Richard Biener <rguent...@suse.de> writes:
> The following removes an optimization that wrongly triggers right now
> because it accesses LOOP_VINFO_COST_MODEL_THRESHOLD which might not be
> computed yet.
>
> Testing on x86_64 didn't reveal any testsuite coverage.
>
> Bootstrapped and tested on x86_64-unknown-linux-gnu.
>
> OK?
>
> PR tree-optimization/120939
> * tree-vect-loop.cc (vect_need_peeling_or_partial_vectors_p):
> Remove eliding an epilogue based on not computed
> LOOP_VINFO_COST_MODEL_THRESHOLD.
This regresses:
FAIL: gcc.dg/torture/pr113026-1.c -O3 -fomit-frame-pointer -funroll-loops
-fpeel-loops -ftracer -finline-functions (test for bogus messages, line 10)
on aarch64-linux-gnu, with:
.../pr113026-1.c:10:12: warning: writing 1 byte into a region of size 0
[-Wstringop-overflow=]
.../pr113026-1.c:4:6: note: at offset 16 into destination object 'dst' of size
16
I haven't looked into why yet, but it does seem superficially similar
to PR60505, which was what this code seems to have been added to fix
(g:090cd8dc70b80183c83d9f43f1e6ab9970481efd).
Thanks,
Richard
> ---
> gcc/tree-vect-loop.cc | 21 ++-------------------
> 1 file changed, 2 insertions(+), 19 deletions(-)
>
> diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
> index 46a6399243d..7ac61d4dce2 100644
> --- a/gcc/tree-vect-loop.cc
> +++ b/gcc/tree-vect-loop.cc
> @@ -1224,13 +1224,6 @@ static bool
> vect_need_peeling_or_partial_vectors_p (loop_vec_info loop_vinfo)
> {
> unsigned HOST_WIDE_INT const_vf;
> - HOST_WIDE_INT max_niter
> - = likely_max_stmt_executions_int (LOOP_VINFO_LOOP (loop_vinfo));
> -
> - unsigned th = LOOP_VINFO_COST_MODEL_THRESHOLD (loop_vinfo);
> - if (!th && LOOP_VINFO_ORIG_LOOP_INFO (loop_vinfo))
> - th = LOOP_VINFO_COST_MODEL_THRESHOLD (LOOP_VINFO_ORIG_LOOP_INFO
> - (loop_vinfo));
>
> if (LOOP_VINFO_NITERS_KNOWN_P (loop_vinfo)
> && LOOP_VINFO_PEELING_FOR_ALIGNMENT (loop_vinfo) >= 0)
> @@ -1250,18 +1243,8 @@ vect_need_peeling_or_partial_vectors_p (loop_vec_info
> loop_vinfo)
> VF * N + 1. That's something of a niche case though. */
> || LOOP_VINFO_PEELING_FOR_GAPS (loop_vinfo)
> || !LOOP_VINFO_VECT_FACTOR (loop_vinfo).is_constant (&const_vf)
> - || ((tree_ctz (LOOP_VINFO_NITERS (loop_vinfo))
> - < (unsigned) exact_log2 (const_vf))
> - /* In case of versioning, check if the maximum number of
> - iterations is greater than th. If they are identical,
> - the epilogue is unnecessary. */
> - && (!LOOP_REQUIRES_VERSIONING (loop_vinfo)
> - || ((unsigned HOST_WIDE_INT) max_niter
> - /* We'd like to use LOOP_VINFO_VERSIONING_THRESHOLD
> - but that's only computed later based on our result.
> - The following is the most conservative approximation. */
> - > (std::max ((unsigned HOST_WIDE_INT) th,
> - const_vf) / const_vf) * const_vf))))
> + || (tree_ctz (LOOP_VINFO_NITERS (loop_vinfo))
> + < (unsigned) exact_log2 (const_vf)))
> return true;
>
> return false;
