[tree-ssa] COND_EXPR lowering preview

[Zdenek Dvorak]

Hello,

> > here is the patch; since it is just preview and I am lazy, it includes
> > some parts that should be separated, most imporatantly tree-ssa-dom fixes.
> > The patch bootstraps and passes regtesting.
> > 
> Please separate them.

of course; as I stated, this is not ment for review.

> > It disables control structures removal in dce; this also has to be
> > handled separately.
> > 
> What does this have to do with COND_EXPR lowering?

control structures removal as implemented currently relies on structured
COND_EXPRs, so something has to be done with it.

> > Some possibly useful cleanups were removed from
> > remove_useless_stmts_and_vars; this function is not suitable for
> > work over unstructured code.
> > 
> Again.  Please separate this.  It has little to do with COND_EXPR
> lowering.

It's just a removal of code that becomes useless when COND_EXPRs are
unstructured -- imho this has a lot to do with COND_EXPR lowering :-)

Zdenek