Branch Hinting

branch-hinting provides likely() and unlikely() helpers plus a transform that emits the metadata.code.branch_hint custom section in the final wasm.

Import

import { likely, unlikely } from "as-labs/branch-hinting";

Example

export function classify(n: i32): i32 {
  if (likely(n > 0)) return 1;
  if (unlikely(n < 0)) return -1;
  return 0;
}

Transform

asc assembly/index.ts --transform as-labs/branch-hinting -o build/module.wasm

Behavior

• likely() emits a \01 branch hint
• unlikely() emits a \00 branch hint
• the helper wrappers are erased during compilation
• the transform currently targets direct statement conditions such as if, while, do, and for

Verification

The reliable verification target is the binary itself.

• inspect the final .wasm for metadata.code.branch_hint
• do not rely on generic wasm2wat output to re-render hint annotations
• if you want to inspect the annotation in text form, use transform-generated .wat output rather than decompiling the binary later