[Bug c/36359] New: [Regression] compile error in linux-kernel 2.6.26-rc4 with -O2

["mt-ml at gmx dot de" <gcc-bugzilla at gcc dot gnu dot org>]

Hi
I've tested gcc-4.4 with the current developer kernel 2.6.26-rc4 and got the
following compile error:

...
Setup is 12236 bytes (padded to 12288 bytes).
System is 2521 kB
CRC 735d1682
Kernel: arch/x86/boot/bzImage is ready  (#62)
  Building modules, stage 2.
  MODPOST 222 modules
ERROR: "____ilog2_NaN" [drivers/usb/core/usbcore.ko] undefined!
make[1]: *** [__modpost] Error 1
make: *** [modules] Error 2

This can be avoided when switching on the OPTIMIZE_SIZE kconfig option which in
fact replaces the standard -O2 option with -Os, so I think there must be
something wrong in what -O2 does. 
This happens only with gcc-4.4 not with gcc-4.3 and before (I've also tested
gcc-4.1). The latest gcc-4.4 version I tested was 20080526.

I compiled gcc without any options to ./configure.

I'll try to attach my config file so you might be able to reproduce the error.

This has been reported to lkml. The discussion can be read here:
http://lkml.org/lkml/2008/5/25/169.

Thanks
Mirco


-- 
           Summary: [Regression] compile error in linux-kernel 2.6.26-rc4
                    with -O2
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: mt-ml at gmx dot de
 GCC build triplet: none
  GCC host triplet: ubuntu linux 8.10 (dev)
GCC target triplet: x86_64


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36359