[OpenMPOpt] Assume indirect call always changes ICV

[weiwang]

Summary

When checking call sites, give special handling to indirect call, as the
callee may be unknown and can lead to nullptr dereference later. Assume
conservatively that the ICV always changes in such case.

[lebedev.ri]

Test missing

[weiwang]

Add test case for indirect call. Without the fix, the test will crash.

[sstefan1]

LGTM, thanks!

llvm/lib/Transforms/IPO/OpenMPOpt.cpp

Optional<Value *> getValueForCall(Attributor &A, const Instruction *I,
     if (!CB)
       return None;
 
     auto &OMPInfoCache = static_cast<OMPInformationCache &>(A.getInfoCache());
     auto &GetterRFI = OMPInfoCache.RFIs[OMPInfoCache.ICVs[ICV].Getter];
     auto &SetterRFI = OMPInfoCache.RFIs[OMPInfoCache.ICVs[ICV].Setter];
     Function *CalledFunction = CB->getCalledFunction();
 
+    // Indirect call, assume ICV changes.
+    if (CalledFunction == nullptr)
+      return nullptr;
     if (CalledFunction == GetterRFI.Declaration)
       return None;
     if (CalledFunction == SetterRFI.Declaration) {
       if (ICVReplacementValuesMap[ICV].count(I))
         return ICVReplacementValuesMap[ICV].lookup(I);
 
       return nullptr;
     }