[PATCH 3/3] vec: use inexact growth where possible.

[Richard Biener]

On Wed, Aug 26, 2020 at 11:02 PM Jeff Law <law@redhat.com> wrote:
>
> On Tue, 2020-08-11 at 13:37 +0200, Martin Liška wrote:
> > From cc1d41a469d76f2f8e4f44bed788ace77a1c6d62 Mon Sep 17 00:00:00 2001
> > From: Martin Liska <mliska@suse.cz>
> > Date: Mon, 10 Aug 2020 12:09:19 +0200
> > Subject: [PATCH 3/3] vec: use inexact growth where possible.
> >
> > gcc/ChangeLog:
> >
> >       * cfgrtl.c (rtl_create_basic_block): Use default value for
> >       growth vector function.
> >       * gimple.c (gimple_set_bb): Likewise.
> >       * symbol-summary.h: Likewise.
> >       * tree-cfg.c (init_empty_tree_cfg_for_function): Likewise.
> >       (build_gimple_cfg): Likewise.
> >       (create_bb): Likewise.
> >       (move_block_to_fn): Likewise.
> I'll note that in some cases we were avoiding exponential growth in our new size
> computations.  Presumably the inexact growth support will do something similar,
> even if it's not exactly the same.  Right?  Assuming that's the case this is OK
> too.

@@ -183,12 +183,12 @@ init_empty_tree_cfg_for_function (struct function *fn)
   last_basic_block_for_fn (fn) = NUM_FIXED_BLOCKS;
   vec_alloc (basic_block_info_for_fn (fn), initial_cfg_capacity);
   vec_safe_grow_cleared (basic_block_info_for_fn (fn),
-                        initial_cfg_capacity, true);
+                        initial_cfg_capacity);

   /* Build a mapping of labels to their associated blocks.  */
   vec_alloc (label_to_block_map_for_fn (fn), initial_cfg_capacity);
   vec_safe_grow_cleared (label_to_block_map_for_fn (fn),
-                        initial_cfg_capacity, true);
+                        initial_cfg_capacity);

this is odd now at least since we explicitely alloc initial_cfg_capacity.
IMHO we should instead use

 basic_block_info_for_fn (fn)->quick_grow_cleared (initial_cfg_capacity)

here?

The rest looks OK and along the plan.

Thanks,
Richard.

> jeff
>