Do not try to optimize empty SCoPs.

llvm-svn: 229253
diff --git a/polly/lib/Transform/ScheduleOptimizer.cpp b/polly/lib/Transform/ScheduleOptimizer.cpp
index 3409f87..2fd51a6 100644
--- a/polly/lib/Transform/ScheduleOptimizer.cpp
+++ b/polly/lib/Transform/ScheduleOptimizer.cpp
@@ -473,6 +473,14 @@
 }
 
 bool IslScheduleOptimizer::runOnScop(Scop &S) {
+
+  // Skip empty SCoPs but still allow code generation as it will delete the
+  // loops present but not needed.
+  if (S.getSize() == 0) {
+    S.markAsOptimized();
+    return false;
+  }
+
   Dependences *D = &getAnalysis<Dependences>();
 
   if (!D->hasValidDependences())