On Mon, 18 Dec 2017, Jakub Jelinek wrote:
> Hi!
>
> When backporting the wrong-code bugfix parts of PR80631 to 7.3, I've noticed
> that we perform the optimization to use the induc_val only when reduc_fn is
> IFN_REDUC_{MAX,MIN}. That is true e.g. for AVX2, but not plain SSE2, so if
> we have a loop like:
> void foo (int *v)
> {
> int found_index = -17;
> for (int k = 0; k < 64; k++)
> if (v[k] == 77)
> found_index = k;
> return found_index;
> }
> we start with { -17, -17, -17... } only for avx* and can optimize away
> the scalar if (reduc_result == -17 ? -17 : reduc_result, but for sse*
> we start instead with { -1, -1, -1... } and can't optimize
> if (reduc_result == -1 ? -17 : reduc_result.
>
> Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
> trunk?
Ok.
> 2017-12-18 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/80631
> * tree-vect-loop.c (vect_create_epilog_for_reduction): Compare
> induc_code against MAX_EXPR or MIN_EXPR instead of reduc_fn against
> IFN_REDUC_MAX or IFN_REDUC_MIN.
>
> --- gcc/tree-vect-loop.c.jj 2017-12-12 09:54:28.000000000 +0100
> +++ gcc/tree-vect-loop.c 2017-12-15 18:56:15.426591727 +0100
> @@ -4432,9 +4432,9 @@ vect_create_epilog_for_reduction (vec<tr
> && (STMT_VINFO_VEC_REDUCTION_TYPE (stmt_info)
> == INTEGER_INDUC_COND_REDUCTION)
> && !integer_zerop (induc_val)
> - && ((reduc_fn == IFN_REDUC_MAX
> + && ((induc_code == MAX_EXPR
> && tree_int_cst_lt (initial_def, induc_val))
> - || (reduc_fn == IFN_REDUC_MIN
> + || (induc_code == MIN_EXPR
> && tree_int_cst_lt (induc_val, initial_def))))
> induc_val = initial_def;
> vect_is_simple_use (initial_def, loop_vinfo, &def_stmt,
> &initial_def_dt);
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
