On Tue, 9 May 2017, Richard Biener wrote:
> On Fri, 5 May 2017, Christophe Lyon wrote:
>
> > Hi Richard,
> >
> >
> > On 3 May 2017 at 10:19, Richard Biener <rguent...@suse.de> wrote:
> > >
> > > The following extends the very simplistic cost modeling I added somewhen
> > > late in the release process to, for all unknown misaligned refs, also
> > > apply this model for loops containing stores.
> > >
> > > The model basically says it's useless to peel for alignment if there's
> > > only a single DR that is affected or if, in case we'll end up using
> > > hw-supported misaligned loads, the cost of misaligned loads is the same
> > > as of aligned ones. Previously we'd usually align one of the stores
> > > with the theory that this improves (precious) store-bandwith.
> > >
> > > Note this is only a so slightly conservative (aka less peeling). We'll
> > > still apply peeling for alignment if you make the testcase use +=
> > > because then we'll align both the load and the store from v1.
> > >
> > > Bootstrap / regtest running on x86_64-unknown-linux-gnu.
> > >
> > > Richard.
> > >
> > > 2017-05-03 Richard Biener <rguent...@suse.de>
> > >
> > > * tree-vect-data-refs.c (vect_enhance_data_refs_alignment):
> > > When all DRs have unknown misaligned do not always peel
> > > when there is a store but apply the same costing model as if
> > > there were only loads.
> > >
> > > * gcc.dg/vect/costmodel/x86_64/costmodel-alignpeel.c: New
> > > testcase.
> > >
> >
> > This patch (r247544) caused regressions on aarch64 and arm:
> > - PASS now FAIL [PASS => FAIL]:
> >
> > Executed from: gcc.dg/vect/vect.exp
> > gcc.dg/vect/vect-44.c -flto -ffat-lto-objects
> > scan-tree-dump-times vect "Alignment of access forced using peeling" 1
> > gcc.dg/vect/vect-44.c -flto -ffat-lto-objects
> > scan-tree-dump-times vect "Vectorizing an unaligned access" 2
> > gcc.dg/vect/vect-44.c scan-tree-dump-times vect "Alignment of
> > access forced using peeling" 1
> > gcc.dg/vect/vect-44.c scan-tree-dump-times vect "Vectorizing an
> > unaligned access" 2
> > gcc.dg/vect/vect-50.c -flto -ffat-lto-objects
> > scan-tree-dump-times vect "Alignment of access forced using peeling" 1
> > gcc.dg/vect/vect-50.c -flto -ffat-lto-objects
> > scan-tree-dump-times vect "Vectorizing an unaligned access" 2
> > gcc.dg/vect/vect-50.c scan-tree-dump-times vect "Alignment of
> > access forced using peeling" 1
> > gcc.dg/vect/vect-50.c scan-tree-dump-times vect "Vectorizing an
> > unaligned access" 2
>
> Ok, so the reason is that we no longer peel for alignment for
>
> for (i = 0; i < N; i++)
> {
> pa[i] = pb[i] * pc[i];
> }
>
> which is probably good. This is because the generic aarch64 cost model
> (and probaby also arm) has
>
> 1, /* vec_align_load_cost */
> 1, /* vec_unalign_load_cost */
> 1, /* vec_unalign_store_cost */
> 1, /* vec_store_cost */
>
> so there's no benefit in aligning. x86 generic tuning has
>
> 1, /* vec_align_load_cost. */
> 2, /* vec_unalign_load_cost. */
> 1, /* vec_store_cost. */
>
> and vec_unalign_store_cost sharing with vec_unalign_load_cost.
> That makes us still apply peeling.
>
> Fixing this with vect_ testsuite conditions is going to be tricky
> so the easiest is to simply disable peeling here.
>
> Tested on aarch64 and x86_64, committed.
>
> Richard.
>
> 2017-05-09 Richard Biener <rguent...@suse.de>
>
> * gcc.dg/vect/vect-44.c: Add --param vect-max-peeling-for-alignment=0
> and adjust.
> * gcc.dg/vect/vect-50.c: Likewise.
>
> Index: gcc/testsuite/gcc.dg/vect/vect-44.c
> ===================================================================
> --- gcc/testsuite/gcc.dg/vect/vect-44.c (revision 247782)
> +++ gcc/testsuite/gcc.dg/vect/vect-44.c (working copy)
> @@ -1,6 +1,7 @@
> +/* { dg-do compile } */
Without these changes. Those were for aarch64 cross testing.
Richard.
> /* { dg-require-effective-target vect_float } */
> +/* { dg-additional-options "--param vect-max-peeling-for-alignment=0" } */
>
> -#include <stdarg.h>
> #include "tree-vect.h"
>
> #define N 256
> @@ -65,7 +66,7 @@ int main (void)
> two loads to be aligned). */
>
> /* { dg-final { scan-tree-dump-times "vectorized 1 loops" 1 "vect" } } */
> -/* { dg-final { scan-tree-dump-times "Vectorizing an unaligned access" 2
> "vect" { xfail { vect_no_align && { ! vect_hw_misalign } } } } } */
> -/* { dg-final { scan-tree-dump-times "Alignment of access forced using
> peeling" 1 "vect" { xfail { { vect_no_align && { ! vect_hw_misalign } } || {!
> vector_alignment_reachable} } } } } */
> +/* { dg-final { scan-tree-dump-times "Vectorizing an unaligned access" 3
> "vect" { xfail { vect_no_align && { ! vect_hw_misalign } } } } } */
> +/* { dg-final { scan-tree-dump-times "Alignment of access forced using
> peeling" 0 "vect" { xfail { { vect_no_align && { ! vect_hw_misalign } } || {!
> vector_alignment_reachable} } } } } */
> /* { dg-final { scan-tree-dump-times "Alignment of access forced using
> versioning." 3 "vect" { target { vect_no_align && { ! vect_hw_misalign } } }
> } } */
> /* { dg-final { scan-tree-dump-times "Alignment of access forced using
> versioning." 1 "vect" { target { {! vector_alignment_reachable} && {{!
> vect_no_align} && {! vect_hw_misalign} } } } } } */
> Index: gcc/testsuite/gcc.dg/vect/vect-50.c
> ===================================================================
> --- gcc/testsuite/gcc.dg/vect/vect-50.c (revision 247782)
> +++ gcc/testsuite/gcc.dg/vect/vect-50.c (working copy)
> @@ -1,6 +1,7 @@
> +/* { dg-do compile } */
> /* { dg-require-effective-target vect_float } */
> +/* { dg-additional-options "--param vect-max-peeling-for-alignment=0" } */
>
> -#include <stdarg.h>
> #include "tree-vect.h"
>
> #define N 256
> @@ -61,8 +62,8 @@ int main (void)
> align the store will not force the two loads to be aligned). */
>
> /* { dg-final { scan-tree-dump-times "vectorized 1 loops" 1 "vect" } } */
> -/* { dg-final { scan-tree-dump-times "Vectorizing an unaligned access" 2
> "vect" { xfail { vect_no_align && { ! vect_hw_misalign } } } } } */
> -/* { dg-final { scan-tree-dump-times "Vectorizing an unaligned access" 2
> "vect" { target vect_hw_misalign } } } */
> -/* { dg-final { scan-tree-dump-times "Alignment of access forced using
> peeling" 1 "vect" { xfail { { vect_no_align && { ! vect_hw_misalign } } || {!
> vector_alignment_reachable} } } } } */
> +/* { dg-final { scan-tree-dump-times "Vectorizing an unaligned access" 3
> "vect" { xfail { vect_no_align && { ! vect_hw_misalign } } } } } */
> +/* { dg-final { scan-tree-dump-times "Vectorizing an unaligned access" 3
> "vect" { target vect_hw_misalign } } } */
> +/* { dg-final { scan-tree-dump-times "Alignment of access forced using
> peeling" 0 "vect" { xfail { { vect_no_align && { ! vect_hw_misalign } } || {!
> vector_alignment_reachable} } } } } */
> /* { dg-final { scan-tree-dump-times "Alignment of access forced using
> versioning." 3 "vect" { target { vect_no_align && { ! vect_hw_misalign } } }
> } } */
> /* { dg-final { scan-tree-dump-times "Alignment of access forced using
> versioning." 1 "vect" { target { {! vector_alignment_reachable} && { {!
> vect_no_align } && {! vect_hw_misalign } } } } } } */
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
