vectorConstAssumeCapacity

fn vectorConstAssumeCapacity(self: *Builder, ty: Type, vals: []const Constant) Constant {
    assert(ty.isVector(self));
    assert(ty.vectorLen(self) == vals.len);
    for (vals) |val| assert(ty.childType(self) == val.typeOf(self));

    for (vals[1..]) |val| {
        if (vals[0] != val) break;
    } else return self.splatConstAssumeCapacity(ty, vals[0]);
    for (vals) |val| {
        if (!val.isZeroInit(self)) break;
    } else return self.zeroInitConstAssumeCapacity(ty);

    const result = self.getOrPutConstantAggregateAssumeCapacity(.vector, ty, vals);
    return result.constant;
}