Use generic __ifunc for SPARC

[David Miller]

From: Joseph Myers <joseph@codesourcery.com>
Date: Tue, 26 Sep 2017 18:17:06 +0000

> glibc fails to build with GCC mainline for SPARC because of the use of
> manually-created IFUNCs, which fail the tests of compatibility of
> function alias types.  This patch changes sparc-ifunc.h to use the
> generic __ifunc in defining sparc_libm_ifunc.  The generic __ifunc can
> use the GCC ifunc attribute when available, so ensuring
> type-correctness as well as better debug info than when setting symbol
> types in asm statements.
> 
> Note that for this to fix the build with GCC mainline the GCC patch
> <https://gcc.gnu.org/ml/gcc-patches/2017-09/msg01779.html>, or
> building GCC with --enable-gnu-indirect-function, is also needed.
> 
> Tested (compilation only) with build-many-glibcs.py (sparc64-linux-gnu
> and sparcv9-linux-gnu, with GCC 8 with the above patch, and also with
> GCC 7).
> 
> 2017-09-26  Joseph Myers  <joseph@codesourcery.com>
> 
> 	* sysdeps/sparc/sparc-ifunc.h [!__ASSEMBLER__] (sparc_libm_ifunc):
> 	Define using __ifunc.

Looks good.