On Wed, Mar 27, 2024 at 04:42:21PM +0100, Richard Biener wrote:
> PR middle-end/114480
> * cfganal.cc (compute_idf): Use simpler bitmap iteration,
> touch work_set only when phi_insertion_points changed.
> ---
> gcc/cfganal.cc | 10 +++-------
> 1 file changed, 3 insertions(+), 7 deletions(-)
>
> diff --git a/gcc/cfganal.cc b/gcc/cfganal.cc
> index 432775decf1..5ef629f677e 100644
> --- a/gcc/cfganal.cc
> +++ b/gcc/cfganal.cc
> @@ -1701,8 +1701,7 @@ compute_idf (bitmap def_blocks, bitmap_head *dfs)
> on earlier blocks first is better.
> ??? Basic blocks are by no means guaranteed to be ordered in
> optimal order for this iteration. */
> - bb_index = bitmap_first_set_bit (work_set);
> - bitmap_clear_bit (work_set, bb_index);
> + bb_index = bitmap_clear_first_set_bit (work_set);
>
> /* Since the registration of NEW -> OLD name mappings is done
> separately from the call to update_ssa, when updating the SSA
The above is clearly obvious.
> @@ -1712,12 +1711,9 @@ compute_idf (bitmap def_blocks, bitmap_head *dfs)
> gcc_checking_assert (bb_index
> < (unsigned) last_basic_block_for_fn (cfun));
>
> - EXECUTE_IF_AND_COMPL_IN_BITMAP (&dfs[bb_index], phi_insertion_points,
> - 0, i, bi)
> - {
> + EXECUTE_IF_SET_IN_BITMAP (&dfs[bb_index], 0, i, bi)
> + if (bitmap_set_bit (phi_insertion_points, i))
> bitmap_set_bit (work_set, i);
> - bitmap_set_bit (phi_insertion_points, i);
> - }
> }
I don't understand why the above is better.
Wouldn't it be best to do
bitmap_ior_and_compl_into (work_set, &dfs[bb_index],
phi_insertion_points);
bitmap_ior_into (phi_insertion_points, &dfs[bb_index]);
?
Jakub
