Count trailing zeros
The ctz
instructions, short for count trailing zeros, are used to count the amount of zeros at the end of the numbers binary representation.
Try it
(module
(func (export "trailing0") (param $num i32) (result i32)
;; load number onto the stack
local.get $num
;; check how many trailing zeros and return the result
i32.ctz
)
)
const url = "{%wasm-url%}";
await WebAssembly.instantiateStreaming(fetch(url), { console }).then(
(result) => {
const trailing0 = result.instance.exports.trailing0;
console.log(
`Trailing zeros: ${trailing0(0b00000000_10000000_00000000_00000000)}`,
);
// Expected output: "Trailing zeros: 23"
},
);
Syntax
wasm
;; load a number onto the stack
i32.const 8388608 ;; 00000000_10000000_00000000_00000000
;; count trailing zeros
i32.ctz
;; the top item on the stack will now be 23
Instruction | Binary opcode |
---|---|
i32.ctz |
0x68 |
i64.ctz |
0x7a |