r = r (op) y * xi
The result is computed modulo r.len. When r.len >= a.len + b.len, no overflow occurs.
fn llmulaccLong(comptime op: AccOp, r: []Limb, a: []const Limb, b: []const Limb) void
fn llmulaccLong(comptime op: AccOp, r: []Limb, a: []const Limb, b: []const Limb) void {
assert(r.len >= a.len);
assert(a.len >= b.len);
var i: usize = 0;
while (i < b.len) : (i += 1) {
_ = llmulLimb(op, r[i..], a, b[i]);
}
}