[glibc/azanella/clang] string: Use asm alias instead of symbol redirections for stpcpy and mempcpy

[Adhemerval Zanella <azanella@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=aaa7bfc0f918f048b9fb4d39efc3a561946f84e6

commit aaa7bfc0f918f048b9fb4d39efc3a561946f84e6
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Tue Mar 15 08:41:43 2022 -0300

    string: Use asm alias instead of symbol redirections for stpcpy and mempcpy
    
    Commit 939da411433 added symbols redirections to handle ISO C
    namespace, however some compiler does not support to redeclare the
    function prototype.  Moving these defintions to exported header
    it not a good practice (it exposes a internal implementation and
    it would require to add macros to define it only internally).
    
    Instead this patch replaces the symbol redirections by direct asm
    aliases, as done to handle libcall generation done by compiler on
    some loop optimizations. The only issue is sparc binutils generates
    an extra __mempcpy plt not called anywhere in the code, which indicates
    a binutils issue (this is added in the localplt.data for now).
    
    Checked on most of affected ABIs.

Diff:
---
 include/string.h                                    | 4 ++--
 sysdeps/unix/sysv/linux/sparc/sparc64/localplt.data | 3 +++
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/include/string.h b/include/string.h
index 21f641a413..44c4049053 100644
--- a/include/string.h
+++ b/include/string.h
@@ -176,8 +176,8 @@ extern __typeof (strsep) strsep attribute_hidden;
   && !defined NO_MEMPCPY_STPCPY_REDIRECT
 /* Redirect calls to __builtin_mempcpy and __builtin_stpcpy to call
    __mempcpy and __stpcpy if not inlined.  */
-extern __typeof (mempcpy) mempcpy __asm__ ("__mempcpy");
-extern __typeof (stpcpy) stpcpy __asm__ ("__stpcpy");
+__asm__ ("mempcpy = __mempcpy");
+__asm__ ("stpcpy = __stpcpy");
 #endif
 
 extern void *__memcpy_chk (void *__restrict __dest,
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/localplt.data b/sysdeps/unix/sysv/linux/sparc/sparc64/localplt.data
index 6a216f3a5a..21a5fe65ba 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc64/localplt.data
+++ b/sysdeps/unix/sysv/linux/sparc/sparc64/localplt.data
@@ -16,6 +16,9 @@ libc.so: calloc
 libc.so: free
 libc.so: malloc
 libc.so: realloc
+# Unreferenced PLT created by the symbols aliases used to redirect
+# the compiler generated mempcpy/stpcyp calls done by builtin usage.
+libc.so: __mempcpy
 libm.so: matherr
 # The TLS-enabled version of these functions is interposed from libc.so.
 ld.so: _dl_signal_error