[Bug rtl-optimization/46878] [4.6 regression] V850 ICE in in maybe_add_or_update_dep_1, at sched-deps.c:854

["law at redhat dot com" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46878

--- Comment #20 from Jeffrey A. Law <law at redhat dot com> 2011-01-26 14:56:14 UTC ---
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On 01/26/11 07:51, mikpe at it dot uu.se wrote:
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46878
> 
> Mikael Pettersson <mikpe at it dot uu.se> changed:
> 
>            What    |Removed                     |Added
> ----------------------------------------------------------------------------
>                  CC|                            |mikpe at it dot uu.se
> 
> --- Comment #19 from Mikael Pettersson <mikpe at it dot uu.se> 2011-01-26 14:50:28 UTC ---
> (In reply to comment #18)
>> Note we're seeing this failure on m68k as well and it's a regression.
> 
> Could it be related to PR46856 (a HAVE_cc0 postreload regression from r162270
> that's breaking m68k-linux)?
It's related in the sense that both are problems with cc0 targets, but I
doubt the underlying root cause is the same.

jeff

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--- Comment #21 from Jeffrey A. Law <law at redhat dot com> 2011-01-26 15:23:15 UTC ---
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On 01/25/11 16:42, dj at redhat dot com wrote:
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46878
> 
> DJ Delorie <dj at redhat dot com> changed:
> 
>            What    |Removed                     |Added
> ----------------------------------------------------------------------------
>   Attachment #23074|0                           |1
>         is obsolete|                            |
> 
> --- Comment #16 from DJ Delorie <dj at redhat dot com> 2011-01-25 23:41:53 UTC ---
> Created attachment 23126
>   --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=23126
> alternate patch 3
> 
> Another patch attempt.  In this case, we add a check for the implied dependency
> created by a cc0 setter/user pair to insn_a_feeds_b() so that try_combine()
> knows that the cc0 setter is needed if the user is needed.
I think you're on the right track here.  I want to look at it a bit
more, but this might be "it".

FWIW, this code was a relatively recent addition to combine to support
four insn combinations and just happens to be the code I was concerned
might not be cc0-safe.

jeff

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--- Comment #22 from Jeffrey A. Law <law at redhat dot com> 2011-01-26 16:40:32 UTC ---
Patch attempt #3 is OK.  Please keep an eye out for complains about cc0 targets
not creating loop (dbra) insns.  That's my only worry.  I don't think it's
going to be a problem, but I can't completely rule it out.

Thanks for your patience,
Jeff