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Re: [PATCH RFC] add generic expansion for MULT_HIGHPART_EXP


Hi,

On Mon, Aug 20, 2018 at 1:46 PM Alexander Monakov <amonakov@ispras.ru> wrote:
> > So - how difficult is it to fix BRIG to not use MULT_HIGHPART_EXPR if
> > not supported?
>
> Pekka, can you comment? I think you have fallback paths for vector types
> only at the moment?

I think it involves pretty much moving the code of your patch to the
BRIG frontend.
To me it'd look a bit wrong in terms of "division of responsibilities"
as this is not really
frontend-specific as far as I understand (even if BRIG/HSAIL happened
to be the only language
supporting them currently).

> Does BRIG have mult-highpart for 64-bit integers? On 32-bit targets we
> won't be able to easily expand them (but on 64-bit targets it is fine).

Yes it does. 32b targets are not high priority for BRIG FE at this
point, so I wouldn't
worry about this as we assume HSA's "large" model is used, so this is likely not
the only problem when trying to generate for 32b machines.

> For scalar types I think we should prefer to implement a generic expansion
> rather than have the frontend query the backend. For vector types I am not
> sure.

In my relatively gcc-uneducated humble opinion these both belong more
naturally to a
target-specific expansion or "legalization" pass, which tries to
convert tree nodes to what the target
can support.

BR,
Pekka


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