x86: Add support for building {w}memmove{_chk} with explicit ISA level

1. Refactor files so that all implementations are in the multiarch
   directory
    - Moved the implementation portion of memmove sse2 from memmove.S
      to multiarch/memmove-sse2.S

    - The non-multiarch file now only includes one of the
      implementations in the multiarch directory based on the compiled
      ISA level (only used for non-multiarch builds.  Otherwise we go
      through the ifunc selector).

2. Add ISA level build guards to different implementations.
    - I.e memmove-avx2-unaligned-erms.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 (memmove-evex-unaligned-erms.S).

3. Add new multiarch/rtld-memmove.S that just include the
   non-multiarch memmove.S which will in turn select the best
   implementation based on the compiled ISA level.

4. 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.
isa raising memmove

1 files changed, 26 insertions, 0 deletions

diff --git a/sysdeps/x86_64/multiarch/memmove-shlib-compat.h b/sysdeps/x86_64/multiarch/memmove-shlib-compat.h
new file mode 100644
index 0000000000..c0793d6eef
--- /dev/null
+++ b/sysdeps/x86_64/multiarch/memmove-shlib-compat.h
@@ -0,0 +1,26 @@
+/* Copyright (C) 2016-2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#if defined SHARED && IS_IN(libc)
+# include <shlib-compat.h>
+# if SHLIB_COMPAT(libc, GLIBC_2_2_5, GLIBC_2_14)
+/* Use __memmove_{isa_level}_unaligned to support overlapping
+   addresses.  */
+compat_symbol (libc, MEMMOVE_SYMBOL (__memmove, unaligned), memcpy,
+	       GLIBC_2_2_5);
+# endif
+#endif