Re: [vta, graphite?] propagate degenerate phi nodes into debug stmts

[Richard Guenther <richard.guenther@gmail.com>]

On Thu, Nov 19, 2009 at 4:05 AM, Alexandre Oliva <aoliva@redhat.com> wrote:
> On Nov 17, 2009, Richard Guenther <richard.guenther@gmail.com> wrote:
>
>>>> This looks odd.  SSA DEF operand iteration should walk the PHI defs
>>>> as well, so the change should not be necessary.
>
>>> I thought so, too, but by the time we get there, the operands of the PHI
>>> stmt have already been disconnected.
>
>> It shouldn't be.  Please try to figure out why instead.
>
> Gotta use a different FOR_EACH macro to handle PHI nodes.
>
> s/FOR_EACH_SSA_DEF_OPERAND/FOR_EACH_PHI_OR_STMT_DEF/ fixed it.
>
> In order to make sure no other such mistakes had been made in GCC, I
> added an assertion check in the iterator initializer and adjusted the
> uses of GIMPLE_PHI nodes that triggered the assertion, but that would
> have done nothing whatsoever in its absence.  I haven't looked into
> whether doing nothing is correct.
>
> Should I check this in?

Ah, hm.  The num_ssa_operands and delink_stmt_imm_use
changes were necessary because they triggered the assert?
I wonder if the callers were expecting them to be a no-op...

The tre-ssa-pre.c change is ok.  I think we should rather
let num_ssa_operands and delink_stmt_imm_use ICE on PHIs,
but I'd rather do this in stage1 - can you queue this patch until then?

Thanks,
Richard.

>
>
> --
> Alexandre Oliva, freedom fighter    http://FSFLA.org/~lxoliva/
> You must be the change you wish to see in the world. -- Gandhi
> Be Free! -- http://FSFLA.org/   FSF Latin America board member
> Free Software Evangelist      Red Hat Brazil Compiler Engineer
>
>