pmax: Wasm SIMD arithmetic instruction

The pmax instruction compares two v128 floating point value interpretations and returns a new interpretation with each output lane set to the larger of the corresponding input lanes. It is defined as a < b ? b : a, meaning that NaN in the first operand propagates to the output but NaN in the second operand does not — unlike max, which propagates NaN from either operand.

Try it

(module
  (import "console" "log" (func $log (param f32)))
  (func $main
    ;; load two v128 f32x4s onto the stack
    v128.const f32x4 52.6 101.2 78.0 9.9
    v128.const f32x4 51.9 102.0 78.1 -0.9

    ;; return a f32x4 containing the largest values from each input lane
    f32x4.pmax
    f32x4.extract_lane 3 ;; Extract a single lane
    call $log ;; log the result
  )
  (start $main)
)

const url = "{%wasm-url%}";
await WebAssembly.instantiateStreaming(fetch(url), { console });

Syntax

value_type.pmax

value_type

The type of value the instruction is being run on. The following types support pmax:

• f32x4
• f64x2

pmax

The pmax instruction. Must always be included after the value_type and a period (.).

Type

[input1, input2] -> [output]

input1

The first input value.

input2

The second input value.

output

The output value.

Binary encoding

Specifications

• WebAssembly Core Specification

See also

• max
• max_s
• max_u