ScheduleOpt: Do not crash on statements with empty iteration domains

Statements with an empty iteration domain may not have a schedule assigned by
the isl schedule optimizer. As Polly expects each statement to have a schedule,
we keep the old schedule for such statements.

This fixes http://llvm.org/PR15645`

Reported-by: Johannes Doerfert  <johannesdoerfert@gmx.de>
llvm-svn: 179233

diff --git a/polly/lib/ScheduleOptimizer.cpp b/polly/lib/ScheduleOptimizer.cpp
index 1063977..e37b759 100644 (file)
--- a/polly/lib/ScheduleOptimizer.cpp
+++ b/polly/lib/ScheduleOptimizer.cpp
@@ -537,8 +537,21 @@ bool IslScheduleOptimizer::runOnScop(Scop &S) {
     isl_union_map *StmtBand;
     StmtBand = isl_union_map_intersect_domain(isl_union_map_copy(ScheduleMap),
                                               isl_union_set_from_set(Domain));
-    isl_map *StmtSchedule;
+    isl_map *StmtSchedule = NULL;
     isl_union_map_foreach_map(StmtBand, getSingleMap, &StmtSchedule);
+
+    // Statements with an empty iteration domain may not have a schedule
+    // assigned by the isl schedule optimizer. As Polly expects each statement
+    // to have a schedule, we keep the old schedule for this statement. As
+    // there are zero iterations to execute, the content of the schedule does
+    // not matter.
+    //
+    // TODO: Consider removing such statements when constructing the scop.
+    if (!StmtSchedule) {
+      StmtSchedule = Stmt->getScattering();
+      StmtSchedule = isl_map_set_tuple_id(StmtSchedule, isl_dim_out, NULL);
+    }
+
     Stmt->setScattering(StmtSchedule);
     isl_union_map_free(StmtBand);
   }

diff --git a/polly/test/ScheduleOptimizer/2013-04-11-Empty-Domain-two.ll b/polly/test/ScheduleOptimizer/2013-04-11-Empty-Domain-two.ll
new file mode 100644 (file)
index 0000000..15d7dc6
--- /dev/null
+++ b/polly/test/ScheduleOptimizer/2013-04-11-Empty-Domain-two.ll
@@ -0,0 +1,24 @@
+; RUN: opt %loadPolly -polly-opt-isl -S %s
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+; Check that we handle statements with an empty iteration domain correctly.
+
+define void @f() {
+entry:
+  %A = alloca double
+  br label %for
+
+for:
+  %indvar = phi i32 [ %indvar.next, %for.inc ], [ 0, %entry ]
+  %exitcond = icmp ne i32 %indvar, -1
+  br i1 %exitcond, label %for.inc, label %return
+
+for.inc:
+  %indvar.next = add i32 %indvar, 1
+  store double 1.0, double* %A
+  br label %for
+
+return:
+  ret void
+}