Re: [PATCH v2] [PR96339] Optimise svlast[ab]

[Prathamesh Kulkarni <prathamesh.kulkarni@linaro.org>]

On Tue, 13 Jun 2023 at 12:38, Tejas Belagod via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
>
>
> From: Richard Sandiford <richard.sandiford@arm.com>
> Date: Monday, June 12, 2023 at 2:15 PM
> To: Tejas Belagod <Tejas.Belagod@arm.com>
> Cc: gcc-patches@gcc.gnu.org <gcc-patches@gcc.gnu.org>, Tejas Belagod <Tejas.Belagod@arm.com>
> Subject: Re: [PATCH v2] [PR96339] Optimise svlast[ab]
> Tejas Belagod <tejas.belagod@arm.com> writes:
> > From: Tejas Belagod <tbelagod@arm.com>
> >
> >   This PR optimizes an SVE intrinsics sequence where
> >     svlasta (svptrue_pat_b8 (SV_VL1), x)
> >   a scalar is selected based on a constant predicate and a variable vector.
> >   This sequence is optimized to return the correspoding element of a NEON
> >   vector. For eg.
> >     svlasta (svptrue_pat_b8 (SV_VL1), x)
> >   returns
> >     umov    w0, v0.b[1]
> >   Likewise,
> >     svlastb (svptrue_pat_b8 (SV_VL1), x)
> >   returns
> >      umov    w0, v0.b[0]
> >   This optimization only works provided the constant predicate maps to a range
> >   that is within the bounds of a 128-bit NEON register.
> >
> > gcc/ChangeLog:
> >
> >        PR target/96339
> >        * config/aarch64/aarch64-sve-builtins-base.cc (svlast_impl::fold): Fold sve
> >        calls that have a constant input predicate vector.
> >        (svlast_impl::is_lasta): Query to check if intrinsic is svlasta.
> >        (svlast_impl::is_lastb): Query to check if intrinsic is svlastb.
> >        (svlast_impl::vect_all_same): Check if all vector elements are equal.
> >
> > gcc/testsuite/ChangeLog:
> >
> >        PR target/96339
> >        * gcc.target/aarch64/sve/acle/general-c/svlast.c: New.
> >        * gcc.target/aarch64/sve/acle/general-c/svlast128_run.c: New.
> >        * gcc.target/aarch64/sve/acle/general-c/svlast256_run.c: New.
> >        * gcc.target/aarch64/sve/pcs/return_4.c (caller_bf16): Fix asm
> >        to expect optimized code for function body.
> >        * gcc.target/aarch64/sve/pcs/return_4_128.c (caller_bf16): Likewise.
> >        * gcc.target/aarch64/sve/pcs/return_4_256.c (caller_bf16): Likewise.
> >        * gcc.target/aarch64/sve/pcs/return_4_512.c (caller_bf16): Likewise.
> >        * gcc.target/aarch64/sve/pcs/return_4_1024.c (caller_bf16): Likewise.
> >        * gcc.target/aarch64/sve/pcs/return_4_2048.c (caller_bf16): Likewise.
> >        * gcc.target/aarch64/sve/pcs/return_5.c (caller_bf16): Likewise.
> >        * gcc.target/aarch64/sve/pcs/return_5_128.c (caller_bf16): Likewise.
> >        * gcc.target/aarch64/sve/pcs/return_5_256.c (caller_bf16): Likewise.
> >        * gcc.target/aarch64/sve/pcs/return_5_512.c (caller_bf16): Likewise.
> >        * gcc.target/aarch64/sve/pcs/return_5_1024.c (caller_bf16): Likewise.
> >        * gcc.target/aarch64/sve/pcs/return_5_2048.c (caller_bf16): Likewise.
>
> OK, thanks.
>
> Applied on master, thanks.
Hi Tejas,
This seems to break aarch64 bootstrap build with following error due
to -Wsign-compare diagnostic:
00:18:19 /home/tcwg-buildslave/workspace/tcwg_gnu_6/abe/snapshots/gcc.git~master/gcc/config/aarch64/aarch64-sve-builtins-base.cc:1133:35:
error: comparison of integer expressions of different signedness:
‘int’ and ‘long unsigned int’ [-Werror=sign-compare]
00:18:19  1133 |                 for (i = npats; i < enelts; i += step_1)
00:18:19          |                                 ~~^~~~~~~~
00:30:46 abe-debug-build: cc1plus: all warnings being treated as errors
00:30:46 abe-debug-build: make[3]: ***
[/home/tcwg-buildslave/workspace/tcwg_gnu_6/abe/snapshots/gcc.git~master/gcc/config/aarch64/t-aarch64:96:
aarch64-sve-builtins-base.o] Error 1

Thanks,
Prathamesh
>
> Tejas.
>
>
> Richard