> -----Original Message-----
> From: Andre Vieira (lists) <andre.simoesdiasvie...@arm.com>
> Sent: Friday, January 27, 2023 9:54 AM
> To: Kyrylo Tkachov <kyrylo.tkac...@arm.com>; gcc-patches@gcc.gnu.org
> Cc: Richard Earnshaw <richard.earns...@arm.com>
> Subject: Re: [PATCH 1/3] arm: Fix sign of MVE predicate mve_pred16_t [PR
> 107674]
>
>
>
> On 26/01/2023 15:02, Kyrylo Tkachov wrote:
> > Hi Andre,
> >
> >> -----Original Message-----
> >> From: Andre Vieira (lists) <andre.simoesdiasvie...@arm.com>
> >> Sent: Tuesday, January 24, 2023 1:41 PM
> >> To: gcc-patches@gcc.gnu.org
> >> Cc: Kyrylo Tkachov <kyrylo.tkac...@arm.com>; Richard Earnshaw
> >> <richard.earns...@arm.com>
> >> Subject: [PATCH 1/3] arm: Fix sign of MVE predicate mve_pred16_t [PR
> >> 107674]
> >>
> >> Hi,
> >>
> >> The ACLE defines mve_pred16_t as an unsigned short. This patch makes
> >> sure GCC treats the predicate as an unsigned type, rather than signed.
> >>
> >> Bootstrapped on aarch64-none-eabi and regression tested on arm-none-
> eabi
> >> and armeb-none-eabi for armv8.1-m.main+mve.fp.
> >>
> >> OK for trunk?
> >>
> >> gcc/ChangeLog:
> >>
> >> PR target/107674
> >> * config/arm/arm-builtins.cc (arm_simd_builtin_type): Rewrite to
> >> use
> >> new qualifiers parameter and use unsigned short type for MVE
> >> predicate.
> >> (arm_init_builtin): Call arm_simd_builtin_type with qualifiers
> >> parameter.
> >> (arm_init_crypto_builtins): Likewise.
> >>
> >> gcc/testsuite/ChangeLog:
> >>
> >> PR target/107674
> >> * gcc.target/arm/mve/mve_vpt.c: New test.
> >
> > diff --git a/gcc/config/arm/arm-builtins.cc b/gcc/config/arm/arm-builtins.cc
> > index
> 11d7478d9df69139802a9d42c09dd0de7480b60e..6c67cec93ff76a4b42f3a0b3
> 05f697142e88fcd9 100644
> > --- a/gcc/config/arm/arm-builtins.cc
> > +++ b/gcc/config/arm/arm-builtins.cc
> > @@ -1489,12 +1489,14 @@ arm_lookup_simd_builtin_type
> (machine_mode mode,
> > }
> >
> > static tree
> > -arm_simd_builtin_type (machine_mode mode, bool unsigned_p, bool
> poly_p)
> > +arm_simd_builtin_type (machine_mode mode, enum arm_type_qualifiers
> qualifiers)
> > {
> >
> > I think in C++ now we can leave out the "enum" here.
> >
> > diff --git a/gcc/testsuite/gcc.target/arm/mve/mve_vpt.c
> b/gcc/testsuite/gcc.target/arm/mve/mve_vpt.c
> > new file mode 100644
> > index
> 0000000000000000000000000000000000000000..26a565b79dd1348e361b3a
> a23a1d6e6d13bffce8
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/arm/mve/mve_vpt.c
> > @@ -0,0 +1,27 @@
> > +/* { dg-options "-O2" } */
> > +/* { dg-require-effective-target arm_v8_1m_mve_ok } */
> > +/* { dg-add-options arm_v8_1m_mve } */
> > +/* { dg-final { check-function-bodies "**" "" } } */
> > +#include <arm_mve.h>
> > +void test0 (uint8_t *a, uint8_t *b, uint8_t *c)
> > +{
> > + uint8x16_t va = vldrbq_u8 (a);
> > + uint8x16_t vb = vldrbq_u8 (b);
> > + mve_pred16_t p = vcmpeqq_u8 (va, vb);
> > + uint8x16_t vc = vaddq_x_u8 (va, vb, p);
> > + vstrbq_p_u8 (c, vc, p);
> > +}
> > +/*
> > +** test0:
> > +** vldrb.8 q2, \[r0\]
> > +** vldrb.8 q1, \[r1\]
> > +** vcmp.i8 eq, q2, q1
> > +** vmrs r3, p0 @ movhi
> > +** uxth r3, r3
> > +** vmsr p0, r3 @ movhi
> > +** vpst
> > +** vaddt.i8 q3, q2, q1
> > +** vpst
> > +** vstrbt.8 q3, \[r2\]
> > +** bx lr
> > +*/
> >
> > This explicit assembly matching looks quite fragile and sensitive to future
> scheduling and RA changes.
> > Is there something more targeted we could scan for to check that the
> predicate is unsigned now?
> No not really, as it's not unsigned everywhere, only in its intermediate
> representation between intrinsics. GCC is aware that mve_pred16_t is an
> unsigned short, so as soon as you try to use the value on its own or
> pass it as an argument or return, there is an implicit cast.
>
> I could make this particular test-case more robust by not checking
> specific registers. Though the sequence of loads-cmp-add-store will
> always be the same as it's data-dependent.
Yeah, I suspected as such. Ok, let's abstract the registers away (I think
check-function-bodies can use regex capturing to record particular registers)
then.
Thanks,
Kyrill
