[MemorySSA +LICM CFHoist] Solve PR40317.

[asbirlea]

Summary

MemorySSA needs updating each time an instruction is moved.
LICM and control flow hoisting re-hoists instructions, thus needing another update when re-moving those instructions.
Pending cleanup: the MSSA update is duplicated, should be moved inside moveInstructionBefore.

[asbirlea]

Add test-case.

lib/Transforms/Scalar/LICM.cpp

for (Instruction *I : reverse(HoistedInstructions)) {
             assert(DT->dominates(Dominator, HoistPoint->getParent()) &&
                    "New hoist point expected to dominate old hoist point");
           HoistPoint = Dominator->getTerminator();
         }
         LLVM_DEBUG(dbgs() << "LICM rehoisting to "
                           << HoistPoint->getParent()->getName()
                           << ": " << *I << "\n");
         moveInstructionBefore(*I, *HoistPoint, *SafetyInfo);
+        if (MSSAU)
+          if (MemoryUseOrDef *OldMemAcc = cast_or_null<MemoryUseOrDef>(
+              MSSAU->getMemorySSA()->getMemoryAccess(I)))
+            MSSAU->moveToPlace(OldMemAcc, HoistPoint->getParent(), MemorySSA::End);
         HoistPoint = I;
         Changed = true;
       }
     }
   }
   if (MSSAU && VerifyMemorySSA)
     MSSAU->getMemorySSA()->verifyMemorySSA();