a scalar depending on vdefs in the current region is not invariant

When a scalar is defined in function of an array reference in the current scop,
it does variate.  Graphite cannot represent the condition in scop-11.c, as a[*]
variates in the current region, and it is not an affine condition:

  for (j = 0; j <= 20; j++)
    a[j] = b + i;

  if (a[12] == 23)
    b = 3;
  else
    b = 1;

  for (j = 0; j <= 20; j++)
    a[j] = b + i;

	* graphite-scop-detection.c (parameter_index_in_region): Update call to
	invariant_in_sese_p_rec.
	* graphite-sese-to-poly.c (extract_affine): Same.
	* sese.c (invariant_in_sese_p_rec): Pass in an extra parameter has_vdefs.
	(scalar_evolution_in_region): Return chrec_dont_know when the scalar variable
	depends on virtual definitions in the current region.
	* sese.h (invariant_in_sese_p_rec): Update declaration.

testsuite/
	* gcc.dg/graphite/scop-11.c: Update pattern.

Co-Authored-By: Sebastian Pop <s.pop@samsung.com>

From-SVN: r229151

gcc/ChangeLog

@@ -1,3 +1,14 @@
+2015-10-21  Aditya Kumar  <aditya.k7@samsung.com>
+	    Sebastian Pop  <s.pop@samsung.com>
+
+	* graphite-scop-detection.c (parameter_index_in_region): Update call to
+	invariant_in_sese_p_rec.
+	* graphite-sese-to-poly.c (extract_affine): Same.
+	* sese.c (invariant_in_sese_p_rec): Pass in an extra parameter has_vdefs.
+	(scalar_evolution_in_region): Return chrec_dont_know when the scalar variable
+	depends on virtual definitions in the current region.
+	* sese.h (invariant_in_sese_p_rec): Update declaration.
+
 2015-10-21  Aditya Kumar  <aditya.k7@samsung.com>
 	    Sebastian Pop  <s.pop@samsung.com>
 

gcc/graphite-scop-detection.c

@@ -1521,7 +1521,7 @@ parameter_index_in_region (tree name, sese_info_p region)
   if (TREE_CODE (TREE_TYPE (name)) != INTEGER_TYPE)
     return -1;
 
-  if (!invariant_in_sese_p_rec (name, region->region))
+  if (!invariant_in_sese_p_rec (name, region->region, NULL))
     return -1;
 
   i = parameter_index_in_region_1 (name, region);

gcc/graphite-sese-to-poly.c

@@ -540,7 +540,7 @@ extract_affine (scop_p s, tree e, __isl_take isl_space *space)
 
     case SSA_NAME:
       gcc_assert (-1 != parameter_index_in_region_1 (e, s->scop_info)
-		  || !invariant_in_sese_p_rec (e, s->scop_info->region));
+		  || !invariant_in_sese_p_rec (e, s->scop_info->region, NULL));
       res = extract_affine_name (s, e, space);
       break;
 

gcc/sese.c

@@ -787,10 +787,11 @@ set_ifsese_condition (ifsese if_region, tree condition)
 }
 
 /* Return true when T is defined outside REGION or when no definitions are
-   variant in REGION.  */
+   variant in REGION.  When HAS_VDEFS is a valid pointer, sets HAS_VDEFS to true
+   when T depends on memory that may change in REGION.  */
 
 bool
-invariant_in_sese_p_rec (tree t, sese_l &region)
+invariant_in_sese_p_rec (tree t, sese_l &region, bool *has_vdefs)
 {
   ssa_op_iter iter;
   use_operand_p use_p;
@@ -805,11 +806,15 @@ invariant_in_sese_p_rec (tree t, sese_l &region)
 
   /* VDEF is variant when it is in the region.  */
   if (gimple_vdef (stmt))
-    return false;
+    {
+      if (has_vdefs)
+	*has_vdefs = true;
+      return false;
+    }
 
   /* A VUSE may or may not be variant following the VDEFs.  */
   if (tree vuse = gimple_vuse (stmt))
-    return invariant_in_sese_p_rec (vuse, region);
+    return invariant_in_sese_p_rec (vuse, region, has_vdefs);
 
   FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE)
     {
@@ -818,7 +823,7 @@ invariant_in_sese_p_rec (tree t, sese_l &region)
       if (!defined_in_sese_p (use, region))
 	continue;
 
-      if (!invariant_in_sese_p_rec (use, region))
+      if (!invariant_in_sese_p_rec (use, region, has_vdefs))
 	return false;
     }
 
@@ -856,8 +861,13 @@ scalar_evolution_in_region (sese_l &region, loop_p loop, tree t)
       return t;
     }
 
-  if (invariant_in_sese_p_rec (t, region))
+  bool has_vdefs = false;
+  if (invariant_in_sese_p_rec (t, region, &has_vdefs))
     return t;
 
+  /* T variates in REGION.  */
+  if (has_vdefs)
+    return chrec_dont_know;
+
   return instantiate_scev (before, loop, t);
 }

gcc/sese.h

@@ -84,7 +84,7 @@ extern edge copy_bb_and_scalar_dependences (basic_block, sese_info_p, edge,
 					    vec<tree> , bool *);
 extern struct loop *outermost_loop_in_sese (sese_l &, basic_block);
 extern tree scalar_evolution_in_region (sese_l &, loop_p, tree);
-extern bool invariant_in_sese_p_rec (tree, sese_l &);
+extern bool invariant_in_sese_p_rec (tree, sese_l &, bool *);
 
 /* Check that SESE contains LOOP.  */
 

gcc/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2015-10-21  Aditya Kumar  <aditya.k7@samsung.com>
+	    Sebastian Pop  <s.pop@samsung.com>
+
+	* gcc.dg/graphite/scop-11.c: Update pattern.
+
 2015-10-11  Jan Hubicka  <hubicka@ucw.cz>
 
 	PR ipa/67056

gcc/testsuite/gcc.dg/graphite/scop-11.c

@@ -19,4 +19,4 @@ int toto (int i, int b)
   return a[b];
 }
 
-/* { dg-final { scan-tree-dump-times "number of SCoPs: 1" 1 "graphite"} } */
+/* { dg-final { scan-tree-dump-times "number of SCoPs: 0" 1 "graphite"} } */