Re: [patch] Decompose gimplify_expr

[Daniel Berlin <dberlin at dberlin dot org>]

> In any case, I don't intend to implement any complicated optimizations.
> I definitely will avoid any "special case handling";
> if the optimization is too complicated, it is hardly worth doing
> at the expansion time.  I will be considering only simple optimizations
> like unreachable code removal and constant propagation that have
> a good chance to be very useful and save significant amount of memory
> and compile time (especially on code that uses macros a lot).\

I will simply note that we have *already* run into issues because things
like "constant propagation" were added to cleanup_cfg.  (It ends up
causing us to need to update ssa in some cases that it doesn't do, and
shouldn't have to, since it's a fricking cfg cleanup pass)

There are always corner cases in simple optimizations that nobody thinks
about that bite us in the ass later.