Re: [PATCH][v2] match.pd: combine a pair of vector comparisons against zero

On 8/5/2026 5:45 AM, [email protected] wrote:
> From: Kyrylo Tkachov <[email protected]>
>
> A lane of A | B is zero exactly when the corresponding lanes of A and of B
> are both zero, so
>
>    (A == 0) & (B == 0)  ->  (A | B) == 0
>
> and the De Morgan dual for inequality.  The existing scalar rule already
> implements this identity.  Extend it to vector integers and use a view
> conversion when the operands differ only in element signedness.  Extend the
> related all-ones rule in the same way.
>
>    typedef int v4si __attribute__((vector_size (16)));
>    v4si f (v4si a, v4si b) { return (a == 0) & (b == 0); }
>
> aarch64 -O3 before:
>
> 	cmeq	v0.4s, v0.4s, #0
> 	cmeq	v1.4s, v1.4s, #0
> 	and	v0.16b, v0.16b, v1.16b
>
> after:
>
> 	orr	v0.16b, v0.16b, v1.16b
> 	cmeq	v0.4s, v0.4s, #0
>
> Add vector_nop_conversion_p for the element-wise property shared by these
> rules and the existing nop_convert matcher.
>
> Bootstrapped and tested on aarch64-none-linux-gnu.
> Ok for trunk?
> Thanks,
> Kyrill
>
> gcc/ChangeLog:
>
> 	* match.pd (nop_convert): Use vector_nop_conversion_p.
> 	((A == 0) & (B == 0), (A != 0) | (B != 0)): Extend the
> 	existing simplifications to vector operands.
> 	((A == -1) & (B == -1), (A != -1) | (B != -1)): Likewise.
> 	* tree.cc (vector_nop_conversion_p): New function.
> 	* tree.h (vector_nop_conversion_p): Declare.
>
> gcc/testsuite/ChangeLog:
>
> 	* gcc.dg/tree-ssa/vec-mask-zero-1.c: New test.
>
> Signed-off-by: Kyrylo Tkachov <[email protected]>
OK
jeff