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

1 files changed, 16 insertions, 6 deletions

diff --git a/gcc/sese.c b/gcc/sese.c
index aa19c68..797dea5 100644
--- a/gcc/sese.c
+++ b/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);
 }