On Tue, 7 Mar 2017, Jakub Jelinek wrote:
> Hi!
>
> If any of the operands of the UBSAN_{ADD,SUB,MUL}_OVERFLOW ifn with
> vector operand is a uniform vector, expanding it as VCE on the VECTOR_CST
> followed by ARRAY_REF with variable index in the loop is unnecessarily
> expensive and nothing fixes it afterwards.
> This works around ICE on s390 at least for the uniform vectors.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
Ok. Note that another option for the loopy case is to do
for (;;)
{
vec >> by-one-elt;
elt = BIT_FIELD_REF <vec, index-zero>;
}
when whole-vector shifts are available (they are constructed by
VEC_PERM_EXPR if vec_perm_const_ok for that mask). If you end up
doing variable-index array accesses you can as well spill the
vector to memory and use memory accesses on that. Not sure how
to arrange that from this part of the expander.
Unsure what the ICE you see with s390 is about...
Thanks,
Richard.
> 2017-03-07 Jakub Jelinek <ja...@redhat.com>
>
> PR sanitizer/79904
> * internal-fn.c (expand_vector_ubsan_overflow): If arg0 or arg1
> is a uniform vector, use uniform_vector_p return value instead of
> building ARRAY_REF on folded VIEW_CONVERT_EXPR to array type.
>
> * gcc.dg/ubsan/pr79904.c: New test.
>
> --- gcc/internal-fn.c.jj 2017-02-23 08:48:40.000000000 +0100
> +++ gcc/internal-fn.c 2017-03-07 11:55:56.261465702 +0100
> @@ -1869,12 +1869,20 @@ expand_vector_ubsan_overflow (location_t
> if (cnt > 4)
> {
> tree atype = build_array_type_nelts (eltype, cnt);
> - op0 = fold_build1_loc (loc, VIEW_CONVERT_EXPR, atype, arg0);
> - op0 = build4_loc (loc, ARRAY_REF, eltype, op0, cntv,
> - NULL_TREE, NULL_TREE);
> - op1 = fold_build1_loc (loc, VIEW_CONVERT_EXPR, atype, arg1);
> - op1 = build4_loc (loc, ARRAY_REF, eltype, op1, cntv,
> - NULL_TREE, NULL_TREE);
> + op0 = uniform_vector_p (arg0);
> + if (op0 == NULL_TREE)
> + {
> + op0 = fold_build1_loc (loc, VIEW_CONVERT_EXPR, atype, arg0);
> + op0 = build4_loc (loc, ARRAY_REF, eltype, op0, cntv,
> + NULL_TREE, NULL_TREE);
> + }
> + op1 = uniform_vector_p (arg1);
> + if (op1 == NULL_TREE)
> + {
> + op1 = fold_build1_loc (loc, VIEW_CONVERT_EXPR, atype, arg1);
> + op1 = build4_loc (loc, ARRAY_REF, eltype, op1, cntv,
> + NULL_TREE, NULL_TREE);
> + }
> if (resv)
> {
> res = fold_build1_loc (loc, VIEW_CONVERT_EXPR, atype, resv);
> --- gcc/testsuite/gcc.dg/ubsan/pr79904.c.jj 2017-03-07 11:58:53.266120958
> +0100
> +++ gcc/testsuite/gcc.dg/ubsan/pr79904.c 2017-03-07 11:58:46.000000000
> +0100
> @@ -0,0 +1,11 @@
> +/* PR sanitizer/79904 */
> +/* { dg-do compile } */
> +/* { dg-options "-fsanitize=signed-integer-overflow -Wno-psabi" } */
> +
> +typedef signed char V __attribute__((vector_size (8)));
> +
> +void
> +foo (V *a)
> +{
> + *a = *a * 3;
> +}
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
