[glibc] string: Improve generic strrchr with memrchr and strlen

[glibc] string: Improve generic strrchr with memrchr and strlen

[Adhemerval Zanella]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=167f6230af97690985ccbc9b3026a7c32ec2d6e9

commit 167f6230af97690985ccbc9b3026a7c32ec2d6e9
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Thu Feb 2 13:44:13 2023 -0300

    string: Improve generic strrchr with memrchr and strlen
    
    Now that both strlen and memrchr have word vectorized implementation,
    it should be faster to implement strrchr based on memrchr over the
    string length instead of calling strchr on a loop.
    
    Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc-linux-gnu,
    and powerpc64-linux-gnu by removing the arch-specific assembly
    implementation and disabling multi-arch (it covers both LE and BE
    for 64 and 32 bits).

Diff:
---
 string/strrchr.c | 18 +-----------------
 1 file changed, 1 insertion(+), 17 deletions(-)

diff --git a/string/strrchr.c b/string/strrchr.c
index 3c6e715d3b..7b76dea4e0 100644
--- a/string/strrchr.c
+++ b/string/strrchr.c
@@ -27,23 +27,7 @@
 char *
 STRRCHR (const char *s, int c)
 {
-  const char *found, *p;
-
-  c = (unsigned char) c;
-
-  /* Since strchr is fast, we use it rather than the obvious loop.  */
-
-  if (c == '\0')
-    return strchr (s, '\0');
-
-  found = NULL;
-  while ((p = strchr (s, c)) != NULL)
-    {
-      found = p;
-      s = p + 1;
-    }
-
-  return (char *) found;
+  return __memrchr (s, c, strlen (s) + 1);
 }
 
 #ifdef weak_alias