivator specialization_activator(
+          declarations(), decl);
+      DeclareSpecializedTypes(key);
+      Signature generic_signature_with_types =
+          MakeSignature(generic->declaration()->callable->signature.get());
+      stream << "\n  " << generic_signature_with_types;
+    }
     ReportError(stream.str());
   }
 

test/mjsunit/array-natives-elements.js

@@ -112,15 +112,19 @@ function array_natives_test() {
   assertEquals([2], a2.slice(1,2));
   a2 = [1.1,2,3];
   assertTrue(%HasDoubleElements(a2.slice()));
-  assertTrue(%HasDoubleElements(a2.slice(1)));
-  assertTrue(%HasDoubleElements(a2.slice(1, 2)));
+  assertTrue(%HasDoubleElements(a2.slice(1)) ||
+             %HasSmiElements(a2.slice(1)));
+  assertTrue(%HasDoubleElements(a2.slice(1, 2)) ||
+            %HasSmiElements(a2.slice(1, 2)));
   assertEquals([1.1,2,3], a2.slice());
   assertEquals([2,3], a2.slice(1));
   assertEquals([2], a2.slice(1,2));
   a2 = [{},2,3];
   assertTrue(%HasObjectElements(a2.slice()));
-  assertTrue(%HasObjectElements(a2.slice(1)));
-  assertTrue(%HasObjectElements(a2.slice(1, 2)));
+  assertTrue(%HasObjectElements(a2.slice(1)) ||
+             %HasSmiElements(a2.slice(1)));
+  assertTrue(%HasObjectElements(a2.slice(1, 2)) ||
+             %HasSmiElements(a2.slice(1, 2)));
   assertEquals([{},2,3], a2.slice());
   assertEquals([2,3], a2.slice(1));
   assertEquals([2], a2.slice(1,2));

test/mjsunit/regress/regress-778668.js

@@ -2,6 +2,22 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+(function () {
+  function f() {
+    arguments.length = -5;
+    Array.prototype.slice.call(arguments);
+  }
+  f('a')
+})();
+
+(function () {
+  function f() {
+    arguments.length = 2.3;
+    Array.prototype.slice.call(arguments);
+  }
+  f('a')
+})();
+
 (function () {
   function f( __v_59960) {
     arguments.length = -5;
@@ -13,7 +29,6 @@
 (function () {
   function f( __v_59960) {
     arguments.length = 2.3;
-    print(arguments.length);
     Array.prototype.slice.call(arguments);
   }
   f('a')

third_party/v8/builtins/array-sort.tq

@@ -325,14 +325,12 @@ module array {
   builtin CanUseSameAccessor<ElementsAccessor: type>(
       context: Context, receiver: JSReceiver, initialReceiverMap: Object,
       initialReceiverLength: Number): Boolean {
-    assert(IsJSArray(receiver));
-
-    let a: JSArray = UnsafeCast<JSArray>(receiver);
+    const a: JSArray = Cast<JSArray>(receiver) otherwise unreachable;
     if (a.map != initialReceiverMap) return False;
 
     assert(TaggedIsSmi(initialReceiverLength));
     let originalLength: Smi = UnsafeCast<Smi>(initialReceiverLength);
-    if (a.length_fast != originalLength) return False;
+    if (a.length != originalLength) return False;
 
     return True;
   }
@@ -547,13 +545,7 @@ module array {
   // Used for OOB asserts in Copy* builtins.
   macro GetReceiverLengthProperty(
       implicit context: Context)(sortState: FixedArray): Smi {
-    const receiver: JSReceiver = GetReceiver(sortState);
-
-    if (IsJSArray(receiver)) return UnsafeCast<JSArray>(receiver).length_fast;
-
-    const len: Number =
-        ToLength_Inline(context, GetProperty(receiver, kLengthString));
-    return UnsafeCast<Smi>(len);
+    return Cast<Smi>(GetLengthProperty(GetReceiver(sortState))) otherwise unreachable;
   }
 
   macro CopyToTempArray(
@@ -1747,12 +1739,10 @@ module array {
     sortState[kBailoutStatusIdx] = kSuccess;
 
     try {
-      const a: JSArray = Cast<JSArray>(obj) otherwise Slow;
-      const elementsKind: ElementsKind = map.elements_kind;
-      if (!IsFastElementsKind(elementsKind)) goto Slow;
+      const a: FastJSArray = Cast<FastJSArray>(receiver) otherwise Slow;
 
       // 3. Let len be ? ToLength(? Get(obj, "length")).
-      const len: Smi = a.length_fast;
+      const len: Smi = a.length;
       if (len < 2) return receiver;
 
       // TODO(szuend): Investigate performance tradeoff of skipping this step
@@ -1762,6 +1752,7 @@ module array {
 
       sortState[kInitialReceiverLengthIdx] = len;
 
+      const elementsKind: ElementsKind = map.elements_kind;
       if (IsDoubleElementsKind(elementsKind)) {
         InitializeSortStateAccessor<FastDoubleElements>(sortState);
       } else if (elementsKind == PACKED_SMI_ELEMENTS) {

tools/torque/format-torque.py

@@ -45,13 +45,13 @@ def postprocess(output):
   output = re.sub(r',([\n ]*)\/\*_LABELS_HOLD_\*\/', r'\1labels', output)
   output = re.sub(r'\/\*_OPE \'([^\']+)\'\*\/', r"operator '\1'", output)
   output = re.sub(r'\/\*_TYPE\*\/(\s*)switch', r'typeswitch', output)
-  output = re.sub(r'case ([^\:]+)\:\s*\/\*_TSXDEFERRED_\*\/',
+  output = re.sub(r'case (\w+)\:\s*\/\*_TSXDEFERRED_\*\/',
       r'case (\1): deferred', output)
-  output = re.sub(r'case ([^\:]+)\:\s*\/\*_TSX\*\/',
+  output = re.sub(r'case (\w+)\:\s*\/\*_TSX\*\/',
       r'case (\1):', output)
-  output = re.sub(r'case ([^\:]+)\:\s*\/\*_TSVDEFERRED_([^\:]+)\:\*\/',
+  output = re.sub(r'case (\w+)\:\s*\/\*_TSVDEFERRED_([^\:]+)\:\*\/',
       r'case (\2: \1): deferred', output)
-  output = re.sub(r'case ([^\:]+)\:\s*\/\*_TSV([^\:]+)\:\*\/',
+  output = re.sub(r'case (\w+)\:\s*\/\*_TSV([^\:]+)\:\*\/',
       r'case (\2: \1):', output)
   output = re.sub(r'\n_GeNeRaTeS00_\s*\/\*([^@]+)@\*\/',
       r"\n    generates '\1'", output)