[klibc] Debian #943425: klibc: [s390x] setjmp/longjmp do not save/restore all registers in use
krebbel at linux.ibm.com
Wed May 5 23:05:40 PDT 2021
On 5/5/21 7:32 PM, Thorsten Glaser wrote:
> Hi Andreas,
>>>> Jessica Clarke brought out docs saying f8‥f15 must be saved, the
>>>> other FPU registers not:
>> I can confirm this. It is f8-f15 for the z/Architecture (64 bit).
>> It is f1, f3, f5, f7 for the ESA
>> architecture (32 bit) which is still supported by Glibc and GCC.
> Is this what we know as s390 in Debian? (klibc saves f4 and f6 there
> currently. If so, this also needs to change.)
f4 and f6 is correct for 32 bit. Sorry for the confusion. Here a link to the 32 bit ABI:
>>>> … GCC chooses to allocate an FPU register for a pointer value.
>> GCC will put integer values into vector registers for
>> auto-vectorization or for spilling. We also use call-clobbered FPRs as
>> save slots for GPRs in leaf-functions if can get rid of allocating a
>> stack frame that way.
> Ah, interesting. Thanks!
>> The vector registers are call-clobbered - exactly for the reason of
>> setjmp / longjmp. Only f8-f15 need to be saved.
>> You can find the latest version of our ABI here:
>> However, it is still lacking the vector ABI extension. I wrote a
>> document for that which we use internally and we are working on
>> integrating it into the publicly available version.
> OK, thanks for the information!
>>>> @klibc list: as indicated earlier, I can provide a patch if needed
>>>> (though it should be obvious).
> hpa, maks, bwh: any of you taking these two or should I send patches
> and possibly NMU klibc in Debian?
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