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Re: [RFC PATCH 1/2] Aarch64: Add simd exp/expf ABI symbols
- From: Szabolcs Nagy <Szabolcs dot Nagy at arm dot com>
- To: Tulio Magno Quites Machado Filho <tuliom at ascii dot art dot br>, GNU C Library <libc-alpha at sourceware dot org>, Steve Ellcey <sellcey at marvell dot com>
- Cc: nd <nd at arm dot com>, Francesco Petrogalli <Francesco dot Petrogalli at arm dot com>
- Date: Tue, 9 Jul 2019 08:52:32 +0000
- Subject: Re: [RFC PATCH 1/2] Aarch64: Add simd exp/expf ABI symbols
- References: <0ae3af1b-cb2b-367f-8b86-f39971498291@arm.com> <877e8scsov.fsf@linux.ibm.com>
On 08/07/2019 19:00, Tulio Magno Quites Machado Filho wrote:
> Szabolcs Nagy <Szabolcs.Nagy@arm.com> writes:
>
>> diff --git a/sysdeps/aarch64/fpu/Versions b/sysdeps/aarch64/fpu/Versions
>> new file mode 100644
>> index 0000000000..da36f3c495
>> --- /dev/null
>> +++ b/sysdeps/aarch64/fpu/Versions
>> @@ -0,0 +1,5 @@
>> +libmvec {
>> + GLIBC_2.30 {
>> + _ZGVnN2v_exp; _ZGVnN4v_expf;
>
> The prefix _ZGV is reserved for guard variables in the C++ ABI [1] [2].
> How do you plan to avoid a conflict there?
>
> [1] https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/cp/mangle.c;#l4242
> [2] https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/testsuite/g%2B%2B.dg/abi/aarch64_guard1.C
i noticed that too when this was designed, but it
was decided that it's better to use the intel vector
function mangling on aarch64 too than to introduce
target specific mangling.
i don't know how serious such a conflict is, nor why
intel chose a clearly conflicting prefix. i assumed
c++ folks were aware of the issue and accepted it
when the intel vector abi was introduced.