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

[H.J. Lu]

On Wed, Nov 5, 2014 at 12:25 AM, Zhenqiang Chen <zhenqiang.chen@arm.com> wrote:
> The patch leads to big regression for float operators on target without hard
> fpu support due to register shuffle.
>
> Please refer https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63743 for more
> detail.
>
> Thanks!
> -Zhenqiang
>
>> -----Original Message-----
>> From: gcc-patches-owner@gcc.gnu.org [mailto:gcc-patches-
>> owner@gcc.gnu.org] On Behalf Of Jeff Law
>> Sent: Saturday, October 25, 2014 1:48 AM
>> To: Richard Biener; gcc-patches@gcc.gnu.org
>> Cc: Jakub Jelinek
>> Subject: Re: [PATCH][6/n] Merge from match-and-simplify, make forwprop
>> fold all stmts
>>
>> 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.
>>
>

This also caused:

//gcc.gnu.org/bugzilla/show_bug.cgi?id=64511



-- 
H.J.