Re: [PATCH] Handle PHI nodes w/o a argument (PR ipa/80205).

[Jeff Law <law@redhat.com>]

On 03/27/2017 08:27 AM, Richard Biener wrote:
> On Mon, Mar 27, 2017 at 4:14 PM, Richard Biener
> <richard.guenther@gmail.com> wrote:
>> On Mon, Mar 27, 2017 at 2:47 PM, Martin Liška <mliska@suse.cz> wrote:
>>> Hello.
>>>
>>> As described in the PR, we can create a PHI node in einline that has no argument.
>>> That can cause ICE in devirtualization and should be thus handled.
>>>
>>> Patch can bootstrap on ppc64le-redhat-linux and survives regression tests.
>>>
>>> Ready to be installed?
>>
>> We shouldn't ever have a PHI w/o argument.
>
> ;;   basic block 14, loop depth 0
> ;;    pred:
>   # SR.2_19 = PHI <>
> <L4> [0.00%]:
>   a::~a (&g);
>   resx 12
> ;;    succ:       17
>
> the CFG has not been cleaned up here (this block is unreachable).
>
> Hmm, I see we are called from fold_stmt.  I suppose we process
> statements_to_fold before removing unreachable blocks to not
> walk over dead stmts...  chicken-and-egg...
>
> Still not creating that PHI should be possible.
Can't speak for this specific example, but could it be the case that the 
PHI exists with arguments, then becomes unreachable resulting in a PHI 
with no arguments?

jeff