On Wed, Nov 10, 2021 at 12:16 AM Jason Merrill <ja...@redhat.com> wrote:
>
> On 11/9/21 13:42, Patrick Palka wrote:
> > On Tue, 9 Nov 2021, Jason Merrill wrote:
> >
> >> On 11/9/21 11:02, Patrick Palka wrote:
> >>> Bootstrapped and regtested on x86_64-pc-linux-gnu, OK for trunk?
> >>
> >> OK, though I wonder about using releasing_vec instead of auto_vec; reusing
> >> a
> >> previously allocated vec vs. building one on the stack.
> >
> > Thanks a lot. And hmm, I think using reusing a previously allocated vec
> > here would be tricky since cp_parser_template_argument_list can be
> > called recursively, and so only the outermost call would be able to
> > benefit from reuse unless we perhaps maintain a freelist of such vecs
> > IIUC.
>
> We do maintain such a freelist, in make_tree_vector/release_tree_vector,
> which releasing_vec is a wrapper class for.
Oops sorry, I had totally forgotten about that aspect of
make/release_tree_vector. Hmm, so given that a template argument list
is very likely to be very small, whereas a vector obtained from the
freelist can have an arbitrary large capacity (depending on what it
stored for its previous users), it seems more overall resourceful to
use a stack-allocated auto_vec here IMHO.
>
> > Seems like that would complicate the code enough to not be worth
> > it.
> >
> >>> gcc/cp/ChangeLog:
> >>>
> >>> * parser.c (cp_parser_template_argument_list): Use auto_vec
> >>> instead of manual memory management.
> >>> ---
> >>> gcc/cp/parser.c | 35 ++++++++---------------------------
> >>> 1 file changed, 8 insertions(+), 27 deletions(-)
> >>>
> >>> diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
> >>> index 32de97b08bd..8823399529e 100644
> >>> --- a/gcc/cp/parser.c
> >>> +++ b/gcc/cp/parser.c
> >>> @@ -18558,11 +18558,6 @@ cp_parser_template_name (cp_parser* parser,
> >>> static tree
> >>> cp_parser_template_argument_list (cp_parser* parser)
> >>> {
> >>> - tree fixed_args[10];
> >>> - unsigned n_args = 0;
> >>> - unsigned alloced = 10;
> >>> - tree *arg_ary = fixed_args;
> >>> - tree vec;
> >>> bool saved_in_template_argument_list_p;
> >>> bool saved_ice_p;
> >>> bool saved_non_ice_p;
> >>> @@ -18581,16 +18576,15 @@ cp_parser_template_argument_list (cp_parser*
> >>> parser)
> >>> parser->non_integral_constant_expression_p = false;
> >>> /* Parse the arguments. */
> >>> + auto_vec<tree, 10> args;
> >>> do
> >>> {
> >>> - tree argument;
> >>> -
> >>> - if (n_args)
> >>> + if (!args.is_empty ())
> >>> /* Consume the comma. */
> >>> cp_lexer_consume_token (parser->lexer);
> >>> /* Parse the template-argument. */
> >>> - argument = cp_parser_template_argument (parser);
> >>> + tree argument = cp_parser_template_argument (parser);
> >>> /* If the next token is an ellipsis, we're expanding a template
> >>> argument pack. */
> >>> @@ -18610,29 +18604,16 @@ cp_parser_template_argument_list (cp_parser*
> >>> parser)
> >>> argument = make_pack_expansion (argument);
> >>> }
> >>> - if (n_args == alloced)
> >>> - {
> >>> - alloced *= 2;
> >>> -
> >>> - if (arg_ary == fixed_args)
> >>> - {
> >>> - arg_ary = XNEWVEC (tree, alloced);
> >>> - memcpy (arg_ary, fixed_args, sizeof (tree) * n_args);
> >>> - }
> >>> - else
> >>> - arg_ary = XRESIZEVEC (tree, arg_ary, alloced);
> >>> - }
> >>> - arg_ary[n_args++] = argument;
> >>> + args.safe_push (argument);
> >>> }
> >>> while (cp_lexer_next_token_is (parser->lexer, CPP_COMMA));
> >>> - vec = make_tree_vec (n_args);
> >>> + int n_args = args.length ();
> >>> + tree vec = make_tree_vec (n_args);
> >>> - while (n_args--)
> >>> - TREE_VEC_ELT (vec, n_args) = arg_ary[n_args];
> >>> + for (int i = 0; i < n_args; i++)
> >>> + TREE_VEC_ELT (vec, i) = args[i];
> >>> - if (arg_ary != fixed_args)
> >>> - free (arg_ary);
> >>> parser->non_integral_constant_expression_p = saved_non_ice_p;
> >>> parser->integral_constant_expression_p = saved_ice_p;
> >>> parser->in_template_argument_list_p =
> >>> saved_in_template_argument_list_p;
> >>>
> >>
> >>
> >
>
