On Sun, 15 Nov 2020, Jan Hubicka wrote:
> > See PR97840.
> Thanks,
> this is a false positive where we fail to discover that pointed-to type
> is empty on non-x86_64 targets. This is triggered by better alias
> analysis caused by non-escape discovery.
>
> While this is not a full fix (I hope someone with more experience on
> C++ types and warnings will set up) I think it may be useful to avoid
> warning on unused parameter.
>
> Bootstrapped/regtested x86_64-linux, OK?
OK.
> PR middle-end/97840
> * tree-ssa-uninit.c (maybe_warn_pass_by_reference): Update prototype;
> silence warning on EAF_UNUSED parameters.
> (warn_uninitialized_vars): Update.
> diff --git a/gcc/tree-ssa-uninit.c b/gcc/tree-ssa-uninit.c
> index f23514395e0..1e074793b02 100644
> --- a/gcc/tree-ssa-uninit.c
> +++ b/gcc/tree-ssa-uninit.c
> @@ -443,7 +443,7 @@ maybe_warn_operand (ao_ref &ref, gimple *stmt, tree lhs,
> tree rhs,
> access implying read access to those objects. */
>
> static void
> -maybe_warn_pass_by_reference (gimple *stmt, wlimits &wlims)
> +maybe_warn_pass_by_reference (gcall *stmt, wlimits &wlims)
> {
> if (!wlims.wmaybe_uninit)
> return;
> @@ -501,6 +501,10 @@ maybe_warn_pass_by_reference (gimple *stmt, wlimits
> &wlims)
> && !TYPE_READONLY (TREE_TYPE (argtype)))
> continue;
>
> + /* Ignore args we are not going to read from. */
> + if (gimple_call_arg_flags (stmt, argno - 1) & EAF_UNUSED)
> + continue;
> +
> if (save_always_executed && access->mode == access_read_only)
> /* Attribute read_only arguments imply read access. */
> wlims.always_executed = true;
> @@ -639,8 +643,8 @@ warn_uninitialized_vars (bool wmaybe_uninit)
> if (gimple_vdef (stmt))
> wlims.vdef_cnt++;
>
> - if (is_gimple_call (stmt))
> - maybe_warn_pass_by_reference (stmt, wlims);
> + if (gcall *call = dyn_cast <gcall *> (stmt))
> + maybe_warn_pass_by_reference (call, wlims);
> else if (gimple_assign_load_p (stmt)
> && gimple_has_location (stmt))
> {
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Felix Imend
