[tree-ssa] RFC: Making control flow more explicit

[Zdenek Dvorak]

Hello,

> >From an optimization point of view I see very little value in keeping
> LOOP_EXPR and SWITCH_EXPRs, for instance.  But without evidence to the
> contrary, I had thought that as a first cut we should probably start by
> dropping them in a post-gimplification pass.  We can always remove them
> from GIMPLE altogether if we find no other use for them.  I don't think
> we'll find them useful, though.
> 
> Zdenek, how much work would it be to clean up your patches that deal
> with LOOP_EXPRs, COND_EXPRs and SWITCH_EXPRs?  I'm particularly
> interested in LOOP_EXPRs.  For SWITCH_EXPRs, I think going to a
> multi-way branch is probably the easiest solution.  That means using the
> label vector collected in the SWITCH_EXPR and converting those into real
> LABEL_DECLs.

I already have a separate patch for loop_exprs, I will send it soon.
Concerning COND and SWITCH exprs, I will have to check how much work
will there be with cleanups, but I don't think it should be somehow
extremely hard.

Zdenek