On Tue, 1 Mar 2022, H.J. Lu wrote:
> Use C++ RAII with make_temp_override in the C++ FE to automatically clear
> currently_expanding_gimple_stmt.
Hmm, the temp-override isn't really a good fit since we only want to
have the cleanup part and that should always "restore" to nullptr.
Richard.
> gcc/
>
> PR middle-end/104721
> * cfgexpand.cc (expand_gimple_basic_block): Use make_temp_override
> to clear currently_expanding_gimple_stmt automatically.
> * tree.h (temp_override): Moved from cp/cp-tree.h.
> (type_identity_t): Likewise.
> make_temp_override(): Likewise.
>
> gcc/cp/
>
> PR middle-end/104721
> * cp-tree.h (temp_override): Moved to ../tree.h.
> (type_identity_t): Likewise.
> make_temp_override(): Likewise.
> ---
> gcc/cfgexpand.cc | 15 +++++---------
> gcc/cp/cp-tree.h | 51 ------------------------------------------------
> gcc/tree.h | 51 ++++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 56 insertions(+), 61 deletions(-)
>
> diff --git a/gcc/cfgexpand.cc b/gcc/cfgexpand.cc
> index 87536ec7ccd..3d656113df5 100644
> --- a/gcc/cfgexpand.cc
> +++ b/gcc/cfgexpand.cc
> @@ -5817,6 +5817,9 @@ expand_gimple_basic_block (basic_block bb, bool
> disable_tail_calls)
> if (note)
> NOTE_BASIC_BLOCK (note) = bb;
>
> + auto cleanup = make_temp_override (currently_expanding_gimple_stmt,
> + nullptr);
> +
> for (; !gsi_end_p (gsi); gsi_next (&gsi))
> {
> basic_block new_bb;
> @@ -5927,10 +5930,7 @@ expand_gimple_basic_block (basic_block bb, bool
> disable_tail_calls)
> {
> new_bb = expand_gimple_cond (bb, as_a <gcond *> (stmt));
> if (new_bb)
> - {
> - currently_expanding_gimple_stmt = NULL;
> - return new_bb;
> - }
> + return new_bb;
> }
> else if (is_gimple_debug (stmt))
> {
> @@ -6052,10 +6052,7 @@ expand_gimple_basic_block (basic_block bb, bool
> disable_tail_calls)
> if (can_fallthru)
> bb = new_bb;
> else
> - {
> - currently_expanding_gimple_stmt = NULL;
> - return new_bb;
> - }
> + return new_bb;
> }
> }
> else
> @@ -6078,8 +6075,6 @@ expand_gimple_basic_block (basic_block bb, bool
> disable_tail_calls)
> }
> }
>
> - currently_expanding_gimple_stmt = NULL;
> -
> /* Expand implicit goto and convert goto_locus. */
> FOR_EACH_EDGE (e, ei, bb->succs)
> {
> diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
> index 80994e94793..0a55588dc5d 100644
> --- a/gcc/cp/cp-tree.h
> +++ b/gcc/cp/cp-tree.h
> @@ -1961,57 +1961,6 @@ public:
> }
> };
>
> -/* RAII sentinel that saves the value of a variable, optionally
> - overrides it right away, and restores its value when the sentinel
> - id destructed. */
> -
> -template <typename T>
> -class temp_override
> -{
> - T& overridden_variable;
> - T saved_value;
> -public:
> - temp_override(T& var) : overridden_variable (var), saved_value (var) {}
> - temp_override(T& var, T overrider)
> - : overridden_variable (var), saved_value (var)
> - {
> - overridden_variable = overrider;
> - }
> - ~temp_override() { overridden_variable = saved_value; }
> -};
> -
> -/* Wrapping a template parameter in type_identity_t hides it from template
> - argument deduction. */
> -#if __cpp_lib_type_identity
> -using std::type_identity_t;
> -#else
> -template <typename T>
> -struct type_identity { typedef T type; };
> -template <typename T>
> -using type_identity_t = typename type_identity<T>::type;
> -#endif
> -
> -/* Object generator function for temp_override, so you don't need to write
> the
> - type of the object as a template argument.
> -
> - Use as auto x = make_temp_override (flag); */
> -
> -template <typename T>
> -inline temp_override<T>
> -make_temp_override (T& var)
> -{
> - return { var };
> -}
> -
> -/* Likewise, but use as auto x = make_temp_override (flag, value); */
> -
> -template <typename T>
> -inline temp_override<T>
> -make_temp_override (T& var, type_identity_t<T> overrider)
> -{
> - return { var, overrider };
> -}
> -
> /* The cached class binding level, from the most recently exited
> class, or NULL if none. */
>
> diff --git a/gcc/tree.h b/gcc/tree.h
> index 36ceed57064..32d610474d2 100644
> --- a/gcc/tree.h
> +++ b/gcc/tree.h
> @@ -6581,4 +6581,55 @@ extern tree get_attr_nonstring_decl (tree, tree * =
> NULL);
>
> extern int get_target_clone_attr_len (tree);
>
> +/* RAII sentinel that saves the value of a variable, optionally
> + overrides it right away, and restores its value when the sentinel
> + id destructed. */
> +
> +template <typename T>
> +class temp_override
> +{
> + T& overridden_variable;
> + T saved_value;
> +public:
> + temp_override(T& var) : overridden_variable (var), saved_value (var) {}
> + temp_override(T& var, T overrider)
> + : overridden_variable (var), saved_value (var)
> + {
> + overridden_variable = overrider;
> + }
> + ~temp_override() { overridden_variable = saved_value; }
> +};
> +
> +/* Wrapping a template parameter in type_identity_t hides it from template
> + argument deduction. */
> +#if __cpp_lib_type_identity
> +using std::type_identity_t;
> +#else
> +template <typename T>
> +struct type_identity { typedef T type; };
> +template <typename T>
> +using type_identity_t = typename type_identity<T>::type;
> +#endif
> +
> +/* Object generator function for temp_override, so you don't need to write
> the
> + type of the object as a template argument.
> +
> + Use as auto x = make_temp_override (flag); */
> +
> +template <typename T>
> +inline temp_override<T>
> +make_temp_override (T& var)
> +{
> + return { var };
> +}
> +
> +/* Likewise, but use as auto x = make_temp_override (flag, value); */
> +
> +template <typename T>
> +inline temp_override<T>
> +make_temp_override (T& var, type_identity_t<T> overrider)
> +{
> + return { var, overrider };
> +}
> +
> #endif /* GCC_TREE_H */
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Ivo Totev; HRB 36809 (AG Nuernberg)
