Re: cprop fix for PR78626

[Jeff Law <law at redhat dot com>]

On 12/14/2016 08:46 AM, Bernd Schmidt wrote:
> On 12/12/2016 03:21 PM, Bernd Schmidt wrote:
> > On 12/10/2016 08:58 PM, Segher Boessenkool wrote:
> > > On Thu, Dec 08, 2016 at 01:21:04PM +0100, Bernd Schmidt wrote:
> > > > This is another case where an optimization turns a trap_if
> > > > unconditional. We have to defer changing the CFG, since the rest of
> > > > cprop seems to blow up when we modify things while scanning.
> >
> > > The problem for PR78727 is that we also need to do this for insns that
> > > already are the last insn in the block:
> > >
> > > > +      while (!uncond_traps.is_empty ())
> > > > +    {
> > > > +      rtx_insn *insn = uncond_traps.pop ();
> > > > +      basic_block to_split = BLOCK_FOR_INSN (insn);
> > > > +      remove_edge (split_block (to_split, insn));
> > > > +      emit_barrier_after_bb (to_split);
> > > > +    }
> > >
> > > We need that barrier, and we also need the successor edges removed
> > > (which split_block+remove_edge does).
> > >
> > > (PR78727 works fine with just that BB_END test deleted).
> >
> > Ah, ok. In that case I'll probably also add a test to make sure this is
> > only done for insns that weren't an unconditional trap before.
> > Retesting...
>
> That would be this patch. Tested as before. The two new testcases seem
> to pass with a ppc cross (but I would appreciate if someone were to run
> full tests on ppc).
>
>
> Bernd
>
>
> cprop-v2.diff
>
>
> 	PR rtl-optimization/78626
> 	PR rtl-optimization/78727
> 	* cprop.c (one_cprop_pass): Collect unconditional traps in the middle
> 	of a block, and split such blocks after everything else is finished.
>
> 	PR rtl-optimization/78626
> 	PR rtl-optimization/78727
> 	* gcc.dg/torture/pr78626.c: New test.
> 	* gcc.dg/torture/pr78727.c: New test.
This is OK.  I also re-tested ppc64le-linux since it's been about 3 
weeks since this patch was submitted.

I went ahead and committed the patch since you're on PTO and it kills 
stuff on the regression hit list.

jeff