On Wed, Nov 14, 2018 at 3:51 PM Michael Matz <m...@suse.de> wrote:
>
> Hi,
>
> our warning code sometimes adds locations to statement which didn't have
> them before, which can in turn lead to code changes (here only label
> numbers change). It seems better to not do that from warning code, and
> here it's easy to do: just return the location we want to use for
> warnings, don't change it in the statement itself.
>
> Regstrapped on x86-64, okay for trunk?
OK.
Richard.
>
> Ciao,
> Michael.
>
> PR middle-end/86575
> * gimplify.c (collect_fallthrough_labels): Add new argument,
> return location via that, don't modify statements.
> (warn_implicit_fallthrough_r): Adjust call, don't use
> statement location directly.
>
> diff --git a/gcc/gimplify.c b/gcc/gimplify.c
> index 509fc2f3f5be..22dff0e546c9 100644
> --- a/gcc/gimplify.c
> +++ b/gcc/gimplify.c
> @@ -1938,10 +1938,12 @@ last_stmt_in_scope (gimple *stmt)
>
> static gimple *
> collect_fallthrough_labels (gimple_stmt_iterator *gsi_p,
> - auto_vec <struct label_entry> *labels)
> + auto_vec <struct label_entry> *labels,
> + location_t *prevloc)
> {
> gimple *prev = NULL;
>
> + *prevloc = UNKNOWN_LOCATION;
> do
> {
> if (gimple_code (gsi_stmt (*gsi_p)) == GIMPLE_BIND)
> @@ -1978,7 +1980,7 @@ collect_fallthrough_labels (gimple_stmt_iterator *gsi_p,
> /* It might be a label without a location. Use the
> location of the scope then. */
> if (!gimple_has_location (prev))
> - gimple_set_location (prev, bind_loc);
> + *prevloc = bind_loc;
> }
> gsi_next (gsi_p);
> continue;
> @@ -2061,6 +2063,8 @@ collect_fallthrough_labels (gimple_stmt_iterator *gsi_p,
> && (gimple_code (gsi_stmt (*gsi_p)) != GIMPLE_LABEL
> || !gimple_has_location (gsi_stmt (*gsi_p))));
>
> + if (prev && gimple_has_location (prev))
> + *prevloc = gimple_location (prev);
> return prev;
> }
>
> @@ -2157,7 +2161,8 @@ warn_implicit_fallthrough_r (gimple_stmt_iterator
> *gsi_p, bool *handled_ops_p,
>
> /* Vector of labels that fall through. */
> auto_vec <struct label_entry> labels;
> - gimple *prev = collect_fallthrough_labels (gsi_p, &labels);
> + location_t prevloc;
> + gimple *prev = collect_fallthrough_labels (gsi_p, &labels, &prevloc);
>
> /* There might be no more statements. */
> if (gsi_end_p (*gsi_p))
> @@ -2185,8 +2190,8 @@ warn_implicit_fallthrough_r (gimple_stmt_iterator
> *gsi_p, bool *handled_ops_p,
> /* Try to be clever and don't warn when the statement
> can't actually fall through. */
> && gimple_stmt_may_fallthru (prev)
> - && gimple_has_location (prev))
> - warned_p = warning_at (gimple_location (prev),
> + && prevloc != UNKNOWN_LOCATION)
> + warned_p = warning_at (prevloc,
> OPT_Wimplicit_fallthrough_,
> "this statement may fall through");
> if (warned_p)
