// implemented in arith_$GOARCH.s

// addVV should be an internal detail,
// but widely used packages access it using linkname.
// Notable members of the hall of shame include:
//   - github.com/remyoudompheng/bigfft
//
// Do not remove or change the type signature.
// See go.dev/issue/67401.
//
//go:linkname addVV
//go:noescape
func addVV(z, x, y []Word) (c Word)

// subVV should be an internal detail,