On Fri, 23 Feb 2024, Tamar Christina wrote:
> Hi All,
>
> In certain cases we can have a situation where the merge block has a vUSE
> virtual PHI and the exits do not. In this case for instance the exits lead
> to an abort so they have no virtual PHIs. If we have a store before the first
> exit and we move it to a later block during vectorization we update the vUSE
> chain.
>
> However the merge block is not an exit and is not visited by the update code.
>
> This patch fixes it by checking during moving if there are any out of loop
> uses
> of the vDEF that is the last_seen_vuse. Normally there wouldn't be any and
> things are skipped, but if there is then update that to the last vDEF in the
> exit block.
>
> Bootstrapped Regtested on aarch64-none-linux-gnu and
> x86_64-pc-linux-gnu no issues.
>
> Ok for master?
I think the problem is rather that BB13 misses the LC virtual PHI which
it requires because of the merge block. So this should be fixed during
peeling instead. There we assume the IV exit we choose will have
a virtual LC PHI if the loop needs one (but we choose the exit going
to unreachable () as IV exit ...). This assumption breaks down in this
case.
Let me try to fix this.
Richard.
> Thanks,
> Tamar
>
> gcc/ChangeLog:
>
> PR tree-optimizations/114068
> * tree-vect-loop.cc (move_early_exit_stmts): Update vUSE chain in merge
> block.
>
> gcc/testsuite/ChangeLog:
>
> PR tree-optimizations/114068
> * gcc.dg/vect/vect-early-break_118-pr114068.c: New test.
> * gcc.dg/vect/vect-early-break_119-pr114068.c: New test.
>
> --- inline copy of patch --
> diff --git a/gcc/testsuite/gcc.dg/vect/vect-early-break_118-pr114068.c
> b/gcc/testsuite/gcc.dg/vect/vect-early-break_118-pr114068.c
> new file mode 100644
> index
> 0000000000000000000000000000000000000000..b462a464b6603e718c5a283513ea586fc13e37ce
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/vect/vect-early-break_118-pr114068.c
> @@ -0,0 +1,23 @@
> +/* { dg-do compile } */
> +/* { dg-add-options vect_early_break } */
> +/* { dg-require-effective-target vect_early_break } */
> +/* { dg-require-effective-target vect_int } */
> +/* { dg-additional-options "-O3" } */
> +
> +/* { dg-final { scan-tree-dump "LOOP VECTORIZED" "vect" } } */
> +
> +struct h {
> + int b;
> + int f;
> +} k;
> +
> +void n(int m) {
> + struct h a = k;
> + for (int o = m; o; ++o) {
> + if (a.f)
> + __builtin_unreachable();
> + if (o > 1)
> + __builtin_unreachable();
> + *(&k.b + o) = 1;
> + }
> +}
> diff --git a/gcc/testsuite/gcc.dg/vect/vect-early-break_119-pr114068.c
> b/gcc/testsuite/gcc.dg/vect/vect-early-break_119-pr114068.c
> new file mode 100644
> index
> 0000000000000000000000000000000000000000..a65ef7b8c4901b2ada585f38fda436dc07d1e1de
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/vect/vect-early-break_119-pr114068.c
> @@ -0,0 +1,25 @@
> +/* { dg-do compile } */
> +/* { dg-add-options vect_early_break } */
> +/* { dg-require-effective-target vect_early_break } */
> +/* { dg-require-effective-target vect_int } */
> +/* { dg-additional-options "-O3" } */
> +
> +/* { dg-final { scan-tree-dump "LOOP VECTORIZED" "vect" } } */
> +
> +struct h {
> + int b;
> + int c;
> + int f;
> +} k;
> +
> +void n(int m) {
> + struct h a = k;
> + for (int o = m; o; ++o) {
> + if (a.f)
> + __builtin_unreachable();
> + if (o > 1)
> + __builtin_unreachable();
> + *(&k.b + o) = 1;
> + *(&k.c + o*m) = 2;
> + }
> +}
> diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
> index
> 35f1f8c7d4245135ace7ffff40ff9be548919587..44bd8032b55b1ef84fdf4fa9d6117304b7709d6f
> 100644
> --- a/gcc/tree-vect-loop.cc
> +++ b/gcc/tree-vect-loop.cc
> @@ -11837,6 +11837,27 @@ move_early_exit_stmts (loop_vec_info loop_vinfo)
> update_stmt (p);
> }
>
> + /* last_seen_vuse should now be the PHI in the loop header. Check for
> + any out of loop uses and update them to the vUSE on the loop latch. */
> + auto vuse_stmt = loop_vinfo->lookup_def (last_seen_vuse);
> + gphi *vuse_def;
> + if (vuse_stmt
> + && (vuse_def = dyn_cast <gphi *> (STMT_VINFO_STMT (vuse_stmt))))
> + {
> + imm_use_iterator iter;
> + use_operand_p use_p;
> + gimple *use_stmt;
> + auto loop = LOOP_VINFO_LOOP (loop_vinfo);
> + tree vuse = PHI_ARG_DEF_FROM_EDGE (vuse_def, loop_latch_edge (loop));
> + FOR_EACH_IMM_USE_STMT (use_stmt, iter, last_seen_vuse)
> + {
> + if (flow_bb_inside_loop_p (loop, use_stmt->bb))
> + continue;
> + FOR_EACH_IMM_USE_ON_STMT (use_p, iter)
> + SET_USE (use_p, vuse);
> + }
> + }
> +
> /* And update the LC PHIs on exits. */
> for (edge e : get_loop_exit_edges (LOOP_VINFO_LOOP (loop_vinfo)))
> if (!dominated_by_p (CDI_DOMINATORS, e->src, dest_bb))
>
>
>
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
