On Fri, Feb 28, 2014 at 2:09 AM, Richard Biener <richard.guent...@gmail.com> wrote: > On Fri, Feb 28, 2014 at 10:09 AM, Richard Biener > <richard.guent...@gmail.com> wrote: >> On Fri, Feb 28, 2014 at 1:52 AM, H.J. Lu <hjl.to...@gmail.com> wrote: >>> On Mon, Feb 24, 2014 at 9:12 PM, bin.cheng <bin.ch...@arm.com> wrote: >>>> Hi, >>>> This patch is to fix regression reported in PR60280 by removing forward >>>> loop >>>> headers/latches in cfg cleanup if possible. Several tests are broken by >>>> this change since cfg cleanup is shared by all optimizers. Some tests has >>>> already been fixed by recent patches, I went through and fixed the others. >>>> One case needs to be clarified is "gcc.dg/tree-prof/update-loopch.c". When >>>> GCC removing a basic block, it checks profile information by calling >>>> check_bb_profile after redirecting incoming edges of the bb. This >>>> certainly >>>> results in warnings about invalid profile information and causes the case >>>> to >>>> fail. I will send a patch to skip checking profile information for a >>>> removing basic block in stage 1 if it sounds reasonable. For now I just >>>> twisted the case itself. >>>> >>>> Bootstrap and tested on x86_64 and arm_a15. >>>> >>>> Is it OK? >>>> >>>> >>>> 2014-02-25 Bin Cheng <bin.ch...@arm.com> >>>> >>>> PR target/60280 >>>> * tree-cfgcleanup.c (tree_forwarder_block_p): Protect loop >>>> preheaders and latches only if requested. Fix latch if it >>>> is removed. >>>> * tree-ssa-dom.c (tree_ssa_dominator_optimize): Set >>>> LOOPS_HAVE_PREHEADERS. >>>> >>> >>> This change: >>> >>> if (dest->loop_father->header == dest) >>> - return false; >>> + { >>> + if (loops_state_satisfies_p (LOOPS_HAVE_PREHEADERS) >>> + && bb->loop_father->header != dest) >>> + return false; >>> + >>> + if (loops_state_satisfies_p (LOOPS_HAVE_SIMPLE_LATCHES) >>> + && bb->loop_father->header == dest) >>> + return false; >>> + } >>> } >>> >>> miscompiled 435.gromacs in SPEC CPU 2006 on x32 with >>> >>> -O3 -funroll-loops -ffast-math -fwhole-program -flto=jobserver >>> -fuse-linker-plugin >>> >>> This patch changes loops without LOOPS_HAVE_PREHEADERS >>> nor LOOPS_HAVE_SIMPLE_LATCHES from returning false to returning >>> true. I don't have a small testcase. But this patch: >>> >>> diff --git a/gcc/tree-cfgcleanup.c b/gcc/tree-cfgcleanup.c >>> index b5c384b..2ba673c 100644 >>> --- a/gcc/tree-cfgcleanup.c >>> +++ b/gcc/tree-cfgcleanup.c >>> @@ -323,6 +323,10 @@ tree_forwarder_block_p (basic_block bb, bool >>> phi_wanted) >>> if (loops_state_satisfies_p (LOOPS_HAVE_SIMPLE_LATCHES) >>> && bb->loop_father->header == dest) >>> return false; >>> + >>> + if (!loops_state_satisfies_p (LOOPS_HAVE_PREHEADERS) >>> + && !loops_state_satisfies_p (LOOPS_HAVE_SIMPLE_LATCHES)) >>> + return false; >>> } >>> } >>> >>> fixes the regression. Does it make any senses? >> >> I think the preheader test isn't fully correct (bb may be in an inner loop >> for example). So a more conservative variant would be >> >> Index: gcc/tree-cfgcleanup.c >> =================================================================== >> --- gcc/tree-cfgcleanup.c (revision 208169) >> +++ gcc/tree-cfgcleanup.c (working copy) >> @@ -316,13 +316,13 @@ tree_forwarder_block_p (basic_block bb, >> /* Protect loop preheaders and latches if requested. */ >> if (dest->loop_father->header == dest) >> { >> - if (loops_state_satisfies_p (LOOPS_HAVE_PREHEADERS) >> - && bb->loop_father->header != dest) >> - return false; >> - >> - if (loops_state_satisfies_p (LOOPS_HAVE_SIMPLE_LATCHES) >> - && bb->loop_father->header == dest) >> - return false; >> + if (bb->loop_father == dest->loop_father) >> + return !loops_state_satisfies_p (LOOPS_HAVE_SIMPLE_LATCHES); >> + else if (bb->loop_father == loop_outer (dest->loop_father)) >> + return !loops_state_satisfies_p (LOOPS_HAVE_PREHEADERS); >> + /* Always preserve other edges into loop headers that are >> + not simple latches or preheaders. */ >> + return false; >> } >> } >> >> that makes sure we can properly update loop information. It's also >> a more conservative change at this point which should still successfully >> remove simple latches and preheaders created by loop discovery. > > I think the patch makes sense anyway and thus I'll install it once it > passed bootstrap / regtesting. > > Another fix that may make sense is to restrict it to > !loops_state_satisfies_p (LOOPS_NEED_FIXUP), though cfgcleanup > itself can end up setting that ... which we eventually should fix if it > still happens. That is, check if > > Index: gcc/tree-cfgcleanup.c > =================================================================== > --- gcc/tree-cfgcleanup.c (revision 208169) > +++ gcc/tree-cfgcleanup.c (working copy) > > @@ -729,8 +729,9 @@ cleanup_tree_cfg_noloop (void) > > timevar_pop (TV_TREE_CLEANUP_CFG); > > - if (changed && current_loops) > - loops_state_set (LOOPS_NEED_FIXUP); > + if (changed && current_loops > + && !loops_state_satisfies_p (LOOPS_NEED_FIXUP)) > + verify_loop_structure (); > > return changed; > } > > trips anywhere (and apply fixes). That's of course not appropriate at > this stage. > >> Does it fix 435.gromacs?
I tried revision 208222 and it doesn't fix 435.gromacs. > I can't see the failure on our testers (x86_64, i?86, with/without LTO). How > can I reproduce it? > It only happens with -mx32 -O3 -funroll-loops -ffast-math -fwhole-program -flto=jobserver -fuse-linker-plugin The failure is Running 435.gromacs ref peak lto default *** Miscompare of gromacs.out; for details see /export/project/git/gcc-regression/spec/2006/spec/benchspec/CPU2006/435.grom acs/run/run_peak_ref_lto.0000/gromacs.out.mis cat /export/project/git/gcc-regression/spec/2006/spec/benchspec/CPU2006/435.gromacs/run/run_peak_ref_lto.0000/gromacs.out.mis 0002: 3.07684e+02 3.03594e+02 It is very sensitive to loop optimization. -- H.J.