RE: [PATCH 2/6] aarch64: Allow moves after tied-register intrinsics

[Kyrylo Tkachov via Gcc-patches]

> -----Original Message-----
> From: Richard Sandiford <richard.sandif...@arm.com>
> Sent: Monday, May 15, 2023 3:18 PM
> To: Kyrylo Tkachov <kyrylo.tkac...@arm.com>
> Cc: gcc-patches@gcc.gnu.org
> Subject: Re: [PATCH 2/6] aarch64: Allow moves after tied-register intrinsics
> 
> Kyrylo Tkachov <kyrylo.tkac...@arm.com> writes:
> > Hi Richard,
> >
> >> -----Original Message-----
> >> From: Gcc-patches <gcc-patches-
> >> bounces+kyrylo.tkachov=arm....@gcc.gnu.org> On Behalf Of Richard
> >> Sandiford via Gcc-patches
> >> Sent: Tuesday, May 9, 2023 7:48 AM
> >> To: gcc-patches@gcc.gnu.org
> >> Cc: Richard Sandiford <richard.sandif...@arm.com>
> >> Subject: [PATCH 2/6] aarch64: Allow moves after tied-register intrinsics
> >>
> >> Some ACLE intrinsics map to instructions that tie the output
> >> operand to an input operand.  If all the operands are allocated
> >> to different registers, and if MOVPRFX can't be used, we will need
> >> a move either before the instruction or after it.  Many tests only
> >> matched the "before" case; this patch makes them accept the "after"
> >> case too.
> >>
> >> gcc/testsuite/
> >>       * gcc.target/aarch64/advsimd-intrinsics/bfcvtnq2-untied.c: Allow
> >>       moves to occur after the intrinsic instruction, rather than requiring
> >>       them to happen before.
> >>       * gcc.target/aarch64/advsimd-intrinsics/bfdot-1.c: Likewise.
> >>       * gcc.target/aarch64/advsimd-intrinsics/vdot-3-1.c: Likewise.
> >
> > I'm seeing some dot-product intrinsics failures:
> > FAIL: gcc.target/aarch64/advsimd-intrinsics/bfdot-2.c   -O1   
> > check-function-
> bodies ufoo_untied
> > FAIL: gcc.target/aarch64/advsimd-intrinsics/bfdot-2.c   -O1   
> > check-function-
> bodies ufooq_lane_untied
> > FAIL: gcc.target/aarch64/advsimd-intrinsics/bfdot-2.c   -O2   
> > check-function-
> bodies ufoo_untied
> > FAIL: gcc.target/aarch64/advsimd-intrinsics/bfdot-2.c   -O2   
> > check-function-
> bodies ufooq_lane_untied
> > FAIL: gcc.target/aarch64/advsimd-intrinsics/bfdot-2.c   -O2 -flto -fno-use-
> linker-plugin -flto-partition=none   check-function-bodies ufoo_untied
> > FAIL: gcc.target/aarch64/advsimd-intrinsics/bfdot-2.c   -O2 -flto -fno-use-
> linker-plugin -flto-partition=none   check-function-bodies ufooq_lane_untied
> > FAIL: gcc.target/aarch64/advsimd-intrinsics/bfdot-2.c   -O3 -g   check-
> function-bodies ufoo_untied
> > FAIL: gcc.target/aarch64/advsimd-intrinsics/bfdot-2.c   -O3 -g   check-
> function-bodies ufooq_lane_untied
> > FAIL: gcc.target/aarch64/advsimd-intrinsics/bfdot-2.c   -Og -g   check-
> function-bodies ufoo_untied
> > FAIL: gcc.target/aarch64/advsimd-intrinsics/bfdot-2.c   -Og -g   check-
> function-bodies ufooq_lane_untied
> > FAIL: gcc.target/aarch64/advsimd-intrinsics/bfdot-2.c   -Os   
> > check-function-
> bodies ufoo_untied
> > FAIL: gcc.target/aarch64/advsimd-intrinsics/bfdot-2.c   -Os   
> > check-function-
> bodies ufooq_lane_untied
> > FAIL: gcc.target/aarch64/advsimd-intrinsics/vdot-3-2.c   -O1   check-
> function-bodies ufoo_untied
> > FAIL: gcc.target/aarch64/advsimd-intrinsics/vdot-3-2.c   -O1   check-
> function-bodies ufooq_laneq_untied
> > FAIL: gcc.target/aarch64/advsimd-intrinsics/vdot-3-2.c   -O2   check-
> function-bodies ufoo_untied
> > FAIL: gcc.target/aarch64/advsimd-intrinsics/vdot-3-2.c   -O2   check-
> function-bodies ufooq_laneq_untied
> > FAIL: gcc.target/aarch64/advsimd-intrinsics/vdot-3-2.c   -O2 -flto -fno-use-
> linker-plugin -flto-partition=none   check-function-bodies ufoo_untied
> > FAIL: gcc.target/aarch64/advsimd-intrinsics/vdot-3-2.c   -O2 -flto -fno-use-
> linker-plugin -flto-partition=none   check-function-bodies
> ufooq_laneq_untied
> > FAIL: gcc.target/aarch64/advsimd-intrinsics/vdot-3-2.c   -O3 -g   check-
> function-bodies ufoo_untied
> > FAIL: gcc.target/aarch64/advsimd-intrinsics/vdot-3-2.c   -O3 -g   check-
> function-bodies ufooq_laneq_untied
> > FAIL: gcc.target/aarch64/advsimd-intrinsics/vdot-3-2.c   -Og -g   check-
> function-bodies ufoo_untied
> > FAIL: gcc.target/aarch64/advsimd-intrinsics/vdot-3-2.c   -Og -g   check-
> function-bodies ufooq_laneq_untied
> > FAIL: gcc.target/aarch64/advsimd-intrinsics/vdot-3-2.c   -Os   
> > check-function-
> bodies ufoo_untied
> > FAIL: gcc.target/aarch64/advsimd-intrinsics/vdot-3-2.c   -Os   
> > check-function-
> bodies ufooq_laneq_untied
> 
> Ugh.  Big-endian.  Hadn't thought about that being an issue.
> Was testing natively on little-endian aarch64-linux-gnu and
> didn't see these.

FWIW this is on a little-endian aarch64-none-elf configuration.
Maybe some defaults are different on bare-metal from Linux...

> 
> > From a quick inspection it looks like it's just an alternative regalloc that
> moves the mov + dot instructions around, similar to what you fixed in bfdot-
> 2.c and vdot-3-2.c.
> > I guess they need a similar adjustment?
> 
> Yeah, will fix.

Thanks!
Kyrill

> 
> Thanks,
> Richard