sub_sat_u: Wasm SIMD arithmetic instruction

The sub_sat_u SIMD arithmetic instruction performs a saturating subtraction of two unsigned v128 value interpretations — clamping the output to the range allowed by the value type. Each lane of the output value is the result of subtracting the corresponding lane of the second input from the corresponding lane of the first input.

Try it

(module
  (import "console" "log" (func $log (param i32)))
  (func $main
    v128.const i16x8 4 6 16 8 23 65 82 9
    v128.const i16x8 0 25 2 30 2 34 45 80

    i16x8.sub_sat_u
    i16x8.extract_lane_s 7
    call $log ;; log the result
  )
  (start $main)
)

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

Saturation means that the output values are clamped to the upper and lower values allowed by the value interpretation instead of wrapping. Allowed output values are:

• i8x16.sub_sat_u: 0 to 255 (the full range of an unsigned 8-bit integer)
• i16x8.sub_sat_u: 0 to 65,535 (the full range of an unsigned 16-bit integer)

Syntax

value_type.sub_sat_u

value_type

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

• i8x16
• i16x8

sub_sat_u

The sub_sat_u 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

• sub