Today's (2008-02-06) gcc-trunk (rev 132144) fails to build rtems.

Seemingly it generates invalid assembly code:

# i386-rtems4.9-gcc --pipe  -mtune=pentiumpro --pipe -DHAVE_CONFIG_H   -I.. -I../../../lib/include -I../../../../../../rtems.orig/cpukit/libnetworking -D_COMPILING_BSD_KERNEL_ -DKERNEL -DINET -DNFS -DDIAGNOSTIC -DBOOTP_COMPAT -D_KERNEL -D__BSD_VISIBLE  -Wall -fasm -g -O2 -MT netinet/libnetworking_a-in_cksum.o -MD -MP -MF netinet/.deps/libnetworking_a-in_cksum.Tpo -c -o netinet/libnetworking_a-in_cksum.o `test -f 'netinet/in_cksum.c' || echo '../../../../../../rtems.orig/cpukit/libnetworking/'`netinet/in_cksum.c
{standard input}: Assembler messages:
{standard input}:947: Error: bad register name `%sil'
gmake[2]: *** [netinet/libnetworking_a-in_cksum.o] Error 1

# i386-rtems4.9-as --version
GNU assembler (GNU Binutils) 2.18

The same piece of code builds fine with gcc-4.2.3