[PATCH 2/2] [graphite] a scalar depending on vdefs in the current region is not invariant

[Sebastian Pop]

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.
---
 gcc/graphite-scop-detection.c           |  2 +-
 gcc/graphite-sese-to-poly.c             |  2 +-
 gcc/sese.c                              | 22 ++++++++++++++++------
 gcc/sese.h                              |  2 +-
 gcc/testsuite/gcc.dg/graphite/scop-11.c |  2 +-
 5 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/gcc/graphite-scop-detection.c b/gcc/graphite-scop-detection.c
index f425f01..e39f5b4 100644
--- a/gcc/graphite-scop-detection.c
+++ b/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);
diff --git a/gcc/graphite-sese-to-poly.c b/gcc/graphite-sese-to-poly.c
index 261e67d..8971250 100644
--- a/gcc/graphite-sese-to-poly.c
+++ b/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->region)
-                 || !invariant_in_sese_p_rec (e, s->region->region));
+                 || !invariant_in_sese_p_rec (e, s->region->region, NULL));
       res = extract_affine_name (s, e, space);
       break;
 
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);
 }
diff --git a/gcc/sese.h b/gcc/sese.h
index d429d58..a428396 100644
--- a/gcc/sese.h
+++ b/gcc/sese.h
@@ -95,7 +95,7 @@ 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.  */
 
diff --git a/gcc/testsuite/gcc.dg/graphite/scop-11.c 
b/gcc/testsuite/gcc.dg/graphite/scop-11.c
index 801e54f..6362003 100644
--- a/gcc/testsuite/gcc.dg/graphite/scop-11.c
+++ b/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"} } */
-- 
1.9.1