[Bug rtl-optimization/69609] block reordering consumes an inordinate amount of time, REE consumes much memory

[dcb314 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69609

--- Comment #7 from David Binderman <dcb314 at hotmail dot com> ---
(In reply to Richard Biener from comment #6)
> Maybe sth as simple as
> 
> Index: gcc/bb-reorder.c
> ===================================================================
> --- gcc/bb-reorder.c    (revision 233262)
> +++ gcc/bb-reorder.c    (working copy)
> @@ -889,6 +889,7 @@ bb_to_key (basic_block bb)
>  
>    /* Prefer blocks whose predecessor is an end of some trace
>       or whose predecessor edge is EDGE_DFS_BACK.  */
> +  if (EDGE_COUNT (bb->preds) <= 8)
>    FOR_EACH_EDGE (e, ei, bb->preds)
>      {
>        if ((e->src != ENTRY_BLOCK_PTR_FOR_FN (cfun)
> 
> or precomputing whether a BB has abnormal preds and disabling the trace in
> that case (or somehow sorting the edge vectors so that abnormal edges
> come last so we can stop at the first abnormal edge).

I tried this patch and it changes compile time from something
more than ten minutes to 1m57s.

More than five times faster looks good to go to me.