Re: [PATCH] match.pd: add the inclusive or dual of the masked comparison rule

On 8/4/2026 4:03 AM, [email protected] wrote:
> From: Kyrylo Tkachov <[email protected]>
>
> (X & C) == (Y & C) already folds to ((X ^ Y) & C) == 0.  The dual was
> missing: two values ored with the same constant agree on the bits that
> constant forces, so only the bits outside it can differ.
>
>    int f (unsigned char a, unsigned char b) { return (a | 32) == (b | 32); }
>
> aarch64 -O2 before:
>
> 	orr	w1, w1, 32
> 	orr	w0, w0, 32
> 	cmp	w1, w0
> 	cset	w0, eq
>
> after:
>
> 	eor	w0, w0, w1
> 	tst	w0, 223
> 	cset	w0, eq
>
> This is the case insensitive ASCII comparison, and any equality of two
> values on a masked field.  The rule sits directly beside its bit_and dual,
> inside the same eq and ne iterator.
>
> Bootstrapped and tested on aarch64-none-linux-gnu.
> Ok for trunk?
> Thanks,
> Kyrill
>
> gcc/ChangeLog:
>
> 	* match.pd ((X | C) ==/!= (Y | C)): New simplification.
>
> gcc/testsuite/ChangeLog:
>
> 	* gcc.dg/tree-ssa/ior-cmp-xor-1.c: New test.
>
> Signed-off-by: Kyrylo Tkachov <[email protected]>
OK.

Jeff