From: Jeff Law <law@redhat.com>
To: Teresa Johnson <tejohnson@google.com>,
"gcc-patches@gcc.gnu.org" <gcc-patches@gcc.gnu.org>
Cc: David Li <davidxl@google.com>
Subject: Re: [PATCH] Fix segfault in FRE during SCC value numbering
Date: Wed, 15 Jan 2014 18:46:00 -0000 [thread overview]
Message-ID: <52D6D76E.5050009@redhat.com> (raw)
In-Reply-To: <CAAe5K+UcnQhUZ6WdOLdMSABa+9FTQLE+jiUJ_QrZ2BwvhAf_gA@mail.gmail.com>
On 01/15/14 10:07, Teresa Johnson wrote:
> Handle NULL vdef for call in the case where we have a matching vnresult
> that has a vdef (it already handles the NULL vdef case when !vnresult). This
> can happen for promoted indirect calls if the fallback indirect call
> (which has a vdef) can be proven equivalent to the promoted direct call
> (which might not have a vdef).
>
> This occurred for a case where we had a promoted indirect call,
> where FRE determined that the promoted direct call and the fall-back indirect
> call were equivalent (since earlier it determined that the function pointer
> was always set to that target). The indirect call had been analyzed by
> visit_reference_op_call first, and had a VDEF. The direct call did not have a
> VDEF, presumably because it was a leaf function in the same module without any
> stores. But visit_reference_op_call unconditionally calls set_ssa_val_to when
> the previous vnresult had a vdef, leading to a seg fault in this case.
> If we had analyzed the direct call first the failure wouldn't have occurred
> since the !vnresult case guards the call to set_ssa_val_to with a check
> for a NULL vdef, and the subsequent handling of the indirect call would
> also not call set_ssa_val_to since vnresult would have had a null result_vdef.
>
> Bootstrapped and tested on x86_64-unknown-linux-gnu. Ok for trunk?
>
> 2014-01-15 Teresa Johnson <tejohnson@google.com>
>
> * tree-ssa-sccvn.c (visit_reference_op_call): Handle NULL vdef.
The patch is OK. Given this was an ICE, do you have a reduced test we
can add to the regression suite? I realize that order of visiting in
the SCC is important to trigger, but a regression test would still be
useful.
Thanks,
Jeff
next prev parent reply other threads:[~2014-01-15 18:46 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-15 17:07 Teresa Johnson
2014-01-15 18:46 ` Jeff Law [this message]
2014-01-15 20:00 ` Teresa Johnson
2014-01-15 21:17 ` Teresa Johnson
2014-01-15 21:23 ` Xinliang David Li
2014-01-15 21:33 ` Teresa Johnson
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