Re: Debian #943425: [s390x] setjmp/longjmp do not save/restore all registers in use

Dixi quod…

>Jessica Clarke brought out docs saying f8‥f15 must be saved, the
>other FPU registers not:

This needs to be fixed in klibc.

>>• klibc does not really support the FPU anyway
>
>… GCC chooses to allocate an FPU register for a pointer value.

This is a curiosity.

>>• the half of v10 that equals f10 just HAPPENS to be saved by
>>  glibc, but what if the upper half, that is outside of the FPU,
>>  is used?
>
>The question here is, does GCC only use the halves of the half
>of the vector registers that match the FPU registers?

04:41⎜«jrtc27:#debian-x32» hephaistor: re s390x vector registers, reading the gcc and llvm sources they're
     ⎜    all call-clobbered by default, only the float parts are call-saved
04:41⎜«jrtc27:#debian-x32» so that's why setjmp/longjmp don't need to save/restore them
04:42⎜«jrtc27:#debian-x32» there *is* a vector calling convention, but it's not the default for the ABI,
     ⎜    it's opt-in, and setjmp/longjmp won't be annotated as such

So we indeed need to only save the registers glibc does.

>@klibc list: as indicated earlier, I can provide a patch if needed
>(though it should be obvious).

bye,
//mirabilos
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