[glibc] Benchtests: Improve memrchr benchmarks

[Noah Goldstein <nwg@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=d0370d992e5e7b4a8843e8e130f6c86b483ab7d0

commit d0370d992e5e7b4a8843e8e130f6c86b483ab7d0
Author: Noah Goldstein <goldstein.w.n@gmail.com>
Date:   Mon Jun 6 21:11:29 2022 -0700

    Benchtests: Improve memrchr benchmarks
    
    Add a second iteration for memrchr to set `pos` starting from the end
    of the buffer.
    
    Previously `pos` was only set relative to the beginning of the
    buffer. This isn't really useful for memrchr because the beginning
    of the search space is (buf + len).
    Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

Diff:
---
 benchtests/bench-memchr.c | 110 +++++++++++++++++++++++++++-------------------
 1 file changed, 65 insertions(+), 45 deletions(-)

diff --git a/benchtests/bench-memchr.c b/benchtests/bench-memchr.c
index 4d7212332f..0facda2fa0 100644
--- a/benchtests/bench-memchr.c
+++ b/benchtests/bench-memchr.c
@@ -76,7 +76,7 @@ do_one_test (json_ctx_t *json_ctx, impl_t *impl, const CHAR *s, int c,
 
 static void
 do_test (json_ctx_t *json_ctx, size_t align, size_t pos, size_t len,
-	 int seek_char)
+	 int seek_char, int invert_pos)
 {
   size_t i;
 
@@ -96,7 +96,10 @@ do_test (json_ctx_t *json_ctx, size_t align, size_t pos, size_t len,
 
   if (pos < len)
     {
-      buf[align + pos] = seek_char;
+      if (invert_pos)
+	buf[align + len - pos] = seek_char;
+      else
+	buf[align + pos] = seek_char;
       buf[align + len] = -seek_char;
     }
   else
@@ -109,6 +112,7 @@ do_test (json_ctx_t *json_ctx, size_t align, size_t pos, size_t len,
   json_attr_uint (json_ctx, "pos", pos);
   json_attr_uint (json_ctx, "len", len);
   json_attr_uint (json_ctx, "seek_char", seek_char);
+  json_attr_uint (json_ctx, "invert_pos", invert_pos);
 
   json_array_begin (json_ctx, "timings");
 
@@ -123,6 +127,7 @@ int
 test_main (void)
 {
   size_t i;
+  int repeats;
   json_ctx_t json_ctx;
   test_init ();
 
@@ -142,53 +147,68 @@ test_main (void)
 
   json_array_begin (&json_ctx, "results");
 
-  for (i = 1; i < 8; ++i)
+  for (repeats = 0; repeats < 2; ++repeats)
     {
-      do_test (&json_ctx, 0, 16 << i, 2048, 23);
-      do_test (&json_ctx, i, 64, 256, 23);
-      do_test (&json_ctx, 0, 16 << i, 2048, 0);
-      do_test (&json_ctx, i, 64, 256, 0);
-
-      do_test (&json_ctx, getpagesize () - 15, 64, 256, 0);
+      for (i = 1; i < 8; ++i)
+	{
+	  do_test (&json_ctx, 0, 16 << i, 2048, 23, repeats);
+	  do_test (&json_ctx, i, 64, 256, 23, repeats);
+	  do_test (&json_ctx, 0, 16 << i, 2048, 0, repeats);
+	  do_test (&json_ctx, i, 64, 256, 0, repeats);
+
+	  do_test (&json_ctx, getpagesize () - 15, 64, 256, 0, repeats);
 #ifdef USE_AS_MEMRCHR
-      /* Also test the position close to the beginning for memrchr.  */
-      do_test (&json_ctx, 0, i, 256, 23);
-      do_test (&json_ctx, 0, i, 256, 0);
-      do_test (&json_ctx, i, i, 256, 23);
-      do_test (&json_ctx, i, i, 256, 0);
+	  /* Also test the position close to the beginning for memrchr.  */
+	  do_test (&json_ctx, 0, i, 256, 23, repeats);
+	  do_test (&json_ctx, 0, i, 256, 0, repeats);
+	  do_test (&json_ctx, i, i, 256, 23, repeats);
+	  do_test (&json_ctx, i, i, 256, 0, repeats);
 #endif
-    }
-  for (i = 1; i < 8; ++i)
-    {
-      do_test (&json_ctx, i, i << 5, 192, 23);
-      do_test (&json_ctx, i, i << 5, 192, 0);
-      do_test (&json_ctx, i, i << 5, 256, 23);
-      do_test (&json_ctx, i, i << 5, 256, 0);
-      do_test (&json_ctx, i, i << 5, 512, 23);
-      do_test (&json_ctx, i, i << 5, 512, 0);
-
-      do_test (&json_ctx, getpagesize () - 15, i << 5, 256, 23);
-    }
-  for (i = 1; i < 32; ++i)
-    {
-      do_test (&json_ctx, 0, i, i + 1, 23);
-      do_test (&json_ctx, 0, i, i + 1, 0);
-      do_test (&json_ctx, i, i, i + 1, 23);
-      do_test (&json_ctx, i, i, i + 1, 0);
-      do_test (&json_ctx, 0, i, i - 1, 23);
-      do_test (&json_ctx, 0, i, i - 1, 0);
-      do_test (&json_ctx, i, i, i - 1, 23);
-      do_test (&json_ctx, i, i, i - 1, 0);
-
-      do_test (&json_ctx, getpagesize () - 15, i, i - 1, 23);
-      do_test (&json_ctx, getpagesize () - 15, i, i - 1, 0);
-
-      do_test (&json_ctx, getpagesize () - 15, i, i + 1, 23);
-      do_test (&json_ctx, getpagesize () - 15, i, i + 1, 0);
+	}
+      for (i = 1; i < 8; ++i)
+	{
+	  do_test (&json_ctx, i, i << 5, 192, 23, repeats);
+	  do_test (&json_ctx, i, i << 5, 192, 0, repeats);
+	  do_test (&json_ctx, i, i << 5, 256, 23, repeats);
+	  do_test (&json_ctx, i, i << 5, 256, 0, repeats);
+	  do_test (&json_ctx, i, i << 5, 512, 23, repeats);
+	  do_test (&json_ctx, i, i << 5, 512, 0, repeats);
+
+	  do_test (&json_ctx, getpagesize () - 15, i << 5, 256, 23, repeats);
+	}
+      for (i = 1; i < 32; ++i)
+	{
+	  do_test (&json_ctx, 0, i, i + 1, 23, repeats);
+	  do_test (&json_ctx, 0, i, i + 1, 0, repeats);
+	  do_test (&json_ctx, i, i, i + 1, 23, repeats);
+	  do_test (&json_ctx, i, i, i + 1, 0, repeats);
+	  do_test (&json_ctx, 0, i, i - 1, 23, repeats);
+	  do_test (&json_ctx, 0, i, i - 1, 0, repeats);
+	  do_test (&json_ctx, i, i, i - 1, 23, repeats);
+	  do_test (&json_ctx, i, i, i - 1, 0, repeats);
+
+	  do_test (&json_ctx, getpagesize () / 2, i, i + 1, 23, repeats);
+	  do_test (&json_ctx, getpagesize () / 2, i, i + 1, 0, repeats);
+	  do_test (&json_ctx, getpagesize () / 2 + i, i, i + 1, 23, repeats);
+	  do_test (&json_ctx, getpagesize () / 2 + i, i, i + 1, 0, repeats);
+	  do_test (&json_ctx, getpagesize () / 2, i, i - 1, 23, repeats);
+	  do_test (&json_ctx, getpagesize () / 2, i, i - 1, 0, repeats);
+	  do_test (&json_ctx, getpagesize () / 2 + i, i, i - 1, 23, repeats);
+	  do_test (&json_ctx, getpagesize () / 2 + i, i, i - 1, 0, repeats);
+
+	  do_test (&json_ctx, getpagesize () - 15, i, i - 1, 23, repeats);
+	  do_test (&json_ctx, getpagesize () - 15, i, i - 1, 0, repeats);
+
+	  do_test (&json_ctx, getpagesize () - 15, i, i + 1, 23, repeats);
+	  do_test (&json_ctx, getpagesize () - 15, i, i + 1, 0, repeats);
+
 #ifdef USE_AS_MEMRCHR
-      /* Also test the position close to the beginning for memrchr.  */
-      do_test (&json_ctx, 0, 1, i + 1, 23);
-      do_test (&json_ctx, 0, 2, i + 1, 0);
+	  do_test (&json_ctx, 0, 1, i + 1, 23, repeats);
+	  do_test (&json_ctx, 0, 2, i + 1, 0, repeats);
+#endif
+	}
+#ifndef USE_AS_MEMRCHR
+      break;
 #endif
     }