On Tue, 13 Feb 2024, Tamar Christina wrote:
> Hi All,
>
> When doing early break vectorization we should treat the final iteration as
> possibly being partial. This so that when we calculate the vector loop upper
> bounds we take into account that final iteration could have done some work.
>
> The attached testcase shows that if we don't then cunroll may unroll the loop
> an
> if the upper bound is wrong we lose a vector iteration.
>
> This is similar to how we adjust the scalar loop bounds for the PEELED case.
>
> Bootstrapped Regtested on aarch64-none-linux-gnu and
> x86_64-pc-linux-gnu no issues.
>
> Ok for master?
OK.
Thanks,
Richard.
> Thanks,
> Tamar
>
> gcc/ChangeLog:
>
> PR tree-optimization/113734
> * tree-vect-loop.cc (vect_transform_loop): Treat the final iteration of
> an early break loop as partial.
>
> gcc/testsuite/ChangeLog:
>
> PR tree-optimization/113734
> * gcc.dg/vect/vect-early-break_117-pr113734.c: New test.
>
> --- inline copy of patch --
> diff --git a/gcc/testsuite/gcc.dg/vect/vect-early-break_117-pr113734.c
> b/gcc/testsuite/gcc.dg/vect/vect-early-break_117-pr113734.c
> new file mode 100644
> index
> 0000000000000000000000000000000000000000..36ae09483dfd426f977a3d92cf24a78d76de6961
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/vect/vect-early-break_117-pr113734.c
> @@ -0,0 +1,37 @@
> +/* { dg-add-options vect_early_break } */
> +/* { dg-require-effective-target vect_early_break_hw } */
> +/* { dg-require-effective-target vect_int } */
> +/* { dg-additional-options "-O3" } */
> +
> +/* { dg-final { scan-tree-dump "LOOP VECTORIZED" "vect" } } */
> +
> +#include "tree-vect.h"
> +
> +#define N 306
> +#define NEEDLE 136
> +
> +int table[N];
> +
> +__attribute__ ((noipa))
> +int foo (int i, unsigned short parse_tables_n)
> +{
> + parse_tables_n >>= 9;
> + parse_tables_n += 11;
> + while (i < N && parse_tables_n--)
> + table[i++] = 0;
> +
> + return table[NEEDLE];
> +}
> +
> +int main ()
> +{
> + check_vect ();
> +
> + for (int j = 0; j < N; j++)
> + table[j] = -1;
> +
> + if (foo (0, 0xFFFF) != 0)
> + __builtin_abort ();
> +
> + return 0;
> +}
> diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
> index
> 854e9d78bc71721e6559a6bc5dff78c813603a78..0b1656fef2fed83f30295846c382ad9fb318454a
> 100644
> --- a/gcc/tree-vect-loop.cc
> +++ b/gcc/tree-vect-loop.cc
> @@ -12171,7 +12171,8 @@ vect_transform_loop (loop_vec_info loop_vinfo, gimple
> *loop_vectorized_call)
> /* True if the final iteration might not handle a full vector's
> worth of scalar iterations. */
> bool final_iter_may_be_partial
> - = LOOP_VINFO_USING_PARTIAL_VECTORS_P (loop_vinfo);
> + = LOOP_VINFO_USING_PARTIAL_VECTORS_P (loop_vinfo)
> + || LOOP_VINFO_EARLY_BREAKS (loop_vinfo);
> /* The minimum number of iterations performed by the epilogue. This
> is 1 when peeling for gaps because we always need a final scalar
> iteration. */
>
>
>
>
>
--
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)
