Hi Segher,
on 2023/1/16 23:24, Segher Boessenkool wrote:
> On Mon, Jan 16, 2023 at 09:05:38PM +0800, Kewen.Lin wrote:
>>> The *_ok things should only be used for features that can be disabled
>>> during configuration, or features that we *want* users to be able to
>>> turn off (like FP, VMX, VSX, or HMT or QP float, that kind of thing).
>>> That gives quite enough permutations to test already, we do not need to
>>> create a whole bunch extra for no reason :-)
>>
>> Thanks for the explanation!! I meant to use powerpc_p9modulo_ok to
>> exclude those cases where we can't use -mcpu=power9, as you explained we
>> should not worry about it!?
>
> But that selector says whether modulo insns are enabled. This is not
> correct to use here. I know we have abused these things before, but it
> needs to be untangled, not made worse :-)
Makes sense, thanks for further clarifying!
>
>> Since the test point requires altivec support
>> (which is implied when specifying -mcpu=power9, I didn't explicitly specify
>> it before), I think I could use powerpc_altivec_ok to replace
>> powerpc_p9modulo_ok here, does it sound good to you?
>
> VMX can be turned off even with -mcpu=power9. So yes, it does need
> powerpc_altivec_ok. Does it need VSX even?
I think we don't need to check VSX here.
Checking VMX is for robustness and ensure it's consistent with the comment:
/* Allow -maltivec -mabi=no-altivec without warning. Altivec vector
modes only exist for GCC vector types if -maltivec. */
if (TARGET_32BIT && !TARGET_ALTIVEC_ABI && ALTIVEC_VECTOR_MODE (arg.mode))
{
if (TARGET_DEBUG_ARG)
fprintf (stderr, "function_arg_pass_by_reference: AltiVec\n");
return 1;
}
BR,
Kewen
