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.
Jakub
