[OpenMP] Prevent Attributor from deleting functions in OpenMPOptCGSCC pass

[jhuber6]

Summary

This patch prevents the Attributor instances made in the CGSCC pass from
deleting functions. This prevents the attributor from changing the call
graph while OpenMPOpt is working with it.

[jdoerfert]

LG

[lebedev.ri]

Test missing?
Shouldn't the deletions be simply deferred until after?

[jhuber6]

In D102363#2755292, @lebedev.ri wrote:

Test missing?
Shouldn't the deletions be simply deferred until after?

I don't think we need any tests, this is just a preemptive measure to avoid some future bugs.

llvm/lib/Transforms/IPO/OpenMPOpt.cpp

PreservedAnalyses OpenMPOptCGSCCPass::run(LazyCallGraph::SCC &C,
   BumpPtrAllocator Allocator;
   CallGraphUpdater CGUpdater;
   CGUpdater.initialize(CG, C, AM, UR);
 
   SetVector<Function *> Functions(SCC.begin(), SCC.end());
   OMPInformationCache InfoCache(*(Functions.back()->getParent()), AG, Allocator,
                                 /*CGSCC*/ Functions, OMPInModule.getKernels());
 
-  Attributor A(Functions, InfoCache, CGUpdater);
+  Attributor A(Functions, InfoCache, CGUpdater, nullptr, false);
 
   OpenMPOpt OMPOpt(SCC, CGUpdater, OREGetter, InfoCache, A);
   bool Changed = OMPOpt.run(false);
   if (Changed)
     return PreservedAnalyses::none();
 
   return PreservedAnalyses::all();
 }
+
 namespace {
 
 struct OpenMPOptCGSCCLegacyPass : public CallGraphSCCPass {
   CallGraphUpdater CGUpdater;
   OpenMPInModule OMPInModule;
   static char ID;
 
   OpenMPOptCGSCCLegacyPass() : CallGraphSCCPass(ID) {
bool runOnSCC(CallGraphSCC &CGSCC) override {
 
     AnalysisGetter AG;
     SetVector<Function *> Functions(SCC.begin(), SCC.end());
     BumpPtrAllocator Allocator;
     OMPInformationCache InfoCache(
         *(Functions.back()->getParent()), AG, Allocator,
         /*CGSCC*/ Functions, OMPInModule.getKernels());
 
-    Attributor A(Functions, InfoCache, CGUpdater);
+    Attributor A(Functions, InfoCache, CGUpdater, nullptr, false);
 
     OpenMPOpt OMPOpt(SCC, CGUpdater, OREGetter, InfoCache, A);
     return OMPOpt.run(false);
   }
 
   bool doFinalization(CallGraph &CG) override { return CGUpdater.finalize(); }
 };