Re: Modifies vs. Replaces

[brender at gemevn dot zko dot dec dot com (Ron 603-884-2088)]

Michael Eager writes:
>So far, I've heard rumors of this complicated general case, or of 
>conjectured hypothetical optimizations which would make updating 
>the global location incorrect, but there have been no examples presented.  

The "hypothetical optimizations which would make updating the global
location incorrect" is just the possibility that the global location
may be used for some other purpose during that range of addresses where
the real value is only available elsewhere (eg in a register).

Jim and I have both indicated this is probably rare-but neither is
saying that it impossible to occur or unreasonable for a compiler
to employ (ie, it is not "bad code generation" to do this, of itself).

Because it is rare but possible, we prefer a DWARF specification that
does not precluding describing it if it does occur.

Perhaps by "no examples presented" you mean that no compilers have been
identified that actually employ this technique. It is true that I can't
point to one (not even my own Compaq compilers). Jim and others will
have to speak for themselves on that point...