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Re: [PATCH, PR69068] Handle 3-arg phi in copy_bb_and_scalar_dependences
- From: Richard Biener <rguenther at suse dot de>
- To: Tom de Vries <Tom_deVries at mentor dot com>
- Cc: Sebastian Pop <sebpop at gmail dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Mon, 30 May 2016 12:56:45 +0200 (CEST)
- Subject: Re: [PATCH, PR69068] Handle 3-arg phi in copy_bb_and_scalar_dependences
- Authentication-results: sourceware.org; auth=none
- References: <574C09F9 dot 1050201 at mentor dot com> <alpine dot LSU dot 2 dot 11 dot 1605301142440 dot 1493 at t29 dot fhfr dot qr> <574C1766 dot 5090806 at mentor dot com>
On Mon, 30 May 2016, Tom de Vries wrote:
> On 30/05/16 11:46, Richard Biener wrote:
> > > This patch fixes the assert conservatively by aborting graphite code
> > > >generation when encountering a phi with more than two arguments in
> > > >copy_bb_and_scalar_dependences.
> > > >
> > > >Bootstrapped and reg-tested on x86_64.
> > > >
> > > >OK for trunk, 6 branch?
>
> > Did you check if simply returning false from bb_contains_loop_phi_nodes
> > instead of asserting works? The caller has a 'else' that is supposed
> > to handle condition PHIs. After all it already handles one predecessor
> > specially ... Thus
> >
> > if (EDGE_COUNT (bb->preds) != 2)
> > return false;
> >
> > should work here.
>
> Unfortunately, that doesn't work. We run into another assert in
> copy_cond_phi_nodes:
> ...
> /* Cond phi nodes should have exactly two arguments. */
> gcc_assert (2 == EDGE_COUNT (bb->preds));
> ...
Hah. So can we still do my suggested change and bail out conservatively
in Cond PHI node handling instead? Because the PHI node is clearly
_not_ a loop header PHI and the cond phi assert is also a latent bug.
> > Or replace this function with bb_loop_header_p (bb)
> > (works w/o loop info, the function seems to depend on loop info and
> > thus simply checking bb->loop_father->header == bb should work as well).
>
> I think that will run into the same assert.
Yes.
Richard.
> Thanks,
> - Tom
>
>
>
--
Richard Biener <rguenther@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nuernberg)