GPGPU: Do not fail in case of arrays never accessed

If these arrays have never been accessed we failed to derive an upper bound
of the accesses and consequently a size for the outermost dimension. We
now explicitly check for empty access sets and then just use zero as size
for the outermost dimension.

llvm-svn: 281165

1 files changed, 21 insertions, 11 deletions

diff --git a/polly/lib/CodeGen/PPCGCodeGeneration.cpp b/polly/lib/CodeGen/PPCGCodeGeneration.cpp
index eac819d930b..66ffa730acc 100644
--- a/polly/lib/CodeGen/PPCGCodeGeneration.cpp
+++ b/polly/lib/CodeGen/PPCGCodeGeneration.cpp
@@ -1784,17 +1784,27 @@ public:
   /// @param Array The polly array from which to take the information.
   void setArrayBounds(gpu_array_info &PPCGArray, ScopArrayInfo *Array) {
     if (PPCGArray.n_index > 0) {
-      isl_set *Dom = isl_set_copy(PPCGArray.extent);
-      Dom = isl_set_project_out(Dom, isl_dim_set, 1, PPCGArray.n_index - 1);
-      isl_pw_aff *Bound = isl_set_dim_max(isl_set_copy(Dom), 0);
-      isl_set_free(Dom);
-      Dom = isl_pw_aff_domain(isl_pw_aff_copy(Bound));
-      isl_local_space *LS = isl_local_space_from_space(isl_set_get_space(Dom));
-      isl_aff *One = isl_aff_zero_on_domain(LS);
-      One = isl_aff_add_constant_si(One, 1);
-      Bound = isl_pw_aff_add(Bound, isl_pw_aff_alloc(Dom, One));
-      Bound = isl_pw_aff_gist(Bound, S->getContext());
-      PPCGArray.bound[0] = Bound;
+      if (isl_set_is_empty(PPCGArray.extent)) {
+        isl_set *Dom = isl_set_copy(PPCGArray.extent);
+        isl_local_space *LS = isl_local_space_from_space(
+            isl_space_params(isl_set_get_space(Dom)));
+        isl_set_free(Dom);
+        isl_aff *Zero = isl_aff_zero_on_domain(LS);
+        PPCGArray.bound[0] = isl_pw_aff_from_aff(Zero);
+      } else {
+        isl_set *Dom = isl_set_copy(PPCGArray.extent);
+        Dom = isl_set_project_out(Dom, isl_dim_set, 1, PPCGArray.n_index - 1);
+        isl_pw_aff *Bound = isl_set_dim_max(isl_set_copy(Dom), 0);
+        isl_set_free(Dom);
+        Dom = isl_pw_aff_domain(isl_pw_aff_copy(Bound));
+        isl_local_space *LS =
+            isl_local_space_from_space(isl_set_get_space(Dom));
+        isl_aff *One = isl_aff_zero_on_domain(LS);
+        One = isl_aff_add_constant_si(One, 1);
+        Bound = isl_pw_aff_add(Bound, isl_pw_aff_alloc(Dom, One));
+        Bound = isl_pw_aff_gist(Bound, S->getContext());
+        PPCGArray.bound[0] = Bound;
+      }
     }
 
     for (unsigned i = 1; i < PPCGArray.n_index; ++i) {