[Bug rtl-optimization/53595] New: Code size increase of +10% between two 4.7.1 snapshot

["gjl at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53595

             Bug #: 53595
           Summary: Code size increase of +10% between two 4.7.1 snapshot
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: gjl@gcc.gnu.org


Created attachment 27568
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27568
C source

This problem report is about a +10% of code size increase between the following
two 4.7.1 versions of gcc:

V1: SVN 185693 gcc-4_7-branch from 2012-03-22, 4.7.1 (prerelease)
V2: SVN 188257 gcc-4_7-branch from 2012-06-06, 4.7.1 (prerelease)

The attached test case is a reduced test case out of many other sources that
suffer from the same problem, so that the overall performance degradation is
unpleasant.

The RTL dumps show that the first pass that differs is IRA.

== Command line ==

$ avr-gcc -mmcu=atmega168 -c -std=gnu99 -Os -mstrict-X -ffixed-2 -ffixed-3 -dp
-fdump-rtl-ira-details -fdump-rtl-reload-details -fdump-rtl-postreload-details
bresenham-i.c -o bresenham-i-1.o -save-temps=obj

resp. with  -o bresenham-i-2.o for the second 4.7.1 snapshot.

== GCC configure ==

Target: avr
Configured with: ../../gcc.gnu.org/gcc-4_7-branch/configure --target=avr
--prefix=/local/gnu/install/gcc-4.7-mingw32 --host=i386-mingw32
--build=i686-linux-gnu --enable-languages=c,c++ --disable-nls --disable-shared
--with-dwarf2
Thread model: single
gcc version 4.7.1 20120606 (prerelease) (GCC) 

GNU C (GCC) version 4.7.1 20120606 (prerelease) (avr)
    compiled by GNU C version 3.4.5 (mingw-vista special r2), GMP version
4.3.2, MPFR version 2.4.2, MPC version 0.8.2

It's a canadian cross, but that surely does not matter here...