[Bug rtl-optimization/67864] [6 Regression] CSiBE size regression

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67864

--- Comment #1 from Segher Boessenkool <segher at gcc dot gnu.org> ---
Author: segher
Date: Sun Oct 11 09:03:09 2015
New Revision: 228692

URL: https://gcc.gnu.org/viewcvs?rev=228692&root=gcc&view=rev
Log:
bb-reorder: Improve the simple algorithm for -Os (PR67864)

As the PR points out, the "simple" reorder algorithm makes bigger code
than the STC algorithm did, for -Os, for x86.  I now tested it for many
different targets and it turns out to be worse everywhere.

This simple patch tunes "simple" a bit; this makes it better than STC
almost everywhere.  The only exceptions (for the targets where I have
results) are x86 and mn10300.  For those targets it may be best to switch
the default algorithm for -Os to STC.


2015-10-11  Segher Boessenkool  <segher@kernel.crashing.org>

        PR rtl-optimization/67864
        * gcc/bb-reorder (reorder_basic_blocks_simple): Prefer existing
        fallthrough edges for conditional jumps.  Don't sort candidate
        edges if not optimizing for speed.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/bb-reorder.c