https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103061
--- Comment #12 from Andrew Macleod <amacleod at redhat dot com> --- On 11/5/21 8:02 AM, aldyh at gcc dot gnu.org wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103061 > > --- Comment #7 from Aldy Hernandez <aldyh at gcc dot gnu.org> --- > Simplified version without the noise: > > <bb 35> [local count: 56063504182]: > _134 = M.10_120 + 1; > if (_71 <= _134) > goto <bb 19>; [11.00%] > else > goto <bb 41>; [89.00%] > > ... > ... > > <bb 41> [local count: 49896518755]: > > <bb 20> [local count: 56063503181]: > # lb_75 = PHI <_134(41), 1(18)> > _117 = mstep_49 + lb_75; > _118 = _117 + -1; > _119 = mstep_49 + _118; > M.10_120 = MIN_EXPR <_119, _71>; > if (lb_75 > M.10_120) > goto <bb 21>; [11.00%] > else > goto <bb 22>; [89.00%] > > If _134 can be assumed to be greater than M.10_120, then we can thread > 41->20->21. > I dont understand why? isnt m.10_120 killed in bb20? whats the basis for threading that? I dont see it layed out, the thread would be: <bb 35> [local count: 56063504182]: _134 = M.10_120 + 1; *relation _71 >_134 <bb 20> [local count: 56063503181]: lb_75 = _134 _117 = mstep_49 + lb_75; __117 = mstep_49 + _134 _118 = _117 + -1; _119 = mstep_49 + _118; mstep_49 + mstep_49 + _134 + -1 M.10_120 = MIN_EXPR <_119, _71>; MIN < ^that, _134> kill m.10_120 if (lb_75 > M.10_120) if (OLD-M.10_120 + 1 > m.10_120) goto <bb 21>; [11.00%] else goto <bb 22>; [89.00%] I dont see how you can thread to 21?
