On Thu, 6 Nov 2014, pins...@gmail.com wrote: > > > > > > On Nov 6, 2014, at 11:24 PM, Richard Biener <rguent...@suse.de> wrote: > > > >> On November 7, 2014 5:03:19 AM CET, Andrew Pinski <pins...@gmail.com> > >> wrote: > >> On Thu, Nov 6, 2014 at 2:40 AM, Richard Biener <rguent...@suse.de> > >> wrote: > >>> On Thu, 6 Nov 2014, Richard Biener wrote: > >>> > >>>>> On Wed, 5 Nov 2014, Andrew Pinski wrote: > >>>>> > >>>>> Hi, > >>>>> I was trying to hook up tree-ssa-phiopt to match-and-simplify > >> using > >>>>> either gimple_build (or rather using gimple_simplify depending on > >> if > >>>>> we want to produce cond_expr for conditional move). I ran into a > >>>>> problem. > >>>>> With the pattern below: > >>>>> /* a ? 0 : 1 -> a if 0 and 1 are integral types. */ > >>>>> (simplify > >>>>> (cond_expr @0 integer_zerop integer_onep) > >>>>> (if (INTEGRAL_TYPE_P (type)) > >>>>> (convert @0))) > >>>> > >>>> Ok, so you are capturing a GENERIC expr here but nothing knows that. > >>>> It would work if you'd do (ugh) > >>>> > >>>> (for op (lt le eq ne ge gt) > >>>> (simplify > >>>> (cond_expr (op @0 @1) integer_zerop integer_onep) > >>>> (if (INTEGRAL_TYPE_P (type)) > >>>> (convert (op @0 @1))))) > >>>> (simplify > >>>> (cond_expr SSA_NAME@0 integer_zerop integer_onep) > >>>> (if (INTEGRAL_TYPE_P (type)) > >>>> (convert @0)))) > >>>> > >>>> as a workaround. To make your version work will require (quite) > >>>> some special-casing in the code generator or maybe the resimplify > >>>> helper. Let me see if I can cook up a "simple" fix. > >>> > >>> Sth like below (for the real fix this has to be replicated in > >>> all gimple_resimplifyN functions). I'm missing a testcase > >>> where the pattern would apply (and not be already folded by fold), > >>> so I didn't check if it actually works. > >> > >> You do need to check if seq is NULL though as gimple_build depends on > >> seq not being NULL. But otherwise yes this works for me. > >> > >>> > >>> Bah, of course we should fix COND_EXPRs to not embed a GENERIC > >>> expr... > >> > >> Yes totally agree. For my changes to tree-ssa-phiopt, I no longer > >> embed it. Though we need to change loop ifconvert still. > > > > Istr expansion or code quality does not like us to cse the condition of two > > cobd_exprs either. After all I had a patch set at some point doing that > > conversion (though as well for gimple_conds). > > I thought I changed that when I did the expansion of cond_expr into > conditional move. We need to something similar for cond_expr of jumps > too.
Well, SSA coalescing may make simple forwarding of the conditions impossible (and TER doesn't work for multiple uses anyway). That said, the most "interesting" issues for cond_exprs of jumps was PRE eliminating partial redundant conditions (thus it noted jump threading opportunities without actually performing the block duplication). Generated code for such PREd conditions was ... "interesting" :/ Richard.
