1. Add default ISA level selection in non-multiarch/rtld
implementations.
2. Add ISA level build guards to different implementations.
- I.e strcmp-avx2.S which is ISA level 3 will only build if
compiled ISA level <= 3. Otherwise there is no reason to
include it as we will always use one of the ISA level 4
implementations (strcmp-evex.S).
3. Refactor the ifunc selector and ifunc implementation list to use
the ISA level aware wrapper macros that allow functions below the
compiled ISA level (with a guranteed replacement) to be skipped.
Tested with and without multiarch on x86_64 for ISA levels:
{generic, x86-64-v2, x86-64-v3, x86-64-v4}
And m32 with and without multiarch.
Since wcsnlen.S uses pminud which is the part of SSE4.1, move wcsnlen.S
to multiarch/wcsnlen-sse4_1.S.
* sysdeps/x86_64/multiarch/Makefile (sysdep_routines): Add
wcsnlen-sse4_1 and wcsnlen-c.
* sysdeps/x86_64/multiarch/ifunc-impl-list.c
(__libc_ifunc_impl_list): Test __wcsnlen_sse4_1 and
__wcsnlen_sse2.
* sysdeps/x86_64/multiarch/ifunc-sse4_1.h: New file.
* sysdeps/x86_64/multiarch/wcsnlen-c.c: Likewise.
* sysdeps/x86_64/multiarch/wcsnlen-sse4_1.S: Likewise.
* sysdeps/x86_64/multiarch/wcsnlen.c: Likewise.
* sysdeps/x86_64/wcsnlen.S: Removed.
The difference between strlen and wcslen is byte vs int. We can
replace pminub and pcmpeqb with pminud and pcmpeqd to turn strlen
into wcslen.
* sysdeps/x86_64/strlen.S (PMINU): New.
(PCMPEQ): Likewise.
(SHIFT_RETURN): Likewise.
(FIND_ZERO): Replace pcmpeqb with PCMPEQ.
(strlen): Add SHIFT_RETURN before ret. Replace pcmpeqb and
pminub with PCMPEQ and PMINU.
* sysdeps/x86_64/wcsnlen.S: New file.
