Do not require memset elimination in explicit_bzero test

Some targets fail to apply dead store elimination to the
memset call in setup_ordinary_clear.  Before this commit,
this causes the test case to fail.  Instead, the test case
now logs lack of memset elimination as an informational
message.

diff --git a/ChangeLog b/ChangeLog
index 3e6a39fe52ae18de1508ff0829ea9b7cffcee31b..8cdcae68fbb28cd94fb22e56570e4f033ad039e5 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2016-12-20  Florian Weimer  <fweimer@redhat.com>
+
+       Do not require memset elimination in explicit_bzero test.
+       * string/tst-xbzero-opt.c (prepare_test_buffer): Force inlining.
+       (enum test_expectation): Add NO_EXPECTATIONS.
+       (subtests): NO_EXPECTATIONS for ordinary clear.
+       (check_test_buffer): Handle NO_EXPECTATIONS.
+       * string/Makefile (CFLAGS-tst-xbzero-opt.c): Compile with -O3.
+
 2016-12-20  Joseph Myers  <joseph@codesourcery.com>
 
        * math/bits/mathcalls.h [__GLIBC_USE (IEC_60559_BFP_EXT)]

diff --git a/string/Makefile b/string/Makefile
index 9a8b46d1bf7a14d26b2e50901fd82c74a056dbe4..081627734d63aafeebe8fb6b6d435ed1d5a3cff0 100644 (file)
--- a/string/Makefile
+++ b/string/Makefile
@@ -71,6 +71,7 @@ CFLAGS-tst-strlen.c = -fno-builtin
 CFLAGS-stratcliff.c = -fno-builtin
 CFLAGS-test-ffs.c = -fno-builtin
 CFLAGS-tst-inlcall.c = -fno-builtin
+CFLAGS-tst-xbzero-opt.c = -O3
 
 ifeq ($(run-built-tests),yes)
 $(objpfx)tst-svc-cmp.out: tst-svc.expect $(objpfx)tst-svc.out

diff --git a/string/tst-xbzero-opt.c b/string/tst-xbzero-opt.c
index 312857e056a9fbd49655da48946abc427e9cfb59..3fcaf283d209905f98920e66431e9255b8623d75 100644 (file)
--- a/string/tst-xbzero-opt.c
+++ b/string/tst-xbzero-opt.c
@@ -88,19 +88,19 @@ static const unsigned char test_pattern[16] =
    between preparing it and letting it go out of scope, and we expect
    to find it.  This confirms that the test buffer does get filled in
    and we can find it from the stack buffer.  In the "ordinary_clear"
-   case, we clear it using memset, and we expect to find it.  This
-   confirms that the compiler can optimize out block clears in this
-   context; if it can't, the real test might be succeeding for the
-   wrong reason.  Finally, the "explicit_clear" case uses
-   explicit_bzero and expects _not_ to find the test buffer, which is
-   the real test.  */
+   case, we clear it using memset.  Depending on the target, the
+   compiler may not be able to apply dead store elimination to the
+   memset call, so the test does not fail if the memset is not
+   eliminated.  Finally, the "explicit_clear" case uses explicit_bzero
+   and expects _not_ to find the test buffer, which is the real
+   test.  */
 
 static ucontext_t uc_main, uc_co;
 
 /* 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.  */
-static void
+static inline __attribute__  ((always_inline)) void
 prepare_test_buffer (unsigned char *buf)
 {
   for (unsigned int i = 0; i < PATTERN_REPS; i++)
@@ -133,7 +133,10 @@ setup_explicit_clear (void)
   explicit_bzero (buf, TEST_BUFFER_SIZE);
 }
 
-enum test_expectation { EXPECT_NONE, EXPECT_SOME, EXPECT_ALL };
+enum test_expectation
+  {
+    EXPECT_NONE, EXPECT_SOME, EXPECT_ALL, NO_EXPECTATIONS
+  };
 struct subtest
 {
   void (*setup_subtest) (void);
@@ -145,7 +148,9 @@ static const struct subtest *cur_subtest;
 static const struct subtest subtests[] =
 {
   { setup_no_clear,       "no clear",       EXPECT_SOME },
-  { setup_ordinary_clear, "ordinary clear", EXPECT_SOME },
+  /* The memset may happen or not, depending on compiler
+     optimizations.  */
+  { setup_ordinary_clear, "ordinary clear", NO_EXPECTATIONS },
   { setup_explicit_clear, "explicit clear", EXPECT_NONE },
   { 0,                    0,                -1          }
 };
@@ -225,6 +230,11 @@ check_test_buffer (enum test_expectation expected,
        }
       break;
 
+    case NO_EXPECTATIONS:
+      printf ("INFO: %s/%s: found %d patterns%s\n", label, stage, cnt,
+             cnt == 0 ? " (memset not eliminated)" : "");
+      break;
+
     default:
       printf ("ERROR: %s/%s: invalid value for 'expected' = %d\n",
              label, stage, (int)expected);