x86: Add support to build st{p|r}{n}{cpy|cat} with explicit ISA level

1. Add default ISA level selection in non-multiarch/rtld
   implementations.

2. Add ISA level build guards to different implementations.
    - I.e strcpy-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 (strcpy-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.

1 files changed, 13 insertions, 10 deletions

diff --git a/sysdeps/x86_64/multiarch/strcpy-sse2.S b/sysdeps/x86_64/multiarch/strcpy-sse2.S
index 8b5db8b13d..e29b411314 100644
--- a/sysdeps/x86_64/multiarch/strcpy-sse2.S
+++ b/sysdeps/x86_64/multiarch/strcpy-sse2.S
@@ -1,5 +1,5 @@
-/* strcpy optimized with SSE2.
-   Copyright (C) 2017-2022 Free Software Foundation, Inc.
+/* strcpy/stpcpy implementation for x86-64.
+   Copyright (C) 2002-2022 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
@@ -16,13 +16,15 @@
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
-#if IS_IN (libc)
-# ifndef STRCPY
+#include <isa-level.h>
+
+#if ISA_SHOULD_BUILD (1)
+
+# include <sysdep.h>
+
+# ifndef STPCPY
 #  define STRCPY __strcpy_sse2
 # endif
-#endif
-
-#include <sysdep.h>
 
 	.text
 ENTRY (STRCPY)
@@ -144,10 +146,11 @@ ENTRY (STRCPY)
 	jmp	3b		/* and look at next two bytes in %rax.  */
 
 4:
-#ifdef USE_AS_STPCPY
+# ifdef USE_AS_STPCPY
 	movq	%rdx, %rax	/* Destination is return value.  */
-#else
+# else
 	movq	%rdi, %rax	/* Source is return value.  */
-#endif
+# endif
 	retq
 END (STRCPY)
+#endif