On Tue, 16 Nov 2021, Tamar Christina wrote:
> Hi All,
>
> convert_mult_to_fma assumes that all gimple_assigns have a LHS set. This
> assumption is however not true when an IFN is kept around just for the
> side-effects. In those situations you have just the IFN and lhs will be null.
>
> Since there's no LHS, there also can't be any ADD and such it can't be an FMA
> so it's correct to just return early if no LHS.
>
> Bootstrapped Regtested on aarch64-none-linux-gnu,
> x86_64-pc-linux-gnu and no regressions.
>
> Ok for master?
OK.
Thanks,
Richard.
> Thanks,
> Tamar
>
>
>
> gcc/ChangeLog:
>
> PR tree-optimizations/103253
> * tree-ssa-math-opts.c (convert_mult_to_fma): Check for LHS.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.dg/vect/pr103253.c: New test.
>
> --- inline copy of patch --
> diff --git a/gcc/testsuite/gcc.dg/vect/pr103253.c
> b/gcc/testsuite/gcc.dg/vect/pr103253.c
> new file mode 100644
> index
> 0000000000000000000000000000000000000000..abe3f09f3818d79a53f2aa962c6b6c06855d618e
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/vect/pr103253.c
> @@ -0,0 +1,16 @@
> +/* { dg-do compile } */
> +/* { dg-require-effective-target fopenmp } */
> +/* { dg-additional-options "-O2 -fexceptions -fopenmp
> -fno-delete-dead-exceptions -fno-trapping-math" } */
> +
> +double
> +do_work (double do_work_pri)
> +{
> + int i;
> +
> +#pragma omp simd
> + for (i = 0; i < 17; ++i)
> + do_work_pri = (!i ? 0.5 : i) * 2.0;
> +
> + return do_work_pri;
> +}
> +
> diff --git a/gcc/tree-ssa-math-opts.c b/gcc/tree-ssa-math-opts.c
> index
> c4a6492b50df25b4cf296a75bd51e5af34eeacc7..cc8496c3c325f3cc303a90b9b9cac383e5a7942d
> 100644
> --- a/gcc/tree-ssa-math-opts.c
> +++ b/gcc/tree-ssa-math-opts.c
> @@ -3224,6 +3224,10 @@ convert_mult_to_fma (gimple *mul_stmt, tree op1, tree
> op2,
> fma_deferring_state *state, tree mul_cond = NULL_TREE)
> {
> tree mul_result = gimple_get_lhs (mul_stmt);
> + /* If there isn't a LHS then this can't be an FMA. There can be no LHS
> + if the statement was left just for the side-effects. */
> + if (!mul_result)
> + return false;
> tree type = TREE_TYPE (mul_result);
> gimple *use_stmt, *neguse_stmt;
> use_operand_p use_p;
>
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Ivo Totev; HRB 36809 (AG Nuernberg)
