Building for a target of win64 on cygwin results in an ICE while building the crt for the toolchain.  Using this sequence:

binutils
all-gcc
crt
gcc

The crt phase dies as follows:

x86_64-pc-mingw32-gcc -DHAVE_CONFIG_H -I. -I/var/lib/buildbot/slave-vista64-cyg32/cygwin-x86/build/mingw/obj/../mingw-w64-crt -I/var/lib/buildbot/slave-vista64-cyg32/cygwin-x86/build/mingw/obj/../mingw-w64-crt/include64 -D_CRTBLD -I/var/lib/buildbot/slave-vista64-cyg32/cygwin-x86/build/root/mingw/include
 -pipe  -Wall -std=gnu99 -g -O2 -MT gdtoa/lib64_libmingwex_a-gethex.o -MD -MP -MF gdtoa/.deps/lib64_libmingwex_a-gethex.Tpo -c -o gdtoa/lib64_libmingwex_a-gethex.o `test -f 'gdtoa/gethex.c' || echo '/var/lib/buildbot/slave-vista64-cyg32/cygwin-x86/build/mingw/obj/../mingw-w64-crt/'`gdtoa/gethex.c
/var/lib/buildbot/slave-vista64-cyg32/cygwin-x86/build/mingw/obj/../mingw-w64-crt/gdtoa/gethex.c:
In function '__gethex_D2A':
/var/lib/buildbot/slave-vista64-cyg32/cygwin-x86/build/mingw/obj/../mingw-w64-crt/gdtoa/gethex.c:45:
internal compiler error: tree check: accessed elt 4 of tree_vec with 3
elts in find_switch_asserts, at tree-vrp.c:4346
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://gcc.gnu.org/bugs.html> for instructions.
make[1]: *** [gdtoa/lib64_libmingwex_a-gethex.o] Error 1
make[1]: Leaving directory
`/var/lib/buildbot/slave-vista64-cyg32/cygwin-x86/build/mingw/obj'
make: *** [all] Error 2


Here's the file:

http://mingw-w64.svn.sourceforge.net/viewvc/mingw-w64/trunk/mingw-w64-crt/gdtoa/gethex.c?view=markup


At this stage, the newly built gcc is used to build the crt, so it's the stage 1 gcc that is dying.