[Bug target/44606] Wrong SPE floating point during computation

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

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44606

--- Comment #10 from David KÃhling <dvdkhlng at gmx dot de> 2010-11-02 14:39:12 UTC ---
I can reproduce this bug with gcc-4_4-branch SVN HEAD, compiling gcc in
cross-compile mode and running the resulting executable with qemu-ppc. 
Instructions to reproduce everything without any PPC hardware involved (tested
on Ubuntu Maverick/AMD64):

Get a powerpcspe sysroot:

 apt-cross -a powerpcspe -S sid -m http://ftp.de.debian.org/debian-ports \
        libdb1-compat libdb4.8 libc6 libc6-dev linux-libc-dev \
    zlib1g zlib1g-dev libmpfr-dev
 apt-cross -a powerpcspe -S unreleased -m http://ftp.de.debian.org/debian-ports
\
        libdb1-compat libdb4.8 libc6 libc6-dev linux-libc-dev \
    zlib1g zlib1g-dev libmpfr-dev

(repeat a few times until all dependencies resolved)

get Debian SID binutils source, then compile&install in cross-compile mode:

 dpkg-source -x binutils_*.dsc
 cd binutils-* && \
        TARGET=powerpcspe fakeroot debian/rules binary-cross
 dpkg -i binutils-powepc-linux-gnuspe-*.deb

Get GCC from SVN and compile minimal C-only version:

 svn co svn://gcc.gnu.org/svn/gcc/branches/gcc-4_4-branch
 mkdir -p build
    cd build && ../gcc-4_4-branch/configure \
        --target=powerpc-linux-gnuspe \
        -with-cpu=8548 --enable-e500_double --with-long-double-128 \
        --enable-languages=c --disable-multilib \
        --prefix=/usr --with-headers=/usr/powerpc-linux-gnuspe/include \
        --with-libs=/usr/powerpc-linux-gnuspe/lib 
    make -C build -j5

Compile test-cases available as attachments to this bug, i.e. test.c:

 build/gcc/xgcc \
    -B./build/gcc/ -B/usr/powerpc-linux-gnuspe/bin/ \
    -B/usr/powerpc-linux-gnuspe/lib/ \
    -isystem /usr/powerpc-linux-gnuspe/include \
    -isystem /usr/powerpc-linux-gnuspe/sys-include \
    -fverbose-asm -dA -O2 -o test test.c

Use Ubuntu's qemu user-space emulation to run resulting executable:

 rootfs=/usr/powerpc-linux-gnuspe
 /usr/bin/qemu-ppc -cpu 'MPC8548E_v21' \
        -E LD_LIBRARY_PATH=$rootfs/lib/ $rootfs/lib/ld.so.1 \
        ./test

Repeat the same with -O0 and note the difference.  This test fails for all the
3 .c files attached here.  Output for tc-resize.c matches the output documented
by Sebastian, so I'd say qemu is doing it right.