[glibc] bench-strcmp.c: Add workloads on page boundary

[glibc] bench-strcmp.c: Add workloads on page boundary

[H.J. Lu]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=06e95b93f0bb5943363ad3dcf0cd0fb9d8613b61

commit 06e95b93f0bb5943363ad3dcf0cd0fb9d8613b61
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Thu Jun 11 09:00:12 2020 -0700

    bench-strcmp.c: Add workloads on page boundary
    
    Add strcmp workloads on page boundary.

Diff:
---
 benchtests/bench-strcmp.c | 56 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/benchtests/bench-strcmp.c b/benchtests/bench-strcmp.c
index 47d0a35299..c6f8446978 100644
--- a/benchtests/bench-strcmp.c
+++ b/benchtests/bench-strcmp.c
@@ -144,6 +144,60 @@ do_test (json_ctx_t *json_ctx, size_t align1, size_t align2, size_t len, int
   json_element_object_end (json_ctx);
 }
 
+static void
+do_one_test_page_boundary (json_ctx_t *json_ctx, CHAR *s1, CHAR *s2,
+			   size_t align1, size_t align2, size_t len,
+			   int exp_result)
+{
+  json_element_object_begin (json_ctx);
+  json_attr_uint (json_ctx, "length", (double) len);
+  json_attr_uint (json_ctx, "align1", (double) align1);
+  json_attr_uint (json_ctx, "align2", (double) align2);
+  json_array_begin (json_ctx, "timings");
+  FOR_EACH_IMPL (impl, 0)
+    do_one_test (json_ctx, impl, s1, s2, exp_result);
+  json_array_end (json_ctx);
+  json_element_object_end (json_ctx);
+}
+
+static void
+do_test_page_boundary (json_ctx_t *json_ctx)
+{
+  /* To trigger bug 25933, we need a size that is equal to the vector
+     length times 4. In the case of AVX2 for Intel, we need 32 * 4.  We
+     make this test generic and run it for all architectures as additional
+     boundary testing for such related algorithms.  */
+  size_t size = 32 * 4;
+  size_t len;
+  CHAR *s1 = (CHAR *) (buf1 + (BUF1PAGES - 1) * page_size);
+  CHAR *s2 = (CHAR *) (buf2 + (BUF1PAGES - 1) * page_size);
+  int exp_result;
+
+  memset (s1, 'a', page_size);
+  memset (s2, 'a', page_size);
+
+  s1[(page_size / CHARBYTES) - 1] = (CHAR) 0;
+  s2[(page_size / CHARBYTES) - 1] = (CHAR) 0;
+
+  /* Iterate over a size that is just below where we expect the bug to
+     trigger up to the size we expect will trigger the bug e.g. [99-128].
+     Likewise iterate the start of two strings between 30 and 31 bytes
+     away from the boundary to simulate alignment changes.  */
+  for (size_t s = 99; s <= size; s++)
+    for (size_t s1a = 30; s1a < 32; s1a++)
+      for (size_t s2a = 30; s2a < 32; s2a++)
+	{
+	  size_t align1 = (page_size / CHARBYTES - s) - s1a;
+	  size_t align2 = (page_size / CHARBYTES - s) - s2a;
+	  CHAR *s1p = s1 + align1;
+	  CHAR *s2p = s2 + align2;
+	  len = (page_size / CHARBYTES) - 1 - align1;
+	  exp_result = SIMPLE_STRCMP (s1p, s2p);
+	  do_one_test_page_boundary (json_ctx, s1p, s2p, align1, align2,
+				     len, exp_result);
+	}
+}
+
 int
 test_main (void)
 {
@@ -197,6 +251,8 @@ test_main (void)
       do_test (&json_ctx, 2 * CHARBYTES * i, CHARBYTES * i, 8 << i, LARGECHAR, -1);
     }
 
+  do_test_page_boundary (&json_ctx);
+
   json_array_end (&json_ctx);
   json_attr_object_end (&json_ctx);
   json_attr_object_end (&json_ctx);