Globals

The following global constants and functions are present alongside the standard library's classes.

Constants

• const NaN: auto // f32 or f64
  

  Not a number as a 32-bit or 64-bit float depending on context. Compiles to a constant.

• const Infinity: auto // f32 or f64
  

  Positive infinity as a 32-bit or 64-bit float depending on context. Compiles to a constant.

Functions

• function isNaN<T>(value: T): bool
  

  Tests if a 32-bit or 64-bit float is NaN.

• function isFinite<T>(value: T): bool
  

  Tests if a 32-bit or 64-bit float is finite, that is not NaN or +/-Infinity.

• function parseInt(str: string, radix?: i32): f64
  

  Parses a string representing an integer to an f64 number Returns NaN on invalid inputs.

  Type-specific variants of parseInt are available separately:

  • F32.parseInt to parse to a 32-bit float.
  • I8.parseInt to parse to a signed 8-bit integer, respectively U8.parseInt if unsigned.
  • I16.parseInt to parse to a signed 16-bit integer, respectively U16.parseInt if unsigned.
  • I32.parseInt to parse to a signed 32-bit integer, respectively U32.parseInt if unsigned.
  • I64.parseInt to parse to a signed 64-bit integer, respectively U64.parseInt if unsigned.

• function parseFloat(str: string): f64
  

  Parses a string to a 64-bit float. Returns NaN on invalid inputs.

Builtins

The following builtins provide direct access to WebAssembly and compiler features. They form the low-level foundation of the standard library, while also being available for everyone to utilize where directly tapping into WebAssembly or the compiler is desired.

Static type checks

By making use of the following special type checks, especially in generic contexts, untaken branches can be eliminated statically, leading to concrete WebAssembly functions that handle one type specificially.

• function isInteger<T>(value?: T): bool
  

  Tests if the specified type or expression is of an integer type and not a reference. Compiles to a constant.

• function isSigned<T>(value?: T): bool
  

  Tests if the specified type or expression can represent negative numbers. Compiles to a constant.

• function isFloat<T>(value?: T): bool
  

  Tests if the specified type or expression is of a float type. Compiles to a constant.

• function isVector<T>(value?: T): bool
  

  Tests if the specified type or expression is of a SIMD vector type. Compiles to a constant.

• function isReference<T>(value?: T): bool
  

  Tests if the specified type or expression is of a reference type. Compiles to a constant.

• function isString<T>(value?: T): bool
  

  Tests if the specified type or expression can be used as a string. Compiles to a constant.

• function isArray<T>(value?: T): bool
  

  Tests if the specified type or expression can be used as an array. Compiles to a constant.

• function isFunction<T>(value?: T): bool
  

  Tests if the specified type or expression is of a function type. Compiles to a constant.

• function isNullable<T>(value?: T): bool
  

  Tests if the specified type or expression is of a nullable reference type. Compiles to a constant.

• function isDefined(expression: auto): bool
  

  Tests if the specified expression resolves to a defined element. Compiles to a constant.

• function isConstant(expression: auto): bool
  

  Tests if the specified expression evaluates to a constant value. Compiles to a constant.

• function isManaged<T>(expression: auto): bool
  

  Tests if the specified type or expression is of a managed type. Compiles to a constant. Usually only relevant when implementing custom collection-like classes.

Example of static type checking

function add<T>(a: T, b: T): T {
  return a + b // addition if numeric, string concatenation if a string
}

function add<T>(a: T, b: T): T {
  if (isString<T>()) { // eliminated if T is not a string
    return parseInt(a) + parseInt(b)
  } else { // eliminated if T is a string
    return a + b
  }
}

TIP

If you are not going to use low-level WebAssembly in the foreseeable future, feel free to come back to the following paragraphs at a later time.

Utilities

• function bswap<T>(value: T): T
  

  Reverses the byte order of the specified integer.

• function sizeof<T>(): usize
  

  Determines the byte size of the respective basic type. Means: If T is a class type, the size of usize, the pointer type, is returned. To obtain the size of a class in memory, use offsetof<T>() instead. Compiles to a constant.

• function offsetof<T>(fieldName?: string): usize
  

  Determines the offset of the specified field within the given class type. If fieldName is omitted, this returns what could be interpreted as either the size of the class, or the offset where the next field would be located, before alignment. Compiles to a constant. The fieldName argument must be a compile-time constant string because there is no information about field names anymore at runtime. Therefore, the field's name must be known at the time the returned constant is computed.

• function alignof<T>(): usize
  

  Determines the alignment (log2) of the specified underlying basic type; i.e. If T is a class type, the alignment of usize is returned. Compiles to a constant.

• function assert<T>(isTrueish: T, message?: string): T
  

  Traps if the specified value is not true-ish, otherwise returns the non-nullable value. Like assertions in C, aborting the entire program if the expectation fails. Where desired, the --noAssert compiler option can be used to disable assertions in production.

• function trace(message: string, n?: i32, a0?: f64, a1?: f64, a2?: f64, a3?: f64, a4?: f64): void
  

  Simple trace function which prints message and 5 optional f64 arguments to a console. n is count of used arguments.

  Usage examples

  trace("foo");
  trace("one arg:", 1, 5.0);
  trace("three args:", 3, 1.0, <f64>2, 3);
  

• function instantiate<T>(...args: auto[]): T
  

  Instantiates a new instance of T using the specified constructor arguments.

• function changetype<T>(value: auto): T
  

  Changes the type of a value to another one. Useful for casting class instances to their pointer values and vice-versa.

• function idof<T>(): u32
  

  Obtains the computed unique id of a class type. Usually only relevant when allocating objects or dealing with RTTI externally.

• function nameof<T>(value?: T): string
  

  Returns the name of a given type.

WebAssembly

Math

The following generic built-ins compile to WebAssembly instructions directly.

• function clz<T>(value: T): T
  

  Performs the sign-agnostic count leading zero bits operation on a 32-bit or 64-bit integer. All zero bits are considered leading if the value is zero.

  T	Instruction
  i8, u8, i16, u16, i32, u32, bool	i32.clz
  i64, u64	i64.clz

• function ctz<T>(value: T): T
  

  Performs the sign-agnostic count trailing zero bits operation on a 32-bit or 64-bit integer. All zero bits are considered trailing if the value is zero.

  T	Instruction
  i8, u8, i16, u16, i32, u32, bool	i32.ctz
  i64, u64	i64.ctz

• function popcnt<T>(value: T): T
  

  Performs the sign-agnostic count number of one bits operation on a 32-bit or 64-bit integer.

  T	Instruction
  i8, u8, i16, u16, i32, u32	i32.popcnt
  i64, u64	i64.popcnt
  bool	none

• function rotl<T>(value: T, shift: T): T
  

  Performs the sign-agnostic rotate left operation on a 32-bit or 64-bit integer.

  T	Instruction
  i32, u32	i32.rotl
  i64, u64	i64.rotl
  i8, u8, i16, u16	emulated
  bool	none

• function rotr<T>(value: T, shift: T): T
  

  Performs the sign-agnostic rotate right operation on a 32-bit or 64-bit integer.

  T	Instruction
  i32, u32	i32.rotr
  i64, u64	i64.rotr
  i8, u8, i16, u16	emulated
  bool	none

• function abs<T>(value: T): T
  

  Computes the absolute value of an integer or float.

  T	Instruction
  f32	f32.abs
  f64	f64.abs
  i8, i16, i32, i64	emulated
  u8, u16, u32, u64, bool	none

• function max<T>(left: T, right: T): T
  

  Determines the maximum of two integers or floats. If either operand is NaN, returns NaN.

  T	Instruction
  f32	f32.max
  f64	f64.max
  i8, u8, i16, u16, i32, u32, i64, u64, bool	emulated

• function min<T>(left: T, right: T): T
  

  Determines the minimum of two integers or floats. If either operand is NaN, returns NaN.

  T	Instruction
  f32	f32.min
  f64	f64.min
  i8, u8, i16, u16, i32, u32, i64, u64, bool	emulated

• function ceil<T>(value: T): T
  

  Performs the ceiling operation on a 32-bit or 64-bit float.

  T	Instruction
  f32	f32.ceil
  f64	f64.ceil
  i8, u8, i16, u16, i32, u32, i64, u64, bool	none

• function floor<T>(value: T): T
  

  Performs the floor operation on a 32-bit or 64-bit float.

  T	Instruction
  f32	f32.floor
  f64	f64.floor
  i8, u8, i16, u16, i32, u32, i64, u64, bool	none

• function copysign<T>(x: T , y: T): T
  

  Composes a 32-bit or 64-bit float from the magnitude of x and the sign of y.

  T	Instruction
  f32	f32.copysign
  f64	f64.copysign

• function nearest<T>(value: T): T
  

  Rounds to the nearest integer half to even of a 32-bit or 64-bit float.

  T	Instruction
  f32	f32.nearest
  f64	f64.nearest
  i8, u8, i16, u16, i32, u32, i64, u64, bool	none

• function reinterpret<TTo>(value: auto): TTo
  

  Reinterprets the bits of the specified value as type T.

  TTo	Instruction
  i32, u32	i32.reinterpret_f32
  i64, u64	i64.reinterpret_f64
  f32	f32.reinterpret_i32
  f64	f64.reinterpret_i64

• function sqrt<T>(value: T): T
  

  Calculates the square root of a 32-bit or 64-bit float.

  T	Instruction
  f32	f32.sqrt
  f64	f64.sqrt

• function trunc<T>(value: T): T
  

  Rounds to the nearest integer towards zero of a 32-bit or 64-bit float.

  T	Instruction
  f32	f32.trunc
  f64	f64.trunc
  i8, u8, i16, u16, i32, u32, i64, u64, bool	none

Memory

Similarly, the following built-ins emit WebAssembly instructions accessing or otherwise modifying memory.

NOTE

The immOffset and immAlign arguments, if provided, must be compile time constant values. See more details in rationale (opens new window).

• function load<T>(ptr: usize, immOffset?: usize, immAlign?: usize): T
  

  Loads a value of the specified type from memory. Equivalent to dereferencing a pointer in other languages.

  T	Instruction	If contextual type is i64
  i8	i32.load8_s	i64.load8_s
  u8	i32.load8_u	i64.load8_u
  i16	i32.load16_s	i64.load16_s
  u16	i32.load16_u	i64.load16_u
  i32	i32.load	i64.load32_s
  u32	i32.load	i64.load32_u
  i64, u64	i64.load	n/a
  f32	f32.load	n/a
  f64	f64.load	n/a
  <ref>	i32/i64.load	n/a

• function store<T>(ptr: usize, value: auto, immOffset?: usize, immAlign?: usize): void
  

  Stores a value of the specified type to memory. Equivalent to dereferencing a pointer in other languages and assigning a value.

  T	Instruction	If value is i64
  i8, u8	i32.store8	i64.store8
  i16, u16	i32.store16	i64.store16
  i32, u32	i32.store	i64.store32
  i64, u64	i64.store	n/a
  f32	f32.store	n/a
  f64	f64.store	n/a
  <ref>	i32/i64.store	n/a

• function memory.size(): i32
  

  Returns the current size of the memory in units of pages. One page is 64kb.

• function memory.grow(value: i32): i32
  

  Grows linear memory by a given unsigned delta of pages. One page is 64kb. Returns the previous size of the memory in units of pages or -1 on failure.

  WARNING

  Calling memory.grow where a memory manager is present might break it.

• function memory.copy(dst: usize, src: usize, n: usize): void
  

  Copies n bytes from src to dst . Regions may overlap. Emits the respective instruction if bulk-memory is enabled, otherwise ships a polyfill.

• function memory.fill(dst: usize, value: u8, n: usize): void
  

  Fills n bytes at dst with the given byte value. Emits the respective instruction if bulk-memory is enabled, otherwise ships a polyfill.

• function memory.repeat(dst: usize, src: usize, srcLength: usize, count: usize): void
  

  Repeats a sequence of bytes given as src with srcLength count times into destination dst.

• function memory.compare(lhs: usize, rhs: usize, n: usize): i32
  

  Compares the first n bytes of left and right and returns a value that indicates their relationship:

  • Negative value if the first differing byte in lhs is less than the corresponding byte in rhs.
  • Positive value if the first differing byte in lhs is greater than the corresponding byte in rhs.
  • Zero​ if all n bytes of lhs and rhs are equal.

• function memory.data(size: i32, align?: i32): usize
  

  Gets a pointer to a zeroed static chunk of memory of the given size. Alignment defaults to 16. Arguments must be compile-time constants.

• function memory.data<T>(values: T[], align?: i32): usize
  

  Gets a pointer to a pre-initialized static chunk of memory. Alignment defaults to the size of T. Arguments must be compile-time constants.

Control flow

• function select<T>(ifTrue: T, ifFalse: T, condition: bool): T
  

  Selects one of two pre-evaluated values depending on the condition. Differs from an if/else in that both arms are always executed and the final value is picked based on the condition afterwards. Performs better than an if/else only if the condition is random (means: branch prediction is not going to perform well) and both alternatives are cheap. It is also worth to note that Binaryen will do relevant optimizations like switching to a select automatically, so simply using a ternary ? : may be preferable.

• function unreachable(): auto
  

  Emits an unreachable instruction that results in a runtime error (trap) when executed. Both a statement and an expression of any type. Beware that trapping in managed code will most likely lead to memory leaks or even break the program because it ends execution prematurely.

Atomics 🦄

The following instructions represent the WebAssembly threads and atomics (opens new window) specification. Must be enabled with --enable threads.

• function atomic.load<T>(ptr: usize, immOffset?: usize): T
  

  Atomically loads an integer value from memory and returns it.

• function atomic.store<T>(ptr: usize, value: auto, immOffset?: usize): void
  

  Atomically stores an integer value to memory.

• function atomic.add<T>(ptr: usize, value: T, immOffset?: usize): T
  

  Atomically adds an integer value in memory.

• function atomic.sub<T>(ptr: usize, value: T, immOffset?: usize): T
  

  Atomically subtracts an integer value in memory.

• function atomic.and<T>(ptr: usize, value: T, immOffset?: usize): T
  

  Atomically performs a bitwise AND operation on an integer value in memory.

• function atomic.or<T>(ptr: usize, value: T, immOffset?: usize): T
  

  Atomically performs a bitwise OR operation on an integer value in memory.

• function atomic.xor<T>(ptr: usize, value: T, immOffset?: usize): T
  

  Atomically performs a bitwise XOR operation on an integer value in memory.

• function atomic.xchg<T>(ptr: usize, value: T, immOffset?: usize): T
  

  Atomically exchanges an integer value in memory.

• function atomic.cmpxchg<T>(ptr: usize, expected: T, replacement: T, immOffset?: usize): T
  

  Atomically compares and exchanges an integer value in memory if the condition is met.

• function atomic.wait<T>(ptr: usize, expected: T, timeout: i64): AtomicWaitResult
  

  Performs a wait operation on an address in memory, suspending this agent if the integer condition is met. Return values are

  Value	Description
  0	OK - Woken by another agent.
  1	NOT_EQUAL - Loaded value did not match the expected value.
  2	TIMED_OUT - Not woken before the timeout expired.

• function atomic.notify(ptr: usize, count: i32): i32
  

  Performs a notify operation on an address in memory waking up suspended agents.

• function atomic.fence(): void
  

  Performs a fence operation, preserving synchronization guarantees of higher level languages.

SIMD 🦄

Likewise, these represent the WebAssembly SIMD (opens new window) specification. Must be enabled with --enable simd.

• function v128(a: i8, ... , p: i8): v128
  

  Initializes a 128-bit vector from sixteen 8-bit integer values. Arguments must be compile-time constants.

  See Constructing constant vectors for additional type-specific options.

• function v128.splat<T>(x: T): v128
  

  Creates a vector with identical lanes.

  T	Instruction
  i8, u8	i8x16.splat
  i16, u16	i16x8.splat
  i32, u32	i32x4.splat
  i64, u64	i64x2.splat
  f32	f32x4.splat
  f64	f64x2.splat

• function v128.extract_lane<T>(x: v128, idx: u8): T
  

  Extracts one lane as a scalar.

  T	Instruction
  i8	i8x16.extract_lane_s
  u8	i8x16.extract_lane_u
  i16	i16x8.extract_lane_s
  u16	i16x8.extract_lane_u
  i32, u32	i32x4.extract_lane
  i64, u64	i64x2.extract_lane
  f32	f32x4.extract_lane
  f64	f64x2.extract_lane

• function v128.replace_lane<T>(x: v128, idx: u8, value: T): v128
  

  Replaces one lane.

  T	Instruction
  i8, u8	i8x16.replace_lane
  i16, u16	i16x8.replace_lane
  i32, u32	i32x4.replace_lane
  i64, u64	i64x2.replace_lane
  f32	f32x4.replace_lane
  f64	f64x2.replace_lane

• function v128.shuffle<T>(a: v128, b: v128, ...lanes: u8[]): v128
  

  Selects lanes from either vector according to the specified lane indexes.

  T	Instruction
  i8, u8	i8x16.shuffle
  i16, u16	i8x16.shuffle emulating i16x8.shuffle
  i32, u32	i8x16.shuffle emulating i32x4.shuffle
  i64, u64	i8x16.shuffle emulating i64x2.shuffle
  f32	i8x16.shuffle emulating f32x4.shuffle
  f64	i8x16.shuffle emulating f64x2.shuffle

• function v128.swizzle(a: v128, s: v128): v128
  

  Selects 8-bit lanes from the first vector according to the indexes [0-15] specified by the 8-bit lanes of the second vector.

• function v128.load(ptr: usize, immOffset?: usize, immAlign?: usize): v128
  

  Loads a vector from memory.

• function v128.load_ext<TFrom>(ptr: usize, immOffset?: usize, immAlign?: usize): v128
  

  Creates a vector by loading the lanes of the specified integer type and extending each to the next larger type.

  TFrom	Instruction
  i8	v128.load8x8_s
  u8	v128.load8x8_u
  i16	v128.load16x4_s
  u16	v128.load16x4_u
  i32	v128.load32x2_s
  u32	v128.load32x2_u

• function v128.load_zero<TFrom>(ptr: usize, immOffset?: usize, immAlign?: usize): v128
  

  Creates a vector by loading a value of the specified type into the lowest bits and initializing all other bits of the vector to zero.

  TFrom	Instruction
  i32, u32, f32	v128.load32_zero
  i64, u64, f64	v128.load64_zero

• function v128.load_lane<T>(
    ptr: usize, vec: v128, idx: u8, immOffset?: usize, immAlign?: usize
  ): v128
  

  Loads a single lane from memory into the specified lane of the given vector. Other lanes are bypassed as is.

  T	Instruction
  i8, u8	v128.load8_lane
  i16, u16	v128.load16_lane
  i32, u32, f32	v128.load32_lane
  i64, u64, f64	v128.load64_lane

• function v128.store_lane<T>(
    ptr: usize, vec: v128, idx: u8, immOffset?: usize, immAlign?: usize
  ): v128
  

  Stores the single lane at the specified index of the given vector to memory.

  T	Instruction
  i8, u8	v128.store8_lane
  i16, u16	v128.store16_lane
  i32, u32, f32	v128.store32_lane
  i64, u64, f64	v128.store64_lane

• function v128.load_splat<T>(ptr: usize, immOffset?: usize, immAlign?: usize): v128
  

  Creates a vector with identical lanes by loading the splatted value.

  T	Instruction
  i8, u8	v128.load8_splat
  i16, u16	v128.load16_splat
  i32, u32, f32	v128.load32_splat
  i64, u64, f64	v128.load64_splat

• function v128.store(ptr: usize, value: v128, immOffset?: usize, immAlign?: usize): void
  

  Stores a vector to memory.

• function v128.add<T>(a: v128, b: v128): v128
  

  Adds each lane.

  T	Instruction
  i8, u8	i8x16.add
  i16, u16	i16x8.add
  i32, u32	i32x4.add
  i64, u64	i64x2.add
  f32	f32x4.add
  f64	f64x2.add

• function v128.sub<T>(a: v128, b: v128): v128
  

  Subtracts each lane.

  T	Instruction
  i8, u8	i8x16.sub
  i16, u16	i16x8.sub
  i32, u32	i32x4.sub
  i64, u64	i64x2.sub
  f32	f32x4.sub
  f64	f64x2.sub

• function v128.mul<T>(a: v128, b: v128): v128
  

  Multiplies each lane.

  T	Instruction
  i16, u16	i16x8.mul
  i32, u32	i32x4.mul
  i64, u64	i64x2.mul
  f32	f32x4.mul
  f64	f64x2.mul

• function v128.div<T>(a: v128, b: v128): v128
  

  Divides each floating point lane.

  T	Instruction
  f32	f32x4.div
  f64	f64x2.div

• function v128.neg<T>(a: v128): v128
  

  Negates each lane.

  T	Instruction
  i8, u8	i8x16.neg
  i16, u16	i16x8.neg
  i32, u32	i32x4.neg
  i64, u64	i64x2.neg
  f32	f32x4.neg
  f64	f64x2.neg

• function v128.add_sat<T>(a: v128, b: v128): v128
  

  Adds each signed small integer lane using saturation.

  T	Instruction
  i8	i8x16.add_sat_s
  u8	i8x16.add_sat_u
  i16	i16x8.add_sat_s
  u16	i16x8.add_sat_u

• function v128.sub_sat<T>(a: v128, b: v128): v128
  

  Subtracts each signed small integer lane using saturation.

  T	Instruction
  i8	i8x16.sub_sat_s
  u8	i8x16.sub_sat_u
  i16	i16x8.sub_sat_s
  u16	i16x8.sub_sat_u

• function v128.shl<T>(a: v128, b: i32): v128
  

  Performs a bitwise left shift by a scalar on each integer lane.

  T	Instruction
  i8, u8	i8x16.shl
  i16, u16	i16x8.shl
  i32, u32	i32x4.shl
  i64, u64	i64x2.shl

• function v128.shr<T>(a: v128, b: i32): v128
  

  Performs a bitwise right shift by a scalar on each integer lane.

  T	Instruction
  i8	i8x16.shr_s
  u8	i8x16.shr_u
  i16	i16x8.shr_s
  u16	i16x8.shr_u
  i32	i32x4.shr_s
  u32	i32x4.shr_u
  i64	i64x2.shr_s
  u64	i64x2.shr_u

• function v128.and(a: v128, b: v128): v128
  

  Performs the bitwise a & b operation on each lane.

• function v128.or(a: v128, b: v128): v128
  

  Performs the bitwise a | b operation on each lane.

• function v128.xor(a: v128, b: v128): v128
  

  Performs the bitwise a ^ b operation on each lane.

• function v128.andnot(a: v128, b: v128): v128
  

  Performs the bitwise !a & b operation on each lane.

• function v128.not(a: v128): v128
  

  Performs the bitwise !a operation on each lane.

• function v128.bitselect(v1: v128, v2: v128, mask: v128): v128
  

  Selects bits of either vector according to the specified mask. Selects from v1 if the bit in mask is 1, otherwise from v2.

• function v128.any_true(a: v128): bool
  

  Reduces a vector to a scalar indicating whether any lane is considered true.

• function v128.all_true<T>(a: v128): bool
  

  Reduces a vector to a scalar indicating whether all lanes are considered true.

  T	Instruction
  i8, u8	i8x16.all_true
  i16, u16	i16x8.all_true
  i32, u32	i32x4.all_true
  i64, u64	i64x2.all_true

• function v128.bitmask<T>(a: v128): bool
  

  Extracts the high bit of each integer lane (except 64-bit) and produces a scalar mask with all bits concatenated.

  T	Instruction
  i8, u8	i8x16.bitmask
  i16, u16	i16x8.bitmask
  i32, u32	i32x4.bitmask
  i64, u64	i64x2.bitmask

• function v128.popcnt<T>(a: v128): v128
  

  Counts the number of bits set to one within each lane.

  T	Instruction
  i8, u8	i8x16.popcnt

• function v128.min<T>(a: v128, b: v128): v128
  

  Computes the minimum of each lane.

  T	Instruction
  i8	i8x16.min_s
  u8	i8x16.min_u
  i16	i16x8.min_s
  u16	i16x8.min_u
  i32	i32x4.min_s
  u32	i32x4.min_u
  f32	f32x4.min
  f64	f64x2.min

• function v128.max<T>(a: v128, b: v128): v128
  

  Computes the maximum of each lane.

  T	Instruction
  i8	i8x16.max_s
  u8	i8x16.max_u
  i16	i16x8.max_s
  u16	i16x8.max_u
  i32	i32x4.max_s
  u32	i32x4.max_u
  f32	f32x4.max
  f64	f64x2.max

• function v128.pmin<T>(a: v128, b: v128): v128
  

  Computes the psuedo-minimum of each lane.

  T	Instruction
  f32	f32x4.pmin
  f64	f64x2.pmin

• function v128.pmax<T>(a: v128, b: v128): v128
  

  Computes the pseudo-maximum of each lane.

  T	Instruction
  f32	f32x4.pmax
  f64	f64x2.pmax

• function v128.dot<T>(a: v128, b: v128): v128
  

  Computes the dot product of two 16-bit integer lanes each, yielding lanes one size wider than the input.

  T	Instruction
  i16	i32x4.dot_i16x8_s

• function v128.avgr<T>(a: v128, b: v128): v128)
  

  Computes the rounding average of each unsigned small integer lane.

  T	Instruction
  u8	i8x16.avgr_u
  u16	i16x8.avgr_u

• function v128.abs<T>(a: v128): v128
  

  Computes the absolute value of each lane (except 64-bit integers).

  T	Instruction
  i8, u8	i8x16.abs
  i16, u16	i16x8.abs
  i32, u32	i32x4.abs
  i64, u64	i64x2.abs
  f32	f32x4.abs
  f64	f64x2.abs

• function v128.sqrt<T>(a: v128): v128
  

  Computes the square root of each floating point lane.

  T	Instruction
  f32	f32x4.sqrt
  f64	f64x2.sqrt

• function v128.ceil<T>(a: v128): v128
  

  Performs the ceiling operation on each lane.

  T	Instruction
  f32	f32x4.ceil
  f64	f64x2.ceil

• function v128.floor<T>(a: v128): v128
  

  Performs the floor operation on each lane.

  T	Instruction
  f32	f32x4.floor
  f64	f64x2.floor

• function v128.trunc<T>(a: v128): v128
  

  Rounds to the nearest integer towards zero of each lane.

  T	Instruction
  f32	f32x4.trunc
  f64	f64x2.trunc

• function v128.nearest<T>(a: v128): v128
  

  Rounds to the nearest integer half to even of each lane.

  T	Instruction
  f32	f32x4.nearest
  f64	f64x2.nearest

• function v128.eq<T>(a: v128, b: v128): v128
  

  Computes which lanes are equal.

  T	Instruction
  i8, u8	i8x16.eq
  i16, u16	i16x8.eq
  i32, u32	i32x4.eq
  i64, u64	i64x2.eq
  f32	f32x4.eq
  f64	f64x2.eq

• function v128.ne<T>(a: v128, b: v128): v128
  

  Computes which lanes are not equal.

  T	Instruction
  i8, u8	i8x16.ne
  i16, u16	i16x8.ne
  i32, u32	i32x4.ne
  i64, u64	i64x2.ne
  f32	f32x4.ne
  f64	f64x2.ne

• function v128.lt<T>(a: v128, b: v128): v128
  

  Computes which lanes of the first vector are less than those of the second.

  T	Instruction
  i8	i8x16.lt_s
  u8	i8x16.lt_u
  i16	i16x8.lt_s
  u16	i16x8.lt_u
  i32	i32x4.lt_s
  u32	i32x4.lt_u
  i64	i64x2.lt_s
  f32	f32x4.lt
  f64	f64x2.lt

• function v128.le<T>(a: v128, b: v128): v128
  

  Computes which lanes of the first vector are less than or equal those of the second.

  T	Instruction
  i8	i8x16.le_s
  u8	i8x16.le_u
  i16	i16x8.le_s
  u16	i16x8.le_u
  i32	i32x4.le_s
  u32	i32x4.le_u
  i64	i64x2.le_s
  f32	f32x4.le
  f64	f64x2.le

• function v128.gt<T>(a: v128, b: v128): v128
  

  Computes which lanes of the first vector are greater than those of the second.

  T	Instruction
  i8	i8x16.gt_s
  u8	i8x16.gt_u
  i16	i16x8.gt_s
  u16	i16x8.gt_u
  i32	i32x4.gt_s
  u32	i32x4.gt_u
  i64	i64x2.gt_s
  f32	f32x4.gt
  f64	f64x2.gt

• function v128.ge<T>(a: v128, b: v128): v128
  

  Computes which lanes of the first vector are greater than or equal those of the second.

  T	Instruction
  i8	i8x16.ge_s
  u8	i8x16.ge_u
  i16	i16x8.ge_s
  u16	i16x8.ge_u
  i32	i32x4.ge_s
  u32	i32x4.ge_u
  i64	i64x2.ge_s
  f32	f32x4.ge
  f64	f64x2.ge

• function v128.convert<TFrom>(a: v128): v128
  

  Converts each lane of a vector from integer to single-precision floating point.

  TFrom	Instruction
  i32	f32x4.convert_i32x4_s
  u32	f32x4.convert_i32x4_u

• function v128.convert_low<TFrom>(a: v128): v128
  

  Converts the low lanes of a vector from integer to double-precision floating point.

  TFrom	Instruction
  i32	f64x2.convert_low_i32x4_s
  u32	f64x2.convert_low_i32x4_u

• function v128.trunc_sat<TTo>(a: v128): v128
  

  Truncates each lane of a vector from single-precision floating point to integer with saturation. Takes the target type.

  TTo	Instruction
  i32	i32x4.trunc_sat_f32x4_s
  u32	i32x4.trunc_sat_f32x4_u

• function v128.trunc_sat_zero<TTo>(a: v128): v128
  

  Truncates each lane of a vector from double-precision floating point to integer with saturation. Takes the target type.

  TTo	Instruction
  i32	i32x4.trunc_sat_f64x2_s_zero
  u32	i32x4.trunc_sat_f64x2_u_zero

• function v128.narrow<TFrom>(a: v128, b: v128): v128
  

  Narrows wider integer lanes to their respective narrower lanes.

  TFrom	Instruction
  i16	i8x16.narrow_i16x8_s
  u16	i8x16.narrow_i16x8_u
  i32	i16x8.narrow_i32x4_s
  u32	i16x8.narrow_i32x4_u

• function v128.extend_low<TFrom>(a: v128): v128
  

  Extends the low half of narrower integer lanes to their respective wider lanes.

  TFrom	Instruction
  i8	i16x8.extend_low_i8x16_s
  u8	i16x8.extend_low_i8x16_u
  i16	i32x4.extend_low_i16x8_s
  u16	i32x4.extend_low_i16x8_u
  i32	i64x2.extend_low_i32x4_s
  u32	i64x2.extend_low_i32x4_u

• function v128.extend_high<TFrom>(a: v128): v128
  

  Extends the high half of narrower integer lanes to their respective wider lanes.

  TFrom	Instruction
  i8	i16x8.extend_high_i8x16_s
  u8	i16x8.extend_high_i8x16_u
  i16	i32x4.extend_high_i16x8_s
  u16	i32x4.extend_high_i16x8_u
  i32	i64x2.extend_high_i32x4_s
  u32	i64x2.extend_high_i32x4_u

• function v128.extadd_pairwise<TFrom>(a: v128): v128
  

  Adds lanes pairwise producing twice wider extended results.

  TFrom	Instruction
  i16	i16x8.extadd_pairwise_i8x16_s
  u16	i16x8.extadd_pairwise_i8x16_u
  i32	i32x4.extadd_pairwise_i16x8_s
  u32	i32x4.extadd_pairwise_i16x8_u

• function v128.demote_zero<T>(a: v128): v128
  

  Demotes each float lane to lower precision. The higher lanes of the result are initialized to zero.

  T	Instruction
  f64	f32x4.demote_f64x2_zero

• function v128.promote_low<T>(a: v128): v128
  

  Promotes the lower float lanes to higher precision.

  T	Instruction
  f32	f64x2.promote_low_f32x4

• function v128.q15mulr_sat<T>(a: v128, b: v128): v128
  

  Performs the line-wise saturating rounding multiplication in Q15 format ((a[i] * b[i] + (1 << (Q - 1))) >> Q where Q=15).

  T	Instruction
  i16	i16x8.q15mulr_sat_s

• function v128.extmul_low<T>(a: v128, b: v128): v128
  

  Performs the lane-wise integer extended multiplication of the lower lanes producing a twice wider result than the inputs.

  T	Instruction
  i8	i16x8.extmul_low_i8x16_s
  u8	i16x8.extmul_low_i8x16_u
  i16	i32x4.extmul_low_i16x8_s
  u16	i32x4.extmul_low_i16x8_u
  i32	i64x2.extmul_low_i32x4_s
  u32	i64x2.extmul_low_i32x4_u

• function v128.extmul_high<T>(a: v128, b: v128): v128
  

  Performs the lane-wise integer extended multiplication of the higher lanes producing a twice wider result than the inputs.

  T	Instruction
  i8	i16x8.extmul_high_i8x16_s
  u8	i16x8.extmul_high_i8x16_u
  i16	i32x4.extmul_high_i16x8_s
  u16	i32x4.extmul_high_i16x8_u
  i32	i64x2.extmul_high_i32x4_s
  u32	i64x2.extmul_high_i32x4_u

Constructing constant vectors

• function i8x16(a: i8, ... , p: i8): v128
  

  Initializes a 128-bit vector from sixteen 8-bit integer values.

• function i16x8(a: i16, ..., h: i16): v128
  

  Initializes a 128-bit vector from eight 16-bit integer values.

• function i32x4(a: i32, b: i32, c: i32, d: i32): v128
  

  Initializes a 128-bit vector from four 32-bit integer values.

• function i64x2(a: i64, b: i64): v128
  

  Initializes a 128-bit vector from two 64-bit integer values.

• function f32x4(a: f32, b: f32, c: f32, d: f32): v128
  

  Initializes a 128-bit vector from four 32-bit float values.

• function f64x2(a: f64, b: f64): v128
  

  Initializes a 128-bit vector from two 64-bit float values.

Relaxed SIMD 🦄

The following instructions represent the WebAssembly Relaxed SIMD (opens new window) specification. Must be enabled with --enable relaxed-simd.

• function v128.relaxed_swizzle(a: v128, s: v128): v128
  

  Selects 8-bit lanes from a using indices in s. Indices in the range [0-15] select the i-th element of a.

  Unlike v128.swizzle, the result of an out of bounds index is implementation-defined, depending on hardware capabilities: Either 0 or a[s[i]%16].

• function v128.relaxed_trunc<T>(a: v128): v128
  

  Truncates each lane of a vector from 32-bit floating point to a 32-bit signed or unsigned integer as indicated by T.

  T	Instruction
  i32	i32x4.relaxed_trunc_f32x4_s
  u32	i32x4.relaxed_trunc_f32x4_u

  Unlike v128.trunc_sat, the result of lanes out of bounds of the target type is implementation defined, depending on hardware capabilities:

  • If the input lane contains NaN, the result is either 0 or the respective maximum integer value.
  • If the input lane contains a value otherwise out of bounds of the target type, the result is either the saturatated result or maximum integer value.

• function v128.relaxed_trunc_zero<T>(a: v128): v128
  

  Truncates each lane of a vector from 64-bit floating point to a 32-bit signed or unsigned integer as indicated by T. Unused higher integer lanes of the result are initialized to zero.

  T	Instruction
  i32	i32x4.relaxed_trunc_f64x2_s_zero
  u32	i32x4.relaxed_trunc_f64x2_u_zero

  Unlike v128.trunc_sat_zero, the result of lanes out of bounds of the target type is implementation defined, depending on hardware capabilities:

  • If the input lane contains NaN, the result is either 0 or the respective maximum integer value.
  • If the input lane contains a value otherwise out of bounds of the target type, the result is either the saturatated result or maximum integer value.

• function v128.relaxed_madd<T>(a: v128, b: v128, c: v128): v128
  

  Performs the fused multiply-add operation (a * b + c) on 32- or 64-bit floating point lanes as indicated by T.

  T	Instruction
  f32	f32x4.relaxed_madd
  f64	f64x2.relaxed_madd

  The result is implementation defined, depending on hardware capabilities:

  • Either a * b is rounded once and the final result rounded again, or
  • The expression is evaluated with higher precision and only rounded once

• function v128.relaxed_nmadd<T>(a: v128, b: v128, c: v128): v128
  

  Performs the fused negative multiply-add operation (-(a * b) + c) on 32- or 64-bit floating point lanes as indicated by T.

  T	Instruction
  f32	f32x4.relaxed_nmadd
  f64	f64x2.relaxed_nmadd

  The result is implementation defined, depending on hardware capabilities:

  • Either a * b is rounded once and the final result rounded again, or
  • The expression is evaluated with higher precision and only rounded once

• function v128.relaxed_laneselect<T>(a: v128, b: v128, m: v128): v128
  

  Selects 8-, 16-, 32- or 64-bit integer lanes as indicated by T from a or b based on masks in m.

  T	Instruction
  i8, u8	i8x16.relaxed_laneselect
  i16, u16	i16x8.relaxed_laneselect
  i32, u32	i32x4.relaxed_laneselect
  i64, u64	i64x2.relaxed_laneselect

  Behaves like v128.bitselect if masks in m do have all bits either set (result is a[i]) or unset (result is b[i]). Otherwise the result is implementation-defined, depending on hardware capabilities: If the most significant bit of m is set, the result is either bitselect(a[i], b[i], mask) or a[i], otherwise the result is b[i].

• function v128.relaxed_min<T>(a: v128, b: v128): v128
  

  Computes the minimum of each 32- or 64-bit floating point lane as indicated by T.

  T	Instruction
  f32	f32x4.relaxed_min
  f64	f64x2.relaxed_min

  Unlike v128.min, the result is implementation-defined if either value is NaN or both are -0.0 and +0.0, depending on hardware capabilities: Either a[i] or b[i].

• function v128.relaxed_max<T>(a: v128, b: v128): v128
  

  Computes the maximum of each 32- or 64-bit floating point lane as indicated by T.

  T	Instruction
  f32	f32x4.relaxed_max
  f64	f64x2.relaxed_max

  Unlike v128.max, the result is implementation-defined if either value is NaN or both are -0.0 and +0.0, depending on hardware capabilities: Either a[i] or b[i].

• function v128.relaxed_q15mulr<T>(a: v128, b: v128): v128
  

  Performs the lane-wise rounding multiplication in Q15 format ((a[i] * b[i] + (1 << (Q - 1))) >> Q where Q=15).

  T	Instruction
  i16	i16x8.relaxed_q15mulr_s

  Unlike v128.q15mulr_sat, the result is implementation-defined if both inputs are the minimum signed value: Either the minimum or maximum signed value.

• function v128.relaxed_dot<T>(a: v128, b: v128): v128
  

  Computes the dot product of two 8-bit integer lanes each, yielding lanes one size wider than the input.

  T	Instruction
  i16	i16x8.relaxed_dot_i8x16_i7x16_s

  Unlike v128.dot, if the most significant bit of b[i] is set, whether b[i] is interpreted as signed or unsigned by the intermediate multiplication is implementation-defined.

• function v128.relaxed_dot_add<T>(a: v128, b: v128, c: v128): v128
  

  Computes the dot product of two 8-bit integer lanes each, yielding lanes two sizes wider than the input with the lanes of c accumulated into the result.

  T	Instruction
  i32	i32x4.relaxed_dot_i8x16_i7x16_add_s

  Unlike v128.dot, if the most significant bit of b[i] is set, whether b[i] is interpreted as signed or unsigned by the intermediate multiplication is implementation-defined.

Inline instructions

In addition to using the generic builtins above, most WebAssembly instructions can be written directly in AssemblyScript code. For example, the following is equivalent:

// generic builtin
v128.splat<i32>(42);

// inline instruction
i32x4.splat(42);