[MemorySSA] Don't create new memory accesses for dbg intrinsics in MemorySSA

[ChuanqiXu]

Summary

After we landed https://reviews.llvm.org/D127383, the compiler may crash at: https://github.com/llvm/llvm-project/blob/051738b08cf5e39fd274dd379147d1c19e2b5b20/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp#L687-L691.

This is because the dbg intrinsics are readnone originally and the MemorySSA would refuse to create a new memory access at https://github.com/llvm/llvm-project/blob/051738b08cf5e39fd274dd379147d1c19e2b5b20/llvm/lib/Analysis/MemorySSA.cpp#L1830-L1831

But after D127383, it wouldn't be true for the dbg intrinsics in presplit coroutine. So here is the crash.

[ChuanqiXu]

Add unit tests.

[ChuanqiXu]

llvm/lib/Analysis/MemorySSA.cpp

1780–1782

Given these comments, the following changes look reasonable.

[asbirlea]

LGTM.

[ChuanqiXu]

We prefer https://reviews.llvm.org/D135550

llvm/lib/Analysis/MemorySSA.cpp

 }
 
 /// Helper function to create new memory accesses
 template <typename AliasAnalysisType>
 MemoryUseOrDef *MemorySSA::createNewAccess(Instruction *I,
                                            AliasAnalysisType *AAP,
                                            const MemoryUseOrDef *Template) {
   // The assume intrinsic has a control dependency which we model by claiming
   // that it writes arbitrarily. Debuginfo intrinsics may be considered
   // clobbers when we have a nonstandard AA pipeline. Ignore these fake memory
   // dependencies here.
   // FIXME: Replace this special casing with a more accurate modelling of
   // assume's control dependency.
   if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
     switch (II->getIntrinsicID()) {
     default:
       break;
     case Intrinsic::assume:
     case Intrinsic::experimental_noalias_scope_decl:
     case Intrinsic::pseudoprobe:
+    case Intrinsic::dbg_addr:
+    case Intrinsic::dbg_declare:
+    case Intrinsic::dbg_label:
+    case Intrinsic::dbg_value:
       return nullptr;
     }
   }
 
   // Using a nonstandard AA pipelines might leave us with unexpected modref
   // results for I, so add a check to not model instructions that may not read
   // from or write to memory. This is necessary for correctness.
   if (!I->mayReadFromMemory() && !I->mayWriteToMemory())