[RFC PATCH 1/2] RISC-V: Add VLA support and Fortran declarations to RVV libmvec

[Florian Weimer]

* zhou yanan:

> In-Reply-To: <af3aceaa-dcf1-4fa6-ad7e-a7fd7444a0c5@spacemit.com>
> References: <af3aceaa-dcf1-4fa6-ad7e-a7fd7444a0c5@spacemit.com>
>
> Hi Zhijin, 
> Rivos libvecm repository has been re-licensed under the MIT license, which is believed to be compatible with glibc's LGPL-2.1+.
> Based on the ongoing psABI discussion:
> https://github.com/riscv-non-isa/riscv-elf-psabi-doc/pull/455
> this series implements the following changes:

> 1. Mangling update: change the vector math symbol prefix from
> _ZGV<lmul>N<simdlen>v_* to _ZGVr<lmul>N<simdlen>v_*, adding the
> architecture tag <r> as specified in the psABI draft.

Ugh, we can't do that.  Why was this added to the glibc ABI when the
symbols were still in draft status?

We need to keep the old symbols as compatibility symbols, or bump
soname on libmvec (so that the old ABI can be provided by an older
version of glibc, possibly after removing GLIBC_PRIVATE dependencies).
We should delay these changes until the ABI is final.