The reason this is true is that an assign is an instruction in PMO parlance that
must destroy the value stored into memory at that location previously. So PMO
would need to be taught to ensure that said destroy is promoted. Consider the
following example:
%0 = alloc_stack $Foo
store %1 to [init] %0 : $*Foo
store %2 to [assign] %0 : $*Foo
destroy_addr %0 : $*Foo
dealloc_stack %0 : $*Foo
If PMO were to try to eliminate the alloc_stack as PMO is written today, one
would have:
destroy_value %2 : $Foo
That is clearly wrong.
