Segfault from @atomic operation on typed field (miscompilation?)

[adienes]

this MWE segfaults

mutable struct Atomic
    @atomic x::Int
end

function add_one!()
    @atomic (Atomic(0).x) += 1
end

add_one!() # segfaults

but note it works fine if either the ::Int is removed, or if the Atomic(0) is constructed before passing in

mutable struct Atomic
    @atomic x::Int
end

function add_one!(a)
    @atomic (a.x) += 1
end

add_one!(Atomic(0)) # works

bisected to #51720

[vtjnash]

This is a bug in our AllocOptPass pass

frame #3: 0x0000000100febad0 libjulia-codegen.1.12.0.dylib`(anonymous namespace)::Optimizer::optimizeAll() [inlined] (anonymous namespace)::Optimizer::moveToStack(llvm::CallInst*, unsigned long, bool, llvm::AllocFnKind)::$_3::operator()(this=<unavailable>, user=0x00006000008ff810) const at llvm-alloc-opt.cpp:805:13 [opt]
   802 	            push_frame(gep, new_gep);
   803 	        }
   804 	        else {
-> 805 	            abort();
   806 	        }
   807 	    };
   808 	

(lldb) p user->dump()
  %7 = cmpxchg ptr addrspace(11) %4, i64 %5, i64 %6 seq_cst monotonic, align 8, !dbg !37, !tbaa !40, !alias.scope !35, !noalias !36