Re: [PATCH][6/n] Merge from match-and-simplify, make forwprop fold all stmts

[Jeff Law <law@redhat.com>]

On 10/24/14 07:16, Richard Biener wrote:
>
> This patch makes GIMPLE forwprop fold all statements, following
> single-use SSA edges only (as suggested by Jeff and certainly
> how this will regress the least until we replace manual
> simplification code that does not restrict itself this way).
>
> forwprop is run up to 4 times at the moment (once only for -Og,
> not at all for -O0), which still seems reasonable.  IMHO the
> forwprop pass immediately after inlining is somewhat superfluous,
> it was added there just for its ADDR_EXPR propagation.  We should
> eventually split this pass into two.
>
> Note that just folding what we propagated into (like the SSA
> propagators do during substitute-and-fold phase) will miss
> cases where we propagate into a stmt feeding the one we could
> simplify.  Unless we always fold all single-use (and their use)
> stmts we have to fold everything from time to time.  Changing
> how / when we fold stuff is certainly sth to look after with
> fold_stmt now being able to follow SSA edges.
>
> Bootstrapped on x86_64-unknown-linux-gnu, testing still in progress.
>
>  From earlier testing I remember I need to adjust a few testcases
> that don't expect the early folding - notably two strlenopt cases
> (previously XFAILed but then PASSed again).
>
> I also expect to massage the single-use heuristic as I get to
> merging the patterns I added for the various forwprop manual
> pattern matchings to trunk (a lot of them do not restrict themselves
> this way).
>
> Does this otherwise look ok?
>
> Thanks,
> Richard.
>
> 2014-10-24  Richard Biener  <rguenther@suse.de>
>
> 	* tree-ssa-forwprop.c: Include tree-cfgcleanup.h and tree-into-ssa.h.
> 	(lattice): New global.
> 	(fwprop_ssa_val): New function.
> 	(fold_all_stmts): Likewise.
> 	(pass_forwprop::execute): Finally fold all stmts.
Seems reasonable.  After all, we can iterate on the single-use heuristic.

jeff