Re: [PATCH 0/4] bb-reorder: Add the "simple" algorithm

[Bernd Schmidt <bschmidt at redhat dot com>]

On 09/24/2015 12:06 AM, Segher Boessenkool wrote:
> The current basic block reordering always uses the "software trace cache"
> algorithm.  That has a few problems:
>
> 1) It increases code size substantially; this makes it not suitable for
> -O1 or -Os, and not at all for some architectures;
> 2) but it is enabled for -Os and all targets;
> 3) and -O1 gets nothing, resulting in pretty jumpy code.

A general question first, I see code in bb-reorder.c (in copy_bb_p) that 
limits the amount of code growth if not optimizing for speed. Is that 
not working as expected or not sufficient?

Your code looks like a nice clean algorithm so I have no objections to 
it (detailed comments to follow), but I want to make sure it is 
necessary to add it.


Bernd