testsuite: Reduce gcc.dg/torture/inline-mem-cpy-1.c by 11 for simulators

The test inline-mem-cpy-1.c takes 16 minutes at -O0 for the mmix
simulator on a 3.5 year old laptop and thus always times out, despite
the x 2 timeout (i.e. 10 minutes), and times out at all optimization
levels.  For the included file (when run as gcc.dg/memcmp-1.c), the
execution time on the same host is 9 minutes 54 seconds, so just
within 10 minutes timeout limit.  Seems pragmatically best to reduce
the torture-test by a factor of about 10, but there's no obvious small
set of entities to scale down to get the intended effect, and
splitting up the test into several tests seem a bit too intrusive.

Instead, introduce pseudo-random machinery to skip all but each
RUN_FRACTION:th iteration, defaulting to no change when RUN_FRACTION
isn't defined.  Use 11 for RUN_FRACTION, assuming this prime will lead
to even distribution within nested iterations with loops looking like
(0, 1) : (0, 1).  Do this only for the main loop in
test_driver_memcmp; the "outermost" two levels of iterations.

With this, execution time for -O0 as above is down to 1 minute 32
seconds.

	* gcc.dg/torture/inline-mem-cpy-1.c: Pass -DRUN_FRACTION=11
	when testing in a simulator.
	* gcc.dg/memcmp-1.c [RUN_FRACTION]: Add machinery to run only
	for each RUN_FRACTION:th iteration.
	(main): Call initialize_skip_iteration_count.
	(test_driver_memcmp): Check SKIP_ITERATION for each iteration.

2 files changed, 36 insertions, 0 deletions

diff --git a/gcc/testsuite/gcc.dg/memcmp-1.c b/gcc/testsuite/gcc.dg/memcmp-1.c
index ea837ca..13ef5b3 100644
--- a/gcc/testsuite/gcc.dg/memcmp-1.c
+++ b/gcc/testsuite/gcc.dg/memcmp-1.c
@@ -34,6 +34,36 @@ int lib_strncmp(const char *a, const char *b, size_t n)
 
 #define MAX_SZ 600
 
+/* A means to run only a fraction of the tests, beginning at a random
+   count.  */
+#ifdef RUN_FRACTION
+
+#define SKIP_ITERATION skip_iteration ()
+static unsigned int iteration_count;
+
+static _Bool
+skip_iteration (void)
+{
+  _Bool run = ++iteration_count == RUN_FRACTION;
+
+  if (run)
+    iteration_count = 0;
+
+  return !run;
+}
+
+static void
+initialize_skip_iteration_count ()
+{
+  srand (2024);
+  iteration_count = (unsigned int) (rand ()) % RUN_FRACTION;
+}
+
+#else
+#define SKIP_ITERATION 0
+#define initialize_skip_iteration_count()
+#endif
+
 #define DEF_RS(ALIGN)                                                      \
 static void test_memcmp_runtime_size_ ## ALIGN (const char *str1, 	   \
 						const char *str2,	   \
@@ -110,6 +140,8 @@ static void test_driver_memcmp (void (test_memcmp)(const char *, const char *, i
   int i,j,l;
   for(l=0;l<sz;l++) {
     for(i=0;i<NRAND/sz;i++) {
+      if (SKIP_ITERATION)
+	continue;
       for(j=0;j<l;j++) {
 	buf1[j] = rand() & 0xff;
 	buf2[j] = buf1[j];
@@ -128,6 +160,8 @@ static void test_driver_memcmp (void (test_memcmp)(const char *, const char *, i
   for(diff_pos = ((test_sz>TZONE)?(test_sz-TZONE):0); diff_pos < test_sz+TZONE; diff_pos++)
     for(zero_pos = ((test_sz>TZONE)?(test_sz-TZONE):0); zero_pos < test_sz+TZONE; zero_pos++)
       {
+	if (SKIP_ITERATION)
+	  continue;
 	memset(buf1, 'A', 2*test_sz);
 	memset(buf2, 'A', 2*test_sz);
 	buf2[diff_pos] = 'B';
@@ -490,6 +524,7 @@ DEF_TEST(49,1)
 int
 main(int argc, char **argv)
 {
+  initialize_skip_iteration_count ();
 #ifdef TEST_ALL
     RUN_TEST(1,1)
     RUN_TEST(1,2)
diff --git a/gcc/testsuite/gcc.dg/torture/inline-mem-cpy-1.c b/gcc/testsuite/gcc.dg/torture/inline-mem-cpy-1.c
index f495255..f075234 100644
--- a/gcc/testsuite/gcc.dg/torture/inline-mem-cpy-1.c
+++ b/gcc/testsuite/gcc.dg/torture/inline-mem-cpy-1.c
@@ -1,5 +1,6 @@
 /* { dg-do run } */
 /* { dg-options "-finline-stringops=memcpy -save-temps -g0 -fno-lto" } */
+/* { dg-additional-options "-DRUN_FRACTION=11" { target simulator } } */
 /* { dg-timeout-factor 2 } */
 
 #include "../memcmp-1.c"