Dependences: Only create flat StmtSchedule in presence of reductions

Without reductions we do not need a flat union_map schedule describing
the computation we want to perform, but can work purely on the schedule
tree. This reduces the dependence computation and scheduling time from 33ms
to 25ms. Another 30% reduction.

llvm-svn: 280558

polly/lib/Analysis/DependenceInfo.cpp

@@ -173,7 +173,7 @@ static void collectInfo(Scop &S, isl_union_map **Read, isl_union_map **Write,
         *Write = isl_union_map_add_map(*Write, accdom);
     }
 
-    if (Level == Dependences::AL_Statement)
+    if (!ReductionBaseValues.empty() && Level == Dependences::AL_Statement)
       *StmtSchedule = isl_union_map_add_map(*StmtSchedule, Stmt.getSchedule());
   }