Re: [PATCH][AArch64][2/3] PR target/84164: Add ZERO_EXTRACT + LSHIFTRT pattern for BFXIL instruction

[Kyrill Tkachov <kyrylo.tkachov@foss.arm.com>]

Hi all,

I'm pinging this patch (https://gcc.gnu.org/ml/gcc-patches/2018-02/msg00444.html)
now that Jeff has approved the prerequisite simplify-rtx.c change (https://gcc.gnu.org/ml/gcc-patches/2018-03/msg00143.html) (thanks!)

Thanks,
Kyrill

On 08/02/18 17:10, Kyrill Tkachov wrote:
> Hi all,
>
> This is a followup to the other PR target/84164 patch [1] that fixes the testsuite regression
> gcc.target/aarch64/bfxil_1.c.
> The regression is that with the new subreg+masking simplification we no longer match the
> pattern for BFXIL that has the form:
> (set (zero_extract:DI (reg/v:DI 76 [ a ])
>         (const_int 8 [0x8])
>         (const_int 0 [0]))
>     (zero_extract:DI (reg/v:DI 76 [ a ])
>         (const_int 8 [0x8])
>         (const_int 16 [0x10])))
>
> This is now instead represented as:
> (set (zero_extract:DI (reg/v:DI 93 [ a ])
>         (const_int 8 [0x8])
>         (const_int 0 [0]))
>     (lshiftrt:DI (reg/v:DI 93 [ a ])
>         (const_int 16 [0x10])))
>
> As far as I can see the two are equivalent semantically and the LSHIFTRT form is a bit
> simpler, so I think the simplified form is valid, but we have no pattern to match it.
> This patch adds that pattern to catch this form as well.
> This fixes the aforementioned regression and bootstrap and testing on aarch64-none-linux-gnu
> shows no problem.
>
> Is this ok for trunk if the first patch goes in?
> Thanks,
> Kyrill
>
> [1] https://gcc.gnu.org/ml/gcc-patches/2018-02/msg00443.html
>
> 2018-02-08  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
>
>     PR target/84164
>     * config/aarch64/aarch64.md (*extr_insv_lower_reg_lshiftrt<mode>):
>     New pattern.