GNU C Library master sources branch master updated. glibc-2.27.9000-646-gc9dc4d5

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http://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=c9dc4d5117afea7283d5fd80c80be8cc09cde84d

commit c9dc4d5117afea7283d5fd80c80be8cc09cde84d
Author: Stefan Liebler <stli@linux.ibm.com>
Date:   Thu Jul 26 17:09:44 2018 +0200

    Fix string/tst-xbzero-opt if build with gcc head.
    
    On s390x, the test string/tst-xbzero-opt is failing if build with gcc head:
    FAIL: no clear/prepare: expected 32 got 0
    FAIL: no clear/test: expected some got 0
    FAIL: ordinary clear/prepare: expected 32 got 0
    INFO: ordinary clear/test: found 0 patterns (memset not eliminated)
    PASS: explicit clear/prepare: expected 32 got 32
    PASS: explicit clear/test: expected 0 got 0
    
    In setup_no_clear / setup_ordinary_clear, GCC is omitting the memcpy loop
    in prepare_test_buffer. Thus count_test_patterns does not find any of the
    test_pattern.
    
    This patch calls use_test_buffer in order to force the compiler to really copy
    the pattern to buf.
    
    ChangeLog:
    
    	* string/tst-xbzero-opt.c (use_test_buffer): New function.
    	(prepare_test_buffer): Call use_test_buffer as compiler barrier.

diff --git a/ChangeLog b/ChangeLog
index d88a798..3e25bd7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2018-07-26  Stefan Liebler  <stli@linux.ibm.com>
+
+	* string/tst-xbzero-opt.c (use_test_buffer): New function.
+	(prepare_test_buffer): Call use_test_buffer as compiler barrier.
+
 2018-07-26  Florian Weimer  <fweimer@redhat.com>
 
 	* htl/lockfile.c (flockfile, funlockfile, ftrylockfile): Use weak
diff --git a/string/tst-xbzero-opt.c b/string/tst-xbzero-opt.c
index aab4a7f..898345b 100644
--- a/string/tst-xbzero-opt.c
+++ b/string/tst-xbzero-opt.c
@@ -97,6 +97,17 @@ static const unsigned char test_pattern[16] =
 
 static ucontext_t uc_main, uc_co;
 
+static __attribute__ ((noinline, noclone)) int
+use_test_buffer (unsigned char *buf)
+{
+  unsigned int sum = 0;
+
+  for (unsigned int i = 0; i < PATTERN_REPS; i++)
+    sum += buf[i * PATTERN_SIZE];
+
+  return (sum == 2 * PATTERN_REPS) ? 0 : 1;
+}
+
 /* Always check the test buffer immediately after filling it; this
    makes externally visible side effects depend on the buffer existing
    and having been filled in.  */
@@ -116,6 +127,10 @@ prepare_test_buffer (unsigned char *buf)
 
   if (swapcontext (&uc_co, &uc_main))
     abort ();
+
+  /* Force the compiler to really copy the pattern to buf.  */
+  if (use_test_buffer (buf))
+    abort ();
 }
 
 static void

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog               |    5 +++++
 string/tst-xbzero-opt.c |   15 +++++++++++++++
 2 files changed, 20 insertions(+), 0 deletions(-)


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