fix invalid bounds on array refs

While enabling graphite in -O3 we found a Fortran testcase that fails
because the max of the type domain is -1.  We used to add that as a constraint
to the elements accessed by the array, leading to a unfeasible constraint:
0 <= i <= -1.  Having that constraint, drops the data reference as that says
that there are no elements accessed in the array.

	* graphite-dependences.c (scop_get_reads): Add extra dumps.
	(scop_get_must_writes): Same.
	(scop_get_may_writes): Same.
	(compute_deps): Same.
	* graphite-sese-to-poly.c (bounds_are_valid): New.
	(pdr_add_data_dimensions): Call bounds_are_valid.

	* gfortran.dg/graphite/run-id-3.f90: New.

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

From-SVN: r231191

5 files changed, 129 insertions, 45 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index a3e68b9..a3d9854 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,6 +1,16 @@
 2015-12-02  Aditya Kumar  <aditya.k7@samsung.com>
 	    Sebastian Pop  <s.pop@samsung.com>
 
+	* graphite-dependences.c (scop_get_reads): Add extra dumps.
+	(scop_get_must_writes): Same.
+	(scop_get_may_writes): Same.
+	(compute_deps): Same.
+	* graphite-sese-to-poly.c (bounds_are_valid): New.
+	(pdr_add_data_dimensions): Call bounds_are_valid.
+
+2015-12-02  Aditya Kumar  <aditya.k7@samsung.com>
+	    Sebastian Pop  <s.pop@samsung.com>
+
 	* common.opt (flag_loop_optimize_isl): Renamed flag_loop_nest_optimize.
 	* graphite-poly.c (apply_poly_transforms): Same.
 	* graphite.c (gate_graphite_transforms): Same.
diff --git a/gcc/graphite-dependences.c b/gcc/graphite-dependences.c
index fcc771b..bb81ae3 100644
--- a/gcc/graphite-dependences.c
+++ b/gcc/graphite-dependences.c
@@ -87,7 +87,11 @@ scop_get_reads (scop_p scop, vec<poly_bb_p> pbbs)
     {
       FOR_EACH_VEC_ELT (PBB_DRS (pbb), j, pdr)
 	if (pdr_read_p (pdr))
-	  res = isl_union_map_add_map (res, add_pdr_constraints (pdr, pbb));
+	  {
+	    if (dump_file)
+	      print_pdr (dump_file, pdr);
+	    res = isl_union_map_add_map (res, add_pdr_constraints (pdr, pbb));
+	  }
     }
 
   return res;
@@ -108,7 +112,11 @@ scop_get_must_writes (scop_p scop, vec<poly_bb_p> pbbs)
     {
       FOR_EACH_VEC_ELT (PBB_DRS (pbb), j, pdr)
 	if (pdr_write_p (pdr))
-	  res = isl_union_map_add_map (res, add_pdr_constraints (pdr, pbb));
+	  {
+	    if (dump_file)
+	      print_pdr (dump_file, pdr);
+	    res = isl_union_map_add_map (res, add_pdr_constraints (pdr, pbb));
+	  }
     }
 
   return res;
@@ -129,7 +137,12 @@ scop_get_may_writes (scop_p scop, vec<poly_bb_p> pbbs)
     {
       FOR_EACH_VEC_ELT (PBB_DRS (pbb), j, pdr)
 	if (pdr_may_write_p (pdr))
-	  res = isl_union_map_add_map (res, add_pdr_constraints (pdr, pbb));
+	  {
+	    if (dump_file)
+	      print_pdr (dump_file, pdr);
+
+	    res = isl_union_map_add_map (res, add_pdr_constraints (pdr, pbb));
+	  }
     }
 
   return res;
@@ -313,6 +326,36 @@ compute_deps (scop_p scop, vec<poly_bb_p> pbbs,
   isl_union_map *empty = isl_union_map_empty (space);
   isl_union_map *original = scop_get_original_schedule (scop, pbbs);
 
+  if (dump_file)
+    {
+      fprintf (dump_file, "\n--- Documentation for datarefs dump: ---\n");
+      fprintf (dump_file, "Statements on the iteration domain are mapped to"
+	       " array references.\n");
+      fprintf (dump_file, "  To read the following data references:\n\n");
+      fprintf (dump_file, "  S_5[i0] -> [106] : i0 >= 0 and i0 <= 3\n");
+      fprintf (dump_file, "  S_8[i0] -> [1, i0] : i0 >= 0 and i0 <= 3\n\n");
+
+      fprintf (dump_file, "  S_5[i0] is the dynamic instance of statement"
+	       " bb_5 in a loop that accesses all iterations 0 <= i0 <= 3.\n");
+      fprintf (dump_file, "  [1, i0] is a 'memref' with alias set 1"
+	       " and first subscript access i0.\n");
+      fprintf (dump_file, "  [106] is a 'scalar reference' which is the sum of"
+	       " SSA_NAME_VERSION 6"
+	       " and --param graphite-max-arrays-per-scop=100\n");
+      fprintf (dump_file, "-----------------------\n\n");
+
+      fprintf (dump_file, "data references (\n");
+      fprintf (dump_file, "  reads: ");
+      print_isl_union_map (dump_file, reads);
+      fprintf (dump_file, "  must_writes: ");
+      print_isl_union_map (dump_file, must_writes);
+      fprintf (dump_file, "  may_writes: ");
+      print_isl_union_map (dump_file, may_writes);
+      fprintf (dump_file, "  all_writes: ");
+      print_isl_union_map (dump_file, all_writes);
+      fprintf (dump_file, ")\n");
+    }
+
   isl_union_map_compute_flow (isl_union_map_copy (reads),
 			      isl_union_map_copy (must_writes),
 			      isl_union_map_copy (may_writes),
diff --git a/gcc/graphite-sese-to-poly.c b/gcc/graphite-sese-to-poly.c
index 7ef01fb..887c212 100644
--- a/gcc/graphite-sese-to-poly.c
+++ b/gcc/graphite-sese-to-poly.c
@@ -922,6 +922,33 @@ pdr_add_memory_accesses (isl_map *acc, dr_info &dri)
   return acc;
 }
 
+/* Return true when the LOW and HIGH bounds of an array reference REF are valid
+   to extract constraints on accessed elements of the array.  Returning false is
+   the conservative answer.  */
+
+static bool
+bounds_are_valid (tree ref, tree low, tree high)
+{
+  if (!high)
+    return false;
+
+  if (!tree_fits_shwi_p (low)
+      || !tree_fits_shwi_p (high))
+    return false;
+
+  /* 1-element arrays at end of structures may extend over
+     their declared size.  */
+  if (array_at_struct_end_p (ref)
+      && operand_equal_p (low, high, 0))
+    return false;
+
+  /* Fortran has some arrays where high bound is -1 and low is 0.  */
+  if (integer_onep (fold_build2 (LT_EXPR, boolean_type_node, high, low)))
+    return false;
+
+  return true;
+}
+
 /* Add constrains representing the size of the accessed data to the
    ACCESSES polyhedron.  ACCESSP_NB_DIMS is the dimension of the
    ACCESSES polyhedron, DOM_NB_DIMS is the dimension of the iteration
@@ -942,48 +969,35 @@ pdr_add_data_dimensions (isl_set *subscript_sizes, scop_p scop,
       tree low = array_ref_low_bound (ref);
       tree high = array_ref_up_bound (ref);
 
-      /* XXX The PPL code dealt separately with
-         subscript - low >= 0 and high - subscript >= 0 in case one of
-	 the two bounds isn't known.  Do the same here?  */
-
-      if (tree_fits_shwi_p (low)
-	  && high
-	  && tree_fits_shwi_p (high)
-	  /* 1-element arrays at end of structures may extend over
-	     their declared size.  */
-	  && !(array_at_struct_end_p (ref)
-	       && operand_equal_p (low, high, 0)))
-	{
-	  isl_id *id;
-	  isl_aff *aff;
-	  isl_set *univ, *lbs, *ubs;
-	  isl_pw_aff *index;
-	  isl_set *valid;
-	  isl_space *space = isl_set_get_space (subscript_sizes);
-	  isl_pw_aff *lb = extract_affine_int (low, isl_space_copy (space));
-	  isl_pw_aff *ub = extract_affine_int (high, isl_space_copy (space));
-
-	  /* high >= 0 */
-	  valid = isl_pw_aff_nonneg_set (isl_pw_aff_copy (ub));
-	  valid = isl_set_project_out (valid, isl_dim_set, 0,
-				       isl_set_dim (valid, isl_dim_set));
-	  scop->param_context = isl_set_intersect (scop->param_context, valid);
-
-	  aff = isl_aff_zero_on_domain (isl_local_space_from_space (space));
-	  aff = isl_aff_add_coefficient_si (aff, isl_dim_in, i + 1, 1);
-	  univ = isl_set_universe (isl_space_domain (isl_aff_get_space (aff)));
-	  index = isl_pw_aff_alloc (univ, aff);
-
-	  id = isl_set_get_tuple_id (subscript_sizes);
-	  lb = isl_pw_aff_set_tuple_id (lb, isl_dim_in, isl_id_copy (id));
-	  ub = isl_pw_aff_set_tuple_id (ub, isl_dim_in, id);
-
-	  /* low <= sub_i <= high */
-	  lbs = isl_pw_aff_ge_set (isl_pw_aff_copy (index), lb);
-	  ubs = isl_pw_aff_le_set (index, ub);
-	  subscript_sizes = isl_set_intersect (subscript_sizes, lbs);
-	  subscript_sizes = isl_set_intersect (subscript_sizes, ubs);
-	}
+      if (!bounds_are_valid (ref, low, high))
+	continue;
+
+      isl_space *space = isl_set_get_space (subscript_sizes);
+      isl_pw_aff *lb = extract_affine_int (low, isl_space_copy (space));
+      isl_pw_aff *ub = extract_affine_int (high, isl_space_copy (space));
+
+      /* high >= 0 */
+      isl_set *valid = isl_pw_aff_nonneg_set (isl_pw_aff_copy (ub));
+      valid = isl_set_project_out (valid, isl_dim_set, 0,
+				   isl_set_dim (valid, isl_dim_set));
+      scop->param_context = isl_set_intersect (scop->param_context, valid);
+
+      isl_aff *aff
+	= isl_aff_zero_on_domain (isl_local_space_from_space (space));
+      aff = isl_aff_add_coefficient_si (aff, isl_dim_in, i + 1, 1);
+      isl_set *univ
+	= isl_set_universe (isl_space_domain (isl_aff_get_space (aff)));
+      isl_pw_aff *index = isl_pw_aff_alloc (univ, aff);
+
+      isl_id *id = isl_set_get_tuple_id (subscript_sizes);
+      lb = isl_pw_aff_set_tuple_id (lb, isl_dim_in, isl_id_copy (id));
+      ub = isl_pw_aff_set_tuple_id (ub, isl_dim_in, id);
+
+      /* low <= sub_i <= high */
+      isl_set *lbs = isl_pw_aff_ge_set (isl_pw_aff_copy (index), lb);
+      isl_set *ubs = isl_pw_aff_le_set (index, ub);
+      subscript_sizes = isl_set_intersect (subscript_sizes, lbs);
+      subscript_sizes = isl_set_intersect (subscript_sizes, ubs);
     }
 
   return subscript_sizes;
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index e867353..edbed47 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2015-12-02  Aditya Kumar  <aditya.k7@samsung.com>
+	    Sebastian Pop  <s.pop@samsung.com>
+
+	* gfortran.dg/graphite/run-id-3.f90: New.
+
 2015-12-02  David Sherwood  <david.sherwood@arm.com>
 
         * gcc.target/aarch64/fmaxmin.c: New test.
diff --git a/gcc/testsuite/gfortran.dg/graphite/run-id-3.f90 b/gcc/testsuite/gfortran.dg/graphite/run-id-3.f90
new file mode 100644
index 0000000..54139ef
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/graphite/run-id-3.f90
@@ -0,0 +1,12 @@
+! { dg-do run }
+! { dg-options "-ffrontend-optimize -floop-nest-optimize" }
+! PR 56872 - wrong front-end optimization with a single constructor.
+! Original bug report by Rich Townsend.
+  integer :: k
+  real :: s
+  integer :: m
+  s = 2.0
+  m = 4
+  res = SUM([(s**(REAL(k-1)/REAL(m-1)),k=1,m)])
+  if (abs(res - 5.84732246) > 1e-6) call abort
+  end