DeadObjectElimination: ignore begin_access and end_access instructions

Don't let access instructions prevent eliminating dead allocations

#66496

Author: eeckstein

lib/SILOptimizer/Transforms/DeadObjectElimination.cpp

@@ -280,6 +280,9 @@ static bool canZapInstruction(SILInstruction *Inst, bool acceptRefCountInsts,
   if (isa<InitExistentialAddrInst>(Inst))
     return true;
 
+  if (isa<BeginAccessInst>(Inst) || isa<EndAccessInst>(Inst))
+    return true;
+
   // If Inst does not read or write to memory, have side effects, and is not a
   // terminator, we can zap it.
   if (!Inst->mayHaveSideEffects() && !Inst->mayReadFromMemory() &&

test/SILOptimizer/dead_alloc_elim.sil

@@ -127,7 +127,9 @@ sil @store_to_trivial_property : $@convention(thin) (Int) -> () {
 bb0(%0 : $Int):
   %20 = alloc_ref [stack] $NontrivialDestructor
   %21 = ref_element_addr %20 : $NontrivialDestructor, #NontrivialDestructor.i
-  store %0 to %21 : $*Int
+  %22 = begin_access [modify] [dynamic] %21 : $*Int
+  store %0 to %22 : $*Int
+  end_access %22 : $*Int
   set_deallocating %20 : $NontrivialDestructor
   dealloc_ref %20 : $NontrivialDestructor
   dealloc_stack_ref %20 : $NontrivialDestructor