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Re: [PATCH] Fix DCE REG_LIBCALL note moving from noop move insns (PR rtl-optimization/33644)
Paolo Bonzini wrote:
> Eric Botcazou wrote:
>>> If you don't see the practical advantage of being able to determine
>>> whether an insn is part of a libcall without having to walk the entire
>>> function to figure out whether you are allowed to touch an insn,
>>> please just remove it.
>>
>> I've posted a patch to that effect. It restores the correct
>> interpretation of libcall notes as optimization helpers rather than
>> optimization barriers as far as DCE is concerned and, thus,
>> eliminates the need for being able to determine whether an insn is
>> part of a libcall in dce.c.
>>
>> But I won't install it myself, given how controversial this issue has
>> become.
>> I therefore propose that a 3rd party decides here, and I'd suggest
>> Jakub.
>
> I agree that Jakub has a good hold of DCE but, if a DF reviewer is
> needed, I'm happy to help.
>
> I'm not extremely tied to REG_LIBCALL_ID, though in the long run I
> think it is a better solution than REG_LIBCALL/REG_RETVAL. However,
> it looks like there is no clean design for a new representation (for
> example, might the best thing be REG_LIBCALL_ID/REG_RETVAL?) that is
> also usable *for the entire transition* (covering the whole RTL
> pipeline). Also, we're in stage3. For all these reasons, I'm happy
> to ditch it at least momentarily.
>
> Paolo
thanks
kenny