replace_lane: Wasm SIMD conversion instruction

The replace_lane SIMD conversion instruction replaces the specified lane of a v128 value interpretation with a new value and returns the resulting v128 value interpretation.

Try it

(module
  (import "console" "log" (func $log (param f64)))
  (func $main
    v128.const f64x2 1200000 3456789
    f64.const 777777

    f64x2.replace_lane 1
    f64x2.extract_lane 1
    call $log ;; log the result
  )
  (start $main)
)

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

Syntax

value_type.replace_lane index

value_type

The type of value the instruction is being run on. The following v128 value interpretations support replace_lane:

i8x16
i16x8
i32x4
i64x2
f32x4
f64x2

replace_lane

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

index

The index of the lane that you want to replace.

Type

[input, replace_value] -> [output]

input: The input v128 value interpretation.
replace_value: The value that you want to replace the lane with.
output: The output v128 value interpretation.

Binary encoding

Instruction	Binary format	Example text => binary
`i8x16.replace_lane`	`0xfd 23:u32 l:lane_idx`	`i8x16.replace_lane 3` => `0xfd 0x17 0x03`
`i16x8.replace_lane`	`0xfd 26:u32 l:lane_idx`	`i16x8.replace_lane 3` => `0xfd 0x1a 0x03`
`i32x4.replace_lane`	`0xfd 28:u32 l:lane_idx`	`i32x4.replace_lane 3` => `0xfd 0x1c 0x03`
`i64x2.replace_lane`	`0xfd 30:u32 l:lane_idx`	`i64x2.replace_lane 1` => `0xfd 0x1e 0x01`
`f32x4.replace_lane`	`0xfd 32:u32 l:lane_idx`	`f32x4.replace_lane 3` => `0xfd 0x20 0x03`
`f64x2.replace_lane`	`0xfd 34:u32 l:lane_idx`	`f64x2.replace_lane 1` => `0xfd 0x22 0x01`

Specifications

WebAssembly Core Specification