re PR fortran/65819 (overzealous checking in gfc_check_dependency for identical=true)

2019-07-25  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/65819
	* dependency.h (gfc_dep_resovler): Add optional argument identical.
	* dependency.c (gfc_check_dependency): Do not alway return 1 if
	the symbol is the same. Pass on identical to gfc_dep_resolver.
	(gfc_check_element_vs_element): Whitespace fix.
	(gfc_dep_resolver): Adjust comment for function.  If identical is
	true, return 1 if any overlap has been found.

2019-07-25  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/65819
	* gfortran.dg/dependency_54.f90: New test.

From-SVN: r273807

1 files changed, 25 insertions, 13 deletions

diff --git a/gcc/fortran/dependency.c b/gcc/fortran/dependency.c
index be330e2..da4a37c 100644
--- a/gcc/fortran/dependency.c
+++ b/gcc/fortran/dependency.c
@@ -1351,13 +1351,10 @@ gfc_check_dependency (gfc_expr *expr1, gfc_expr *expr2, bool identical)
 	  return 0;
 	}
 
-      if (identical)
-	return 1;
-
       /* Identical and disjoint ranges return 0,
 	 overlapping ranges return 1.  */
       if (expr1->ref && expr2->ref)
-	return gfc_dep_resolver (expr1->ref, expr2->ref, NULL);
+	return gfc_dep_resolver (expr1->ref, expr2->ref, NULL, identical);
 
       return 1;
 
@@ -1884,6 +1881,7 @@ gfc_check_element_vs_element (gfc_ref *lref, gfc_ref *rref, int n)
 
   if (i > -2)
     return GFC_DEP_NODEP;
+
   return GFC_DEP_EQUAL;
 }
 
@@ -2084,13 +2082,15 @@ ref_same_as_full_array (gfc_ref *full_ref, gfc_ref *ref)
 
 /* Finds if two array references are overlapping or not.
    Return value
-   	2 : array references are overlapping but reversal of one or
+	2 : array references are overlapping but reversal of one or
 	    more dimensions will clear the dependency.
-   	1 : array references are overlapping.
-   	0 : array references are identical or not overlapping.  */
+	1 : array references are overlapping, or identical is true and
+	    there is some kind of overlap.
+	0 : array references are identical or not overlapping.  */
 
 int
-gfc_dep_resolver (gfc_ref *lref, gfc_ref *rref, gfc_reverse *reverse)
+gfc_dep_resolver (gfc_ref *lref, gfc_ref *rref, gfc_reverse *reverse,
+		  bool identical)
 {
   int n;
   int m;
@@ -2124,11 +2124,15 @@ gfc_dep_resolver (gfc_ref *lref, gfc_ref *rref, gfc_reverse *reverse)
 
 	case REF_ARRAY:
 
+	  /* For now, treat all coarrays as dangerous.  */
+	  if (lref->u.ar.codimen || rref->u.ar.codimen)
+	    return 1;
+
 	  if (ref_same_as_full_array (lref, rref))
-	    return 0;
+	    return identical;
 
 	  if (ref_same_as_full_array (rref, lref))
-	    return 0;
+	    return identical;
 
 	  if (lref->u.ar.dimen != rref->u.ar.dimen)
 	    {
@@ -2180,6 +2184,8 @@ gfc_dep_resolver (gfc_ref *lref, gfc_ref *rref, gfc_reverse *reverse)
 		  gcc_assert (rref->u.ar.dimen_type[n] == DIMEN_ELEMENT
 			      && lref->u.ar.dimen_type[n] == DIMEN_ELEMENT);
 		  this_dep = gfc_check_element_vs_element (rref, lref, n);
+		  if (identical && this_dep == GFC_DEP_EQUAL)
+		    this_dep = GFC_DEP_OVERLAP;
 		}
 
 	      /* If any dimension doesn't overlap, we have no dependency.  */
@@ -2240,6 +2246,9 @@ gfc_dep_resolver (gfc_ref *lref, gfc_ref *rref, gfc_reverse *reverse)
 		 know the worst one.*/
 
 	    update_fin_dep:
+	      if (identical && this_dep == GFC_DEP_EQUAL)
+		this_dep = GFC_DEP_OVERLAP;
+
 	      if (this_dep > fin_dep)
 		fin_dep = this_dep;
 	    }
@@ -2253,7 +2262,7 @@ gfc_dep_resolver (gfc_ref *lref, gfc_ref *rref, gfc_reverse *reverse)
 
 	  /* Exactly matching and forward overlapping ranges don't cause a
 	     dependency.  */
-	  if (fin_dep < GFC_DEP_BACKWARD)
+	  if (fin_dep < GFC_DEP_BACKWARD && !identical)
 	    return 0;
 
 	  /* Keep checking.  We only have a dependency if
@@ -2267,11 +2276,14 @@ gfc_dep_resolver (gfc_ref *lref, gfc_ref *rref, gfc_reverse *reverse)
       rref = rref->next;
     }
 
+  /* Assume the worst if we nest to different depths.  */
+  if (lref || rref)
+    return 1;
+
   /* If we haven't seen any array refs then something went wrong.  */
   gcc_assert (fin_dep != GFC_DEP_ERROR);
 
-  /* Assume the worst if we nest to different depths.  */
-  if (lref || rref)
+  if (identical && fin_dep != GFC_DEP_NODEP)
     return 1;
 
   return fin_dep == GFC_DEP_OVERLAP;