[OpenMP] Fix some non-determinism causing test failures in reverse iterator builds

[mnadeem]

Summary

The tests custom_state_machines_remarks.ll and spmdization_remarks.ll fail with
reverse iterator builds due to non-determinism in the iteration order. This patch tries to fix it.

Change KernelSet from SmallPtrSet to SmallSetVector so that the order of
iteration of kernels in OpenMPOpt::registerAAs() is the same as the order of insertion.

llvm/include/llvm/Transforms/IPO/OpenMPOpt.h

 namespace llvm {
 
 namespace omp {
 
 /// Summary of a kernel (=entry point for target offloading).
 using Kernel = Function *;
 
 /// Set of kernels in the module
-using KernelSet = SmallPtrSet<Kernel, 4>;
+using KernelSet = SmallSetVector<Kernel, 4>;
 
 /// Helper to determine if \p M contains OpenMP.
 bool containsOpenMP(Module &M);
 
 /// Helper to determine if \p M is a OpenMP target offloading device module.
 bool isOpenMPDevice(Module &M);
 
 /// Get OpenMP device kernels in \p M.

llvm/lib/Transforms/IPO/OpenMPOpt.cpp

 
 struct AAICVTracker;
 
 /// OpenMP specific information. For now, stores RFIs and ICVs also needed for
 /// Attributor runs.
 struct OMPInformationCache : public InformationCache {
   OMPInformationCache(Module &M, AnalysisGetter &AG,
                       BumpPtrAllocator &Allocator, SetVector<Function *> &CGSCC,
-                      SmallPtrSetImpl<Kernel> &Kernels)
+                      KernelSet &Kernels)
       : InformationCache(M, AG, Allocator, &CGSCC), OMPBuilder(M),
         Kernels(Kernels) {
 
     OMPBuilder.initialize();
     initializeRuntimeFunctions();
     initializeInternalControlVars();
   }
 
#define OMP_RTL(_Enum, _Name, _IsVarArg, _ReturnType, ...)                     \
     }                                                                          \
   }
 #include "llvm/Frontend/OpenMP/OMPKinds.def"
 
     // TODO: We should attach the attributes defined in OMPKinds.def.
   }
 
   /// Collection of known kernels (\see Kernel) in the module.
-  SmallPtrSetImpl<Kernel> &Kernels;
+  KernelSet &Kernels;
 
   /// Collection of known OpenMP runtime functions..
   DenseSet<const Function *> RTLFunctions;
 };
 
 template <typename Ty, bool InsertInvalidates = true>
 struct BooleanStateWithSetVector : public BooleanState {
   bool contains(const Ty &Elem) const { return Set.contains(Elem); }