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Language mapping for JavaScript

SIMD.js defines primitive SIMD types with a [[SIMDElements]] field containing one of the types from the portable SIMD specification. The corresponding SIMD type descriptors have an [[Interpretation]] field referencing one of the SIMD interpretations in this spec.

Constructor [[SIMDElements]] type [[Interpretation]]
SIMD.Float32x4 v128 f32x4
SIMD.Int32x4 v128 s32x4
SIMD.Int16x8 v128 s16x8
SIMD.Int8x16 v128 s8x16
SIMD.Uint32x4 v128 u32x4
SIMD.Uint16x8 v128 u16x8
SIMD.Uint8x16 v128 u8x16
SIMD.Bool32x4 b32x4 b32x4
SIMD.Bool16x8 b16x4 b16x8
SIMD.Bool8x16 b8x16 b8x16

SIMD.js does not currently provide mappings for any of the 64x2 types.

Abstract operations

SIMDCreate(descriptor, elements)

  1. Return the SIMD value specified by the record { [[SIMDTypeDescriptor]]: descriptor, [[SIMDElements]]: elements }.

SIMDUnaryOp(a, op, descriptor)

  1. If a.[[SIMDTypeDescriptor]] is not descriptor, throw a TypeError exception.
  2. Let res be descriptor.[[Interpretation]].op(a.[[SIMDElements]]).
  3. Return SIMDCreate(descriptor, res).

SIMDBinaryOp(a, b, op, descriptor, outputDescriptor)

  1. If a.[[SIMDTypeDescriptor]] is not descriptor or b.[[SIMDTypeDescriptor]] is not descriptor, throw a TypeError exception.
  2. If outputDescriptor is not provided, let outputDescriptor be descriptor.
  3. Let res be descriptor.[[Interpretation]].op(a.[[SIMDElements]], b.[[SIMDElements]]).
  4. Return SIMDCreate(outputDescriptor, res).

SIMDRelationalOp(a, b, op, descriptor)

  1. Let outputDescriptor be SIMDBoolType(descriptor).
  2. Return SIMDBinaryOp(a, b, op, descriptor, outputDescriptor).

SIMDScalarOp(a, bits, op, descriptor)

  1. If a.[[SIMDTypeDescriptor]] is not descriptor, throw a TypeError exception.
  2. Let scalar be ToUint8(bits).
  3. Let res be descriptor.[[Interpretation]].op(a.[[SIMDElements]], scalar).
  4. Return SIMDCreate(descriptor, res).

Properties of the SIMDConstructor constructors

Unary operations

The unary operations listed in the table below are defined as properties «SIMD»Constructor.«Operation»(a) where «SIMD» is one of the SIMD types and «Operation» is the name of the operation.

  1. Let result be SIMDUnaryOp(a, «Operation», «SIMD»Descriptor).
  2. ReturnIfAbrupt(result).
  3. Return result.
«Operation» SIMD types supported
neg integer and floating-point
sqrt floating-point
reciprocalSqrtApproximation floating-point
reciprocalApproximation floating-point
abs floating-point
not integer and boolean

Binary operations

The unary operations listed in the table below are defined as properties «SIMD»Constructor.«Operation»(a, b) where «SIMD» is one of the SIMD types and «Operation» is the name of the operation.

  1. Let result be SIMDBinaryOp(a, b, «Operation», «SIMD»Descriptor).
  2. ReturnIfAbrupt(result).
  3. Return result.
«Operation» SIMD types supported
add integer and floating-point
sub integer and floating-point
mul integer and floating-point
div floating-point
max floating-point
min floating-point
maxNum floating-point
minNum floating-point
and integer and boolean
xor integer and boolean
or integer and boolean
addSaturate 8x16 and 16x8 integers
subSaturate 8x16 and 16x8 integers

Relational operations

The relational operations listed in the table below are defined as properties «SIMD»Constructor.«Operation»(a, b) where «SIMD» is one of the SIMD types and «Operation» is the name of the operation.

  1. Let result be SIMDRelationalOp(a, b, «Operation», «SIMD»Descriptor).
  2. ReturnIfAbrupt(result).
  3. Return result.
«Operation» SIMD types supported
lessThan integer and floating-point
lessThanOrEqual integer and floating-point
greaterThan integer and floating-point
greaterThanOrEqual integer and floating-point
equal integer and floating-point
notEqual integer and floating-point

«SIMD»Constructor.from«TIMD»Bits(a)

In this definition, «TIMD» is not «SIMD», and both «TIMD» and «SIMD» range over all integer and floating-point SIMD types. These types all have a v128 [[SIMDElements]] field which is simply reinterpreted as the new type.

  1. If a.[[SIMDTypeDescriptor]] is not «TIMD»Descriptor, throw a TypeError exception.
  2. Let res be a.[[SIMDElements]].
  3. Return SIMDCreate(«SIMD»Descriptor, res).

«SIMD»Constructor.from«TIMD»(a)

Conversion between floating-point and integer lanes is provided for the 32x4 integer types:

«SIMD» «TIMD» «Operation» Fallible
Float32x4 Int32x4 f32x4.fromSignedInt No
Float32x4 Uint32x4 f32x4.fromUnsignedInt No
Int32x4 Float32x4 s32x4.fromFloat Yes
Uint32x4 Float32x4 u32x4.fromFloat Yes

The integer-to-float conversions always succeed, but the float-to-integer conversions can fail:

  1. If a.[[SIMDTypeDescriptor]] is not «TIMD»Descriptor, throw a TypeError exception.
  2. If conversion is fallible:
    1. Let (res, fail) be «Operation»(a.[[SIMDElements]]).
  3. Otherwise:
    1. Let res be «Operation»(a.[[SIMDElements]]).
    2. Let fail be false.
  4. If fail is true, throw a RangeError exception.
  5. Return SIMDCreate(«SIMD»Descriptor, res).

«SIMD»Constructor.anyTrue(a)

This operation is only defined on boolean SIMD types.

  1. If a.[[SIMDTypeDescriptor]] is not «SIMD»Descriptor, throw a TypeError exception.
  2. Return «SIMD»Descriptor.[[Interpretation]].anyTrue(a.[[SIMDElements]]).

«SIMD»Constructor.shiftLeftByScalar(a, bits)

This operation is only defined on integer SIMD types.

  1. Let result be SIMDScalarOp(a, bits, shiftLeftByScalar, «SIMD»Descriptor).
  2. ReturnIfAbrupt(result).
  3. Return result.

«SIMD»Constructor.shuffle(a, b, ...lanes)

This operation exists only on integer and floating point SIMD types.

  1. If a.[[SIMDTypeDescriptor]] is not «SIMD»Descriptor, or if b.[[SIMDTypeDescriptor]] is not «SIMD»Descriptor, throw a TypeError exception.
  2. Let indices be a new List.
    1. For integer n from 0 to «SIMD»Descriptor.[[VectorLength]],
      1. Let lane be lanes[i], or 0 if lanes is not long enough.
      2. Let index be SIMDToLane(«SIMD»Descriptor.[[VectorLength]] * 2, lane).
      3. ReturnIfAbrupt(index).
      4. Append index to the end of indices.
  3. Let res be «SIMD»Descriptor.[[Interpretation]].shuffle(a, b, indices).
  4. Return SIMDCreate(«SIMD»Descriptor, res).