MEM flags and stack temps

[Richard Kenner]

    Yes!  With the second approach, it will then be straightforward to get
    rid of the huge number of dead stores we get on C++ code (currently
    once an object is assigned to the stack and we write it, the compiler
    is incapable of seeing that the value is not needed).  All (ok, big
    "all") we need to do is extend dead code elimination to work on stack
    slots where addresses are not taken (currently the dead code
    eliminator in dce.c believes that all writes to memory are necessary
    under all conditions).

The problem is timing: you also want to be able to do CSE and loop
optimizations on the addresss of temporaries that aren't eliminated if they
are outside the addressable range of the machine.