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Re: GCC does not support *mmintrin.h with function specific opts


On Fri, Apr 12, 2013 at 1:58 AM, Jakub Jelinek <jakub@redhat.com> wrote:
> On Thu, Apr 11, 2013 at 12:05:41PM -0700, Sriraman Tallam wrote:
>> I have attached a patch that fixes this. I have added an option
>> "-mgenerate-builtins" that will do two things.  It will define a macro
>> "__ALL_ISA__" which will expose the *intrin.h functions. It will also
>> expose all the target specific builtins.  -mgenerate-builtins will not
>> affect code generation.
>
> 1) this shouldn't be an option, either it can be made to work reliably,
>    then it should be done always, or it can't, then it shouldn't be done

Except that if there is compile time/memory consumption concerns,
users can use the option to turn it off.

> 2) have you verified that if you always generate all builtins, that the
>    builtins not supported by the ISA selected from the command line are
>    created with the right vector modes?
> 3) the *intrin.h headers in the case where the guarding macro isn't defined
>    should be surrounded by something like
>    #ifndef __FMA4__
>    #pragma GCC push options
>    #pragma GCC target("fma4")
>    #endif
>    ...
>    #ifndef __FMA4__
>    #pragma GCC pop options
>    #endif
>    so that everything that is in the headers is compiled with the ISA
>    in question

For the inline functions? (The caller functions should have the target
option), or FE needs the target option properly set?

> 4) what happens if you use the various vector types typedefed in the
>    *intrin.h headers in code that doesn't support those ISAs?  As TYPE_MODE
>    for VECTOR_TYPE is a function call, perhaps it will just be handled as
>    generic BLKmode vectors, which is desirable I think

Will the veclower pass deal with it (lowered into scalar operations)?


> 5) what happens if you use a target builtin in a function not supporting
>    the corresponding ISA, do you get proper error explaining what you are
>    doing wrong?

Yes, in ix86_expand_builtin there is a check -- that is what Sri
mentioned in a previous email.

> 6) what happens if you use some intrinsics in a function not supporting
>    the corresponding ISA?  Dunno if the inliner chooses not to inline it
>    and error out because it is always_inline, or what exactly will happen
>    then

I think it may end up with errors about unsupported builtins as above

thanks,

David

>
> For all this you certainly need testcases.
>
>         Jakub


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