On Wed, Sep 14, 2022 at 07:58:47AM +0000, Richard Biener wrote:
> > My change to match.pd (that added the two simplifications this patch
> > touches) results in more |/^/& assignments with pointer arguments,
> > but since r12-1608 we reject pointer operands for BIT_NOT_EXPR.
> >
> > Disallowing them for BIT_NOT_EXPR and allowing for BIT_{IOR,XOR,AND}_EXPR
> > leads to a match.pd maintainance nightmare (see one of the patches in the
> > PR), so either we want to allow pointer operand on BIT_NOT_EXPR (but then
> > we run into issues e.g. with the ranger which expects it can emulate
> > BIT_NOT_EXPR ~X as - 1 - X which doesn't work for pointers which don't
> > support MINUS_EXPR), or the following patch disallows pointer arguments
> > for all of BIT_{IOR,XOR,AND}_EXPR with the exception of BIT_AND_EXPR
> > with INTEGER_CST last operand (for simpler pointer realignment).
> > I had to tweak one reassoc optimization and the two match.pd
> > simplifications.
> >
> > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> OK.
Thanks.
> Did you check what breaks when we reverse the decision to allow
> BIT_AND_EXPR to align pointers alltogether? I think we don't
> have any
>
> (T')(((T)ptr) & CST) -> ptr & CST
I haven't tried that, but can try that next.
Would prefer a few days in between so if my current patch affects other
arches it is reported.
> I think for BIT_*_EXPR we want ANY_INTEGRAL_TYPE_P (well, likely
> not complex int, but ...). So if a patch to check that passes
> bootstrap that would be nice to have.
And can try that as the third step then.
Jakub
