x86: Add string/memory function tests in RTM region

At function exit, AVX optimized string/memory functions have VZEROUPPER
which triggers RTM abort.   When such functions are called inside a
transactionally executing RTM region, RTM abort causes severe performance
degradation.  Add tests to verify that string/memory functions won't
cause RTM abort in RTM region.

1 files changed, 72 insertions, 0 deletions

diff --git a/sysdeps/x86/tst-string-rtm.h b/sysdeps/x86/tst-string-rtm.h
new file mode 100644
index 0000000000..d2470afa1e
--- /dev/null
+++ b/sysdeps/x86/tst-string-rtm.h
@@ -0,0 +1,72 @@
+/* Test string function in a transactionally executing RTM region.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <string.h>
+#include <x86intrin.h>
+#include <sys/platform/x86.h>
+#include <support/check.h>
+#include <support/test-driver.h>
+
+static int
+do_test_1 (const char *name, unsigned int loop, int (*prepare) (void),
+	   int (*function) (void))
+{
+  if (!CPU_FEATURE_USABLE (RTM))
+    return EXIT_UNSUPPORTED;
+
+  int status = prepare ();
+  if (status != EXIT_SUCCESS)
+    return status;
+
+  unsigned int i;
+  unsigned int naborts = 0;
+  unsigned int failed = 0;
+  for (i = 0; i < loop; i++)
+    {
+      failed |= function ();
+      if (_xbegin() == _XBEGIN_STARTED)
+	{
+	  failed |= function ();
+	  _xend();
+	}
+      else
+	{
+	  failed |= function ();
+	  ++naborts;
+	}
+    }
+
+  if (failed)
+    FAIL_EXIT1 ("%s() failed", name);
+
+  if (naborts)
+    {
+      /* NB: Low single digit (<= 5%) noise-level aborts are normal for
+	 TSX.  */
+      double rate = 100 * ((double) naborts) / ((double) loop);
+      if (rate > 5)
+	FAIL_EXIT1 ("TSX abort rate: %.2f%% (%d out of %d)",
+		    rate, naborts, loop);
+    }
+
+  return EXIT_SUCCESS;
+}
+
+static int do_test (void);
+
+#include <support/test-driver.c>