RE: [PATCH] Allow patterns in SLP reductions
On Mon, 13 May 2024, Tamar Christina wrote:
> > -Original Message-
> > From: Richard Biener
> > Sent: Friday, May 10, 2024 2:07 PM
> > To: Richard Biener
> > Cc: gcc-patches@gcc.gnu.org
> > Subject: Re: [PATCH] Allow patterns in SLP reductions
> >
> > On Fri, Mar 1, 2024 at 10:21 AM Richard Biener wrote:
> > >
> > > The following removes the over-broad rejection of patterns for SLP
> > > reductions which is done by removing them from LOOP_VINFO_REDUCTIONS
> > > during pattern detection. That's also insufficient in case the
> > > pattern only appears on the reduction path. Instead this implements
> > > the proper correctness check in vectorizable_reduction and guides
> > > SLP discovery to heuristically avoid forming later invalid groups.
> > >
> > > I also couldn't find any testcase that FAILs when allowing the SLP
> > > reductions to form so I've added one.
> > >
> > > I came across this for single-lane SLP reductions with the all-SLP
> > > work where we rely on patterns to properly vectorize COND_EXPR
> > > reductions.
> > >
> > > Bootstrapped and tested on x86_64-unknown-linux-gnu, queued for stage1.
> >
> > Re-bootstrapped/tested, r15-361-g52d4691294c847
>
> Awesome!
>
> Does this now allow us to write new reductions using patterns? i.e.
> widening reductions?
Yes (SLP reductions, that is). This is really only for SLP reductions
(not SLP reduction chains, not non-SLP reductions). So it's just
a corner-case but since with SLP-only non-SLP reductions become
SLP reductions with a single lane that was important to fix ;)
Richard.
> Cheers,
> Tamar
> >
> > Richard.
> >
> > > Richard.
> > >
> > > * tree-vect-patterns.cc (vect_pattern_recog_1): Do not
> > > remove reductions involving patterns.
> > > * tree-vect-loop.cc (vectorizable_reduction): Reject SLP
> > > reduction groups with multiple lane-reducing reductions.
> > > * tree-vect-slp.cc (vect_analyze_slp_instance): When discovering
> > > SLP reduction groups avoid including lane-reducing ones.
> > >
> > > * gcc.dg/vect/vect-reduc-sad-9.c: New testcase.
> > > ---
> > > gcc/testsuite/gcc.dg/vect/vect-reduc-sad-9.c | 68
> > > gcc/tree-vect-loop.cc| 15 +
> > > gcc/tree-vect-patterns.cc| 13
> > > gcc/tree-vect-slp.cc | 26 +---
> > > 4 files changed, 101 insertions(+), 21 deletions(-)
> > > create mode 100644 gcc/testsuite/gcc.dg/vect/vect-reduc-sad-9.c
> > >
> > > diff --git a/gcc/testsuite/gcc.dg/vect/vect-reduc-sad-9.c
> > b/gcc/testsuite/gcc.dg/vect/vect-reduc-sad-9.c
> > > new file mode 100644
> > > index 000..3c6af4510f4
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.dg/vect/vect-reduc-sad-9.c
> > > @@ -0,0 +1,68 @@
> > > +/* Disabling epilogues until we find a better way to deal with scans. */
> > > +/* { dg-additional-options "--param vect-epilogues-nomask=0" } */
> > > +/* { dg-additional-options "-msse4.2" { target { x86_64-*-* i?86-*-* } }
> > > } */
> > > +/* { dg-require-effective-target vect_usad_char } */
> > > +
> > > +#include
> > > +#include "tree-vect.h"
> > > +
> > > +#define N 64
> > > +
> > > +unsigned char X[N] __attribute__ ((__aligned__(__BIGGEST_ALIGNMENT__)));
> > > +unsigned char Y[N] __attribute__ ((__aligned__(__BIGGEST_ALIGNMENT__)));
> > > +int abs (int);
> > > +
> > > +/* Sum of absolute differences between arrays of unsigned char types.
> > > + Detected as a sad pattern.
> > > + Vectorized on targets that support sad for unsigned chars. */
> > > +
> > > +__attribute__ ((noinline)) int
> > > +foo (int len, int *res2)
> > > +{
> > > + int i;
> > > + int result = 0;
> > > + int result2 = 0;
> > > +
> > > + for (i = 0; i < len; i++)
> > > +{
> > > + /* Make sure we are not using an SLP reduction for this. */
> > > + result += abs (X[2*i] - Y[2*i]);
> > > + result2 += abs (X[2*i + 1] - Y[2*i + 1]);
> > > +}
> > > +
> > > + *res2 = result2;
> > > + return result;
> > > +}
> > > +
> > > +
> > > +int
> > > +main (void)
> > > +{
> > > + i
RE: [PATCH] Allow patterns in SLP reductions
> -Original Message-
> From: Richard Biener
> Sent: Friday, May 10, 2024 2:07 PM
> To: Richard Biener
> Cc: gcc-patches@gcc.gnu.org
> Subject: Re: [PATCH] Allow patterns in SLP reductions
>
> On Fri, Mar 1, 2024 at 10:21 AM Richard Biener wrote:
> >
> > The following removes the over-broad rejection of patterns for SLP
> > reductions which is done by removing them from LOOP_VINFO_REDUCTIONS
> > during pattern detection. That's also insufficient in case the
> > pattern only appears on the reduction path. Instead this implements
> > the proper correctness check in vectorizable_reduction and guides
> > SLP discovery to heuristically avoid forming later invalid groups.
> >
> > I also couldn't find any testcase that FAILs when allowing the SLP
> > reductions to form so I've added one.
> >
> > I came across this for single-lane SLP reductions with the all-SLP
> > work where we rely on patterns to properly vectorize COND_EXPR
> > reductions.
> >
> > Bootstrapped and tested on x86_64-unknown-linux-gnu, queued for stage1.
>
> Re-bootstrapped/tested, r15-361-g52d4691294c847
Awesome!
Does this now allow us to write new reductions using patterns? i.e. widening
reductions?
Cheers,
Tamar
>
> Richard.
>
> > Richard.
> >
> > * tree-vect-patterns.cc (vect_pattern_recog_1): Do not
> > remove reductions involving patterns.
> > * tree-vect-loop.cc (vectorizable_reduction): Reject SLP
> > reduction groups with multiple lane-reducing reductions.
> > * tree-vect-slp.cc (vect_analyze_slp_instance): When discovering
> > SLP reduction groups avoid including lane-reducing ones.
> >
> > * gcc.dg/vect/vect-reduc-sad-9.c: New testcase.
> > ---
> > gcc/testsuite/gcc.dg/vect/vect-reduc-sad-9.c | 68
> > gcc/tree-vect-loop.cc| 15 +
> > gcc/tree-vect-patterns.cc| 13
> > gcc/tree-vect-slp.cc | 26 +---
> > 4 files changed, 101 insertions(+), 21 deletions(-)
> > create mode 100644 gcc/testsuite/gcc.dg/vect/vect-reduc-sad-9.c
> >
> > diff --git a/gcc/testsuite/gcc.dg/vect/vect-reduc-sad-9.c
> b/gcc/testsuite/gcc.dg/vect/vect-reduc-sad-9.c
> > new file mode 100644
> > index 000..3c6af4510f4
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/vect/vect-reduc-sad-9.c
> > @@ -0,0 +1,68 @@
> > +/* Disabling epilogues until we find a better way to deal with scans. */
> > +/* { dg-additional-options "--param vect-epilogues-nomask=0" } */
> > +/* { dg-additional-options "-msse4.2" { target { x86_64-*-* i?86-*-* } } }
> > */
> > +/* { dg-require-effective-target vect_usad_char } */
> > +
> > +#include
> > +#include "tree-vect.h"
> > +
> > +#define N 64
> > +
> > +unsigned char X[N] __attribute__ ((__aligned__(__BIGGEST_ALIGNMENT__)));
> > +unsigned char Y[N] __attribute__ ((__aligned__(__BIGGEST_ALIGNMENT__)));
> > +int abs (int);
> > +
> > +/* Sum of absolute differences between arrays of unsigned char types.
> > + Detected as a sad pattern.
> > + Vectorized on targets that support sad for unsigned chars. */
> > +
> > +__attribute__ ((noinline)) int
> > +foo (int len, int *res2)
> > +{
> > + int i;
> > + int result = 0;
> > + int result2 = 0;
> > +
> > + for (i = 0; i < len; i++)
> > +{
> > + /* Make sure we are not using an SLP reduction for this. */
> > + result += abs (X[2*i] - Y[2*i]);
> > + result2 += abs (X[2*i + 1] - Y[2*i + 1]);
> > +}
> > +
> > + *res2 = result2;
> > + return result;
> > +}
> > +
> > +
> > +int
> > +main (void)
> > +{
> > + int i;
> > + int sad;
> > +
> > + check_vect ();
> > +
> > + for (i = 0; i < N/2; i++)
> > +{
> > + X[2*i] = i;
> > + Y[2*i] = N/2 - i;
> > + X[2*i+1] = i;
> > + Y[2*i+1] = 0;
> > + __asm__ volatile ("");
> > +}
> > +
> > +
> > + int sad2;
> > + sad = foo (N/2, );
> > + if (sad != (N/2)*(N/4))
> > +abort ();
> > + if (sad2 != (N/2-1)*(N/2)/2)
> > +abort ();
> > +
> > + return 0;
> > +}
> > +
> > +/* { dg-final { scan-tree-dump "vect_recog_sad_pattern: detected" "vect" }
> > } */
> > +/* { dg-final { scan-tree-dump-times "vectorized 1 loops" 1 "vect" }
Re: [PATCH] Allow patterns in SLP reductions
On Fri, Mar 1, 2024 at 10:21 AM Richard Biener wrote:
>
> The following removes the over-broad rejection of patterns for SLP
> reductions which is done by removing them from LOOP_VINFO_REDUCTIONS
> during pattern detection. That's also insufficient in case the
> pattern only appears on the reduction path. Instead this implements
> the proper correctness check in vectorizable_reduction and guides
> SLP discovery to heuristically avoid forming later invalid groups.
>
> I also couldn't find any testcase that FAILs when allowing the SLP
> reductions to form so I've added one.
>
> I came across this for single-lane SLP reductions with the all-SLP
> work where we rely on patterns to properly vectorize COND_EXPR
> reductions.
>
> Bootstrapped and tested on x86_64-unknown-linux-gnu, queued for stage1.
Re-bootstrapped/tested, r15-361-g52d4691294c847
Richard.
> Richard.
>
> * tree-vect-patterns.cc (vect_pattern_recog_1): Do not
> remove reductions involving patterns.
> * tree-vect-loop.cc (vectorizable_reduction): Reject SLP
> reduction groups with multiple lane-reducing reductions.
> * tree-vect-slp.cc (vect_analyze_slp_instance): When discovering
> SLP reduction groups avoid including lane-reducing ones.
>
> * gcc.dg/vect/vect-reduc-sad-9.c: New testcase.
> ---
> gcc/testsuite/gcc.dg/vect/vect-reduc-sad-9.c | 68
> gcc/tree-vect-loop.cc| 15 +
> gcc/tree-vect-patterns.cc| 13
> gcc/tree-vect-slp.cc | 26 +---
> 4 files changed, 101 insertions(+), 21 deletions(-)
> create mode 100644 gcc/testsuite/gcc.dg/vect/vect-reduc-sad-9.c
>
> diff --git a/gcc/testsuite/gcc.dg/vect/vect-reduc-sad-9.c
> b/gcc/testsuite/gcc.dg/vect/vect-reduc-sad-9.c
> new file mode 100644
> index 000..3c6af4510f4
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/vect/vect-reduc-sad-9.c
> @@ -0,0 +1,68 @@
> +/* Disabling epilogues until we find a better way to deal with scans. */
> +/* { dg-additional-options "--param vect-epilogues-nomask=0" } */
> +/* { dg-additional-options "-msse4.2" { target { x86_64-*-* i?86-*-* } } } */
> +/* { dg-require-effective-target vect_usad_char } */
> +
> +#include
> +#include "tree-vect.h"
> +
> +#define N 64
> +
> +unsigned char X[N] __attribute__ ((__aligned__(__BIGGEST_ALIGNMENT__)));
> +unsigned char Y[N] __attribute__ ((__aligned__(__BIGGEST_ALIGNMENT__)));
> +int abs (int);
> +
> +/* Sum of absolute differences between arrays of unsigned char types.
> + Detected as a sad pattern.
> + Vectorized on targets that support sad for unsigned chars. */
> +
> +__attribute__ ((noinline)) int
> +foo (int len, int *res2)
> +{
> + int i;
> + int result = 0;
> + int result2 = 0;
> +
> + for (i = 0; i < len; i++)
> +{
> + /* Make sure we are not using an SLP reduction for this. */
> + result += abs (X[2*i] - Y[2*i]);
> + result2 += abs (X[2*i + 1] - Y[2*i + 1]);
> +}
> +
> + *res2 = result2;
> + return result;
> +}
> +
> +
> +int
> +main (void)
> +{
> + int i;
> + int sad;
> +
> + check_vect ();
> +
> + for (i = 0; i < N/2; i++)
> +{
> + X[2*i] = i;
> + Y[2*i] = N/2 - i;
> + X[2*i+1] = i;
> + Y[2*i+1] = 0;
> + __asm__ volatile ("");
> +}
> +
> +
> + int sad2;
> + sad = foo (N/2, );
> + if (sad != (N/2)*(N/4))
> +abort ();
> + if (sad2 != (N/2-1)*(N/2)/2)
> +abort ();
> +
> + return 0;
> +}
> +
> +/* { dg-final { scan-tree-dump "vect_recog_sad_pattern: detected" "vect" } }
> */
> +/* { dg-final { scan-tree-dump-times "vectorized 1 loops" 1 "vect" } } */
> +
> diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
> index 35f1f8c7d42..13dcdba403a 100644
> --- a/gcc/tree-vect-loop.cc
> +++ b/gcc/tree-vect-loop.cc
> @@ -7703,6 +7703,21 @@ vectorizable_reduction (loop_vec_info loop_vinfo,
>return false;
> }
>
> + /* Lane-reducing ops also never can be used in a SLP reduction group
> + since we'll mix lanes belonging to different reductions. But it's
> + OK to use them in a reduction chain or when the reduction group
> + has just one element. */
> + if (lane_reduc_code_p
> + && slp_node
> + && !REDUC_GROUP_FIRST_ELEMENT (stmt_info)
> + && SLP_TREE_LANES (slp_node) > 1)
> +{
> + if (dump_enabled_p ())
> + dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
> +"lane-reducing reduction in reduction group.\n");
> + return false;
> +}
> +
>/* All uses but the last are expected to be defined in the loop.
> The last use is the reduction variable. In case of nested cycle this
> assumption is not true: we use reduc_index to record the index of the
> diff --git a/gcc/tree-vect-patterns.cc b/gcc/tree-vect-patterns.cc
> index d562f57920f..fe1ffba8688 100644
> --- a/gcc/tree-vect-patterns.cc
> +++ b/gcc/tree-vect-patterns.cc
> @@ -7172,7 +7172,6 @@ vect_pattern_recog_1
