Right rotate
The rotr
instructions, short for rotate-right, are used for performing a bitwise right-rotate.
Try it
(module
(func (export "rotate_right") (param $num i32) (param $by i32) (result i32)
;; load the number to rotate and the by how many spots
local.get $num
local.get $by
;; rotate and return the result
i32.rotr
)
)
const url = "{%wasm-url%}";
await WebAssembly.instantiateStreaming(fetch(url), { console }).then(
(result) => {
const rotate_right = result.instance.exports.rotate_right;
const res = rotate_right(0b00000000_00000000_00000000_00000111, 1);
console.log(numToBin(res));
// Expected output: "10000000_00000000_00000000_00000011"
},
);
function numToBin(num) {
return (num >>> 0)
.toString(2)
.padStart(32, "0")
.match(/.{1,8}/g)
.join("_");
}
Syntax
wasm
;; load two numbers onto the stack
i32.const 7 ;; 00000000_00000000_00000000_00000111
i32.const 1 ;; right rotate one spot
;; perform a bitwise right-rotate
i32.rotr
;; the top item on the stack will now be 2147483651
;; (10000000_00000000_00000000_00000011)
Instruction | Binary opcode |
---|---|
i32.rotr |
0x78 |
i64.rotr |
0x8a |