Re: RFA: PATCH to match.pd for c++/68385

[Marc Glisse <marc.glisse@inria.fr>]

On Sat, 21 Nov 2015, Richard Biener wrote:

> On November 20, 2015 8:58:15 PM GMT+01:00, Jason Merrill <jason@redhat.com> wrote:
>> In this bug, we hit the (A & sign-bit) != 0 -> A < 0 transformation.
>> Because of delayed folding, the operands aren't fully folded yet, so we
>>
>> have NOP_EXPRs around INTEGER_CSTs, and so calling wi::only_sign_bit_p
>> ICEs.  We've been seeing several similar bugs, where code calls
>> integer_zerop and therefore assumes that they have an INTEGER_CST, but
>> in fact integer_zerop does STRIP_NOPS.
>>
>> This patch changes the pattern to only match if the operand is actually
>>
>> an INTEGER_CST.  Alternatively we could call tree_strip_nop_conversions
>>
>> on the operand, but I would expect that to have issues when the
>> conversion changes the signedness of the type.
>>
>> OK if testing passes?
>
> What happens if we remove the nops stripping from integer_zerop?

I had the same reaction.

> Do other integer predicates strip nops?

Yes, they do.

I believe I added one or two of those, and the reason I added STRIP_NOPS 
is because they started as a copy-paste of integer_zerop...

-- 
Marc Glisse