[AbstractAttributor] Fix two issues in folding __kmpc_is_spmd_exec_mode

[tianshilei1992]

Summary

This patch fixed two issues found when folding __kmpc_is_spmd_exec_mode:

1. When the reaching kernels are empty, it should not fold to generic mode.
2. When creating AA for the caller when updating information, the dependency should be required.

[tianshilei1992]

check SimplifiedValue when empty reaching kernels

[ye-luo]

I checked both the reproducer and miniQMC. The reported bug https://bugs.llvm.org/show_bug.cgi?id=51124 can be fixed by this patch.

llvm/lib/Transforms/IPO/OpenMPOpt.cpp

 private:
   /// Update info regarding reaching kernels.
   void updateReachingKernelEntries(Attributor &A) {
     auto PredCallSite = [&](AbstractCallSite ACS) {
       Function *Caller = ACS.getInstruction()->getFunction();
 
       assert(Caller && "Caller is nullptr");
 
-      auto &CAA =
-          A.getOrCreateAAFor<AAKernelInfo>(IRPosition::function(*Caller));
+      auto &CAA = A.getOrCreateAAFor<AAKernelInfo>(
+          IRPosition::function(*Caller), this, DepClassTy::REQUIRED);
       if (CAA.ReachingKernelEntries.isValidState()) {
         ReachingKernelEntries ^= CAA.ReachingKernelEntries;
         return true;
       }
 
       // We lost track of the caller of the associated function, any kernel
       // could reach now.
       ReachingKernelEntries.indicatePessimisticFixpoint();
ChangeStatus foldIsSPMDExecMode(Attributor &A) {
 
     auto &Ctx = getAnchorValue().getContext();
     if (KnownSPMDCount || AssumedSPMDCount) {
       assert(KnownNonSPMDCount == 0 && AssumedNonSPMDCount == 0 &&
              "Expected only SPMD kernels!");
       // All reaching kernels are in SPMD mode. Update all function calls to
       // __kmpc_is_spmd_exec_mode to 1.
       SimplifiedValue = ConstantInt::get(Type::getInt8Ty(Ctx), true);
-    } else {
+    } else if (KnownNonSPMDCount || AssumedNonSPMDCount) {
       assert(KnownSPMDCount == 0 && AssumedSPMDCount == 0 &&
              "Expected only non-SPMD kernels!");
       // All reaching kernels are in non-SPMD mode. Update all function
       // calls to __kmpc_is_spmd_exec_mode to 0.
       SimplifiedValue = ConstantInt::get(Type::getInt8Ty(Ctx), false);
+    } else {
+      // We have empty reaching kernels, therefore we cannot tell if the
+      // associated call site can be folded. At this moment, SimplifiedValue
+      // must be none.
+      assert(!SimplifiedValue.hasValue() && "SimplifiedValue should be none");
     }
 
     return SimplifiedValue == SimplifiedValueBefore ? ChangeStatus::UNCHANGED
                                                     : ChangeStatus::CHANGED;
   }
 
   /// An optional value the associated value is assumed to fold to. That is, we
   /// assume the associated value (which is a call) can be replaced by this