On Tue, Jun 10, 2008 at 8:48 AM, Jan Hubicka <[EMAIL PROTECTED]> wrote:
>> On Tue, Jun 10, 2008 at 8:11 AM, Jakub Jelinek <[EMAIL PROTECTED]> wrote:
>> > On Tue, Jun 10, 2008 at 04:50:14PM +0200, Jan Hubicka wrote:
>> >> 1) make __m256 passed on stack on variadic functions and in registers
>> >> otherwse. Then we don't need to worry about varargs changes at all.
>> >> This will break unprototyped calls.
>> >> 2) extend rax to pass info about if __m256 registers are present and
>> >> upper half needs to be saved.
>> >> This will break passing __m256 arguments to functions with prologues
>> >> compiled with legacy compiler that will do wild jump. All other cases
>> >> should work
>> >> 3) Save upper halves whenever we want to save SSE registers. This will
>> >> break calling variadic functions compiled with __m256 support in.
>> >>
>> >> I guess either 1) or 2) is fine for me, as I told earlier, I am not big
>> >> fan of 3). I guess 1) is easier and probably make more sense?
>> >
>> > I vote for 1), though I think it should be passed on stack only for ...
>> > args. E.g. for
>> > void foo (__m256 x, ...);
>> > void bar (__m256 x, __m256 y, __m256 z)
>> > {
>> > foo (x, y, z);
>> > }
>> > the first argument would be passed in %ymm0, while the unnamed arguments
>> > y and z would be pushed to stack.
>> >
>>
>> I agree. We will add testcases for whatever psABI extension we have
>> chosen.
>
> I guess we all agree on passing variadic arguments on stack (that is
> only those belonging on ...) and rest in registers. It seems easiest in
> regard to future register set extensions too. Only negative thing is
> that calls to variadic functions will become bit longer, but I guess it
> is not big deal. (the fact that register passing conventions are shorter
> and variadic functions tends to be called many times was also original
> motivation to support register passing on pretty much everything for
> varargs in psABI)
>
> Would you mind preparing psABI patch too?
>
We will have an AVX BoF at gcc summit next week. We have
reserved 5:15pm to 6:15pm on Wednesday. We will submit the
psABI patch before gcc summit.
Thanks.
--
H.J.
