Re: [PATCH v2 4/4] xtensa: Optimize bitwise AND operation with some specific forms of constants

[Max Filippov <jcmvbkbc@gmail.com>]

On Mon, Jun 13, 2022 at 9:39 AM Takayuki 'January June' Suwa
<jjsuwa_sys3175@yahoo.co.jp> wrote:
>
> On 2022/06/13 12:49, Max Filippov wrote:
> > Hi Suwa-san,
> hi!
>
> > This change produces a bunch of regression test failures in big-endian
> > configuration:
> bad news X(
> that point is what i was a little worried about...
>
> > E.g. for the test gcc.c-torture/execute/struct-ini-2.c
> > the following assembly code is generated now:
> > and the following code was generated before this change:
> -       .literal .LC1, -4096
> -       l32r    a10, .LC1
> -       and     a10, a8, a10
> +       extui   a10, a8, 16, 4  // wrong! must be 12, 4
> +       slli    a10, a10, 12
> and of course, '(zero_extract)' is endianness-sensitive.
> (ref. 14.11 Bit-Fields, gcc-internals)
>
> the all patches that i previouly posted do not match or emit '(zero_extract)', except for this case.
>
> ===
> This patch offers several insn-and-split patterns for bitwise AND with
> register and constant that can be represented as:
>
> i.   1's least significant N bits and the others 0's (17 <= N <= 31)
> ii.  1's most significant N bits and the others 0's (12 <= N <= 31)
> iii. M 1's sequence of bits and trailing N 0's bits, that cannot fit into a
>         "MOVI Ax, simm12" instruction (1 <= M <= 16, 1 <= N <= 30)
>
> And also offers shortcuts for conditional branch if each of the abovementioned
> operations is (not) equal to zero.
>
> gcc/ChangeLog:
>
>         * config/xtensa/predicates.md (shifted_mask_operand):
>         New predicate.
>         * config/xtensa/xtensa.md (*andsi3_const_pow2_minus_one):
>         New insn-and-split pattern.
>         (*andsi3_const_negative_pow2, *andsi3_const_shifted_mask,
>         *masktrue_const_pow2_minus_one, *masktrue_const_negative_pow2,
>         *masktrue_const_shifted_mask): Ditto.
> ---
>  gcc/config/xtensa/predicates.md |  10 ++
>  gcc/config/xtensa/xtensa.md     | 179 ++++++++++++++++++++++++++++++++
>  2 files changed, 189 insertions(+)

Regtested for target=xtensa-linux-uclibc, no new regressions.
Committed to master.

-- 
Thanks.
-- Max