Clean up the IFUNC implementations for powerpc in order to remove
unneeded macro definitions.
Tested on ppc64le with and without --disable-multi-arch flag.
* sysdeps/powerpc/powerpc64/multiarch/strcasecmp_l-power7.S: Define
the implementation-specific function name and remove unneeded
macros definition.
* sysdeps/powerpc/powerpc64/multiarch/strcmp-power7.S: Likewise.
* sysdeps/powerpc/powerpc64/multiarch/strcmp-power8.S Likewise.
* sysdeps/powerpc/powerpc64/multiarch/strcmp-power9.S: Likewise.
* sysdeps/powerpc/powerpc64/multiarch/strcmp-ppc64.S: Likewise.
* sysdeps/powerpc/powerpc64/multiarch/strncmp-power4.S: Likewise.
* sysdeps/powerpc/powerpc64/multiarch/strncmp-power7.S: Likewise.
* sysdeps/powerpc/powerpc64/multiarch/strncmp-power8.S: Likewise.
* sysdeps/powerpc/powerpc64/multiarch/strncmp-power9.S: Likewise.
* sysdeps/powerpc/powerpc64/multiarch/strncmp-ppc64.S: Likewise.
* sysdeps/powerpc/powerpc64/power4/strncmp.S: Set a default function
name if not defined and pass as parameter to macros accordingly.
* sysdeps/powerpc/powerpc64/power7/strcmp.S: Likewise.
* sysdeps/powerpc/powerpc64/power7/strncmp.S: Likewise.
* sysdeps/powerpc/powerpc64/power8/strcmp.S: Likewise.
* sysdeps/powerpc/powerpc64/power8/strncmp.S: Likewise.
* sysdeps/powerpc/powerpc64/power9/strcmp.S: Likewise.
* sysdeps/powerpc/powerpc64/power9/strncmp.S: Likewise.
* sysdeps/powerpc/powerpc64/strcmp.S: Likewise.
* sysdeps/powerpc/powerpc64/strncmp.S: Likewise.
For strings >16B and <32B existing algorithm takes more time than default
implementation when strings are placed closed to end of page. This is due
to byte by byte access for handling page cross. This is improved by
following >32B code path where the address is adjusted to aligned memory
before doing load doubleword operation instead of loading bytes.
Tested on powerpc64 and powerpc64le.
This patch adds an optimized POWER8 strcmp using unaligned accesses.
The algorithm first check the initial 16 bytes, then align the first
function source and uses unaligned loads on second argument only.
Aditional checks for page boundaries are done for unaligned cases
