[gcc/devel/omp/gcc-11] graphite: Accept loops without data references

[gcc/devel/omp/gcc-11] graphite: Accept loops without data references

[Frederik Harwath]

https://gcc.gnu.org/g:7bc13103c3ef408a1811a4d2ea935b03b6745451

commit 7bc13103c3ef408a1811a4d2ea935b03b6745451
Author: Frederik Harwath <frederik@codesourcery.com>
Date:   Tue Nov 16 16:22:29 2021 +0100

    graphite: Accept loops without data references
    
    It seems that the check that rejects loops without data references is
    only included to avoid handling non-profitable loops.  Including those
    loops in Graphite's analysis enables more consistent diagnostic
    messages in OpenACC "kernels" code and does not introduce any
    testsuite regressions.  If executing Graphite on loops without
    data references leads to noticeable compile time slow-downs for
    non-OpenACC users of Graphite, the check can be re-introduced but
    restricted to non-OpenACC functions.
    
    gcc/ChangeLog:
    
            * graphite-scop-detection.c (scop_detection::harmful_loop_in_region):
            Remove check for loops without data references.

Diff:
---
 gcc/graphite-scop-detection.c | 13 -------------
 1 file changed, 13 deletions(-)

diff --git a/gcc/graphite-scop-detection.c b/gcc/graphite-scop-detection.c
index 99e906a5d12..9311a0e42a5 100644
--- a/gcc/graphite-scop-detection.c
+++ b/gcc/graphite-scop-detection.c
@@ -851,19 +851,6 @@ scop_detection::harmful_loop_in_region (sese_l scop) const
 	  return true;
 	}
 
-      /* Check if all loop nests have at least one data reference.
-	 ???  This check is expensive and loops premature at this point.
-	 If important to retain we can pre-compute this for all innermost
-	 loops and reject those when we build a SESE region for a loop
-	 during SESE discovery.  */
-      if (! loop->inner
-	  && ! loop_nest_has_data_refs (loop))
-	{
-	  DEBUG_PRINT (dp << "[scop-detection-fail] loop_" << loop->num
-		       << " does not have any data reference.\n");
-	  return true;
-	}
-
       DEBUG_PRINT (dp << "[scop-detection] loop_" << loop->num << " is harmless.\n");
     }