Ping (added some Cc:s).
Thanks in advance,
Segher
On Fri, Aug 07, 2020 at 09:51:04PM +0000, Segher Boessenkool wrote:
> When the compgotos pass copies the tail of blocks ending in an indirect
> jump, there is a micro-optimization to not copy the last one, since the
> original block will then just be deleted. This does not work properly
> if cleanup_cfg does not merge all pairs of blocks we expect it to.
>
>
> v2: This also deletes the other use of single_pred_p, which has the same
> problem in principle, I just never have triggered it so far.
>
> Tested on powerpc64-linux {-m32,-m64} like before. Is this okay for
> trunk?
>
>
> Segher
>
>
> 2020-08-07 Segher Boessenkool <seg...@kernel.crashing.org>
>
> PR rtl-optimization/96475
> * bb-reorder.c (maybe_duplicate_computed_goto): Remove single_pred_p
> micro-optimization.
> ---
> gcc/bb-reorder.c | 10 +++-------
> 1 file changed, 3 insertions(+), 7 deletions(-)
>
> diff --git a/gcc/bb-reorder.c b/gcc/bb-reorder.c
> index c635010..76e56b5 100644
> --- a/gcc/bb-reorder.c
> +++ b/gcc/bb-reorder.c
> @@ -2680,9 +2680,6 @@ make_pass_reorder_blocks (gcc::context *ctxt)
> static bool
> maybe_duplicate_computed_goto (basic_block bb, int max_size)
> {
> - if (single_pred_p (bb))
> - return false;
> -
> /* Make sure that the block is small enough. */
> rtx_insn *insn;
> FOR_BB_INSNS (bb, insn)
> @@ -2700,10 +2697,9 @@ maybe_duplicate_computed_goto (basic_block bb, int
> max_size)
> {
> basic_block pred = e->src;
>
> - /* Do not duplicate BB into PRED if that is the last predecessor, or if
> - we cannot merge a copy of BB with PRED. */
> - if (single_pred_p (bb)
> - || !single_succ_p (pred)
> + /* Do not duplicate BB into PRED if we cannot merge a copy of BB
> + with PRED. */
> + if (!single_succ_p (pred)
> || e->flags & EDGE_COMPLEX
> || pred->index < NUM_FIXED_BLOCKS
> || (JUMP_P (BB_END (pred)) && !simplejump_p (BB_END (pred)))
> --
> 1.8.3.1
