Re: [PATCH] combine: Fix simplify_comparison AND handling for WORD_REGISTER_OPERATIONS targets [PR109040]

[Jakub Jelinek <jakub@redhat.com>]

On Sat, Apr 08, 2023 at 06:25:32PM -0600, Jeff Law wrote:
> 
> 
> On 4/6/23 08:21, Eric Botcazou wrote:
> 
> > > So, perhaps just in the return op0; case add further code for
> > > WORD_REGISTER_OPERATIONS and sub-word modes which will call nonzero_bits
> > > again for the word mode and decide if it is still safe.
> > 
> > Does it work to just replace mode by word_mode in the calls to nonzero_bits?
> It helps marginally -- basically we defer mucking up the code a bit.  We
> then hit this in simplify_and_const_int_1:
> 
> 
>   /* See what bits may be nonzero in VAROP.  Unlike the general case of
>      a call to nonzero_bits, here we don't care about bits outside
>      MODE.  */
> 
>   nonzero = nonzero_bits (varop, mode) & GET_MODE_MASK (mode);
> 
> That just seems wrong for WORD_REGISTER_OPERATIONS targets.
> 
> 
> Hacking both locations in a similar manner fixes the test.

If so, can you post that in patch form and can we go with that version
plus the testcase (e.g. from the first patch I've posted where I've changed
dse)?

	Jakub