[gcc r12-4338] Adjust testcase for O2 vectorization enabling

[gcc r12-4338] Adjust testcase for O2 vectorization enabling

[hongtao Liu]

https://gcc.gnu.org/g:d61ce6ab04ee98f1f64b54436bca96054cc62329

commit r12-4338-gd61ce6ab04ee98f1f64b54436bca96054cc62329
Author: liuhongt <hongtao.liu@intel.com>
Date:   Mon Oct 11 10:05:03 2021 +0800

    Adjust testcase for O2 vectorization enabling
    
    This issue was observed in rs6000 specific PR102658 as well.
    
    I've looked into it a bit, it's caused by the "conditional store replacement" which
    is originally disabled without vectorization as below code.
    
      /* If either vectorization or if-conversion is disabled then do
         not sink any stores.  */
      if (param_max_stores_to_sink == 0
          || (!flag_tree_loop_vectorize && !flag_tree_slp_vectorize)
          || !flag_tree_loop_if_convert)
        return false;
    
    The new change makes the innermost loop look like
    
    for (int c1 = 0; c1 <= 1499; c1 += 1) {
      if (c1 <= 500) {
         S_10(c0, c1);
      } else {
          S_9(c0, c1);
      }
      S_11(c0, c1);
    }
    
    and can not be splitted as:
    
    for (int c1 = 0; c1 <= 500; c1 += 1)
      S_10(c0, c1);
    
    for (int c1 = 501; c1 <= 1499; c1 += 1)
      S_9(c0, c1);
    
    So instead of disabling vectorization, could we just disable this cs replacement
    with parameter "--param max-stores-to-sink=0"?
    
    I tested this proposal on ppc64le, it should work as well.
    
    2021-10-11  Kewen Lin  <linkw@linux.ibm.com>
    
    libgomp/ChangeLog:
    
            * testsuite/libgomp.graphite/force-parallel-8.c: Add --param max-stores-to-sink=0.

Diff:
---
 libgomp/testsuite/libgomp.graphite/force-parallel-8.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libgomp/testsuite/libgomp.graphite/force-parallel-8.c b/libgomp/testsuite/libgomp.graphite/force-parallel-8.c
index f9e07039172..6868dd29147 100644
--- a/libgomp/testsuite/libgomp.graphite/force-parallel-8.c
+++ b/libgomp/testsuite/libgomp.graphite/force-parallel-8.c
@@ -1,4 +1,4 @@
-/* { dg-additional-options "-fdisable-tree-thread1 -fdisable-tree-vrp-thread1" } */
+/* { dg-additional-options "-fdisable-tree-thread1 -fdisable-tree-vrp-thread1 --param max-stores-to-sink=0" } */
 
 #define N 1500