[patch] Fix PR43464: update loop closed SSA form once copy prop is done

[Sebastian Pop]

On Tue, Mar 23, 2010 at 22:40, Kenneth Zadeck
<Kenneth.Zadeck@naturalbridge.com> wrote:
> Let me try to bring some perspective back into this discussion,
> because it is clear that this is getting out of hand.
>
> There are two solutions that must be considered: a short term one and
> a long term one.
>
> At this stage, a rewrite of a pass of the compiler is not acceptable,
> so calling that rewrite_into_closed_loop_ssa form in a place
> immediately after the pass that messed it up is the correct short term
> solution.  And it is purely Richard's call as to how careful that
> patch needs to be about checking if things get messed up.
>
> However, I agree with Steven that this is a very poor long term
> solution that should be strongly avoided.  Unswitching needs to be
> more careful about the damage that it does to the representation.

Ok, I stand corrected.

I will work on getting all the patches necessary to maintain the
LCSSA form during the LNO.  As this will take time and could
introduce new errors, I will propose these changes only for 4.6.

Sebastian