On Thu, 13 Jan 2022, Jakub Jelinek wrote:
> Hi!
>
> The following patch avoids emitting a parameter copy statement when inlining
> if the parameter has empty type. E.g. the gimplifier does something similar
> (except that it needs to evaluate side-effects if any, which isn't the case
> here):
> /* For empty types only gimplify the left hand side and right hand
> side as statements and throw away the assignment. Do this after
> gimplify_modify_expr_rhs so we handle TARGET_EXPRs of addressable
> types properly. */
> if (is_empty_type (TREE_TYPE (*from_p))
> && !want_value
> /* Don't do this for calls that return addressable types, expand_call
> relies on those having a lhs. */
> && !(TREE_ADDRESSABLE (TREE_TYPE (*from_p))
> && TREE_CODE (*from_p) == CALL_EXPR))
> {
> gimplify_stmt (from_p, pre_p);
> gimplify_stmt (to_p, pre_p);
> *expr_p = NULL_TREE;
> return GS_ALL_DONE;
> }
> Unfortunately, this patch doesn't cure the uninit warnings in that PR,
> but I think is desirable anyway.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
Hmm, but not emitting the initialization might cause even more such
warnings for the case where the passed in argument _is_ initialized
(or not visible as not, like when being a function parameter itself)?
Otherwise sure, it's the same what the gimplifier does.
I wonder if instead uninit warning should simply ignore uses of
"empty" typed variables?
OK.
Thanks,
Richard.
> 2022-01-13 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/103989
> * tree-inline.c (setup_one_parameter): Don't copy parms with
> empty type.
>
> --- gcc/tree-inline.c.jj 2022-01-11 23:11:23.422275652 +0100
> +++ gcc/tree-inline.c 2022-01-12 18:37:44.119950128 +0100
> @@ -3608,7 +3608,7 @@ setup_one_parameter (copy_body_data *id,
> init_stmt = gimple_build_assign (def, rhs);
> }
> }
> - else
> + else if (!is_empty_type (TREE_TYPE (var)))
> init_stmt = gimple_build_assign (var, rhs);
>
> if (bb && init_stmt)
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Ivo Totev; HRB 36809 (AG Nuernberg)
