error: 'asm' operand has impossible constraints when compiling gromacs 5.1 on PPC64 and PPC64LE with VSX SMD

[Dominik 'Rathann' Mierzejewski]

Hello!
When gromacs-5.1 is configured for double precision, I get the following
compilation error when building the internal tests (make check):
[...]
[ 94%] Building CXX object src/gromacs/simd/tests/CMakeFiles/simd-test.dir/simd_integer.cpp.o
cd /builddir/build/BUILD/gromacs-5.1/openmpi_d/src/gromacs/simd/tests && /usr/bin/c++   -DGMX_DOUBLE -DGTEST_USE_OWN_TR1_TUPLE=1 -DHAVE_CONFIG_H -DTEST_DATA_PATH=\"src/gromacs/simd/tests\" -DTEST_TEMP_PATH=\"/builddir/build/BUILD/gromacs-5.1/openmpi_d/src/gromacs/simd/tests/Testing/Temporary\" -mvsx   -std=c++0x -O2 -g -pipe -Wall -Werror=format-security -Wp
,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -m64  -Wundef -Wextra -Wno-missing-field-initializers -Wpointer-arith -Wall -Wno-unused-function   -funroll-all-loops -fexcess-precision=fast  -Wno-array-bounds  -isystem /builddir/build/BUILD/gromacs-5.1/src/external/gmock-1.7.0/gtest/include -isystem /builddir/build/BUILD/gromacs-5.1/src/external/gmock-1.7.0/include -I/builddir/build/BUILD/gromacs-5.1/openmpi_d/src/external/tng_io/include -I/builddir/build/BUILD/gromacs-5.1/src/external/tng_io/include -I/builddir/build/BUILD/gromacs-5.1/openmpi_d/src -I/builddir/build/BUILD/gromacs-5.1/src/external/thread_mpi/include -I/builddir/build/BUILD/gromacs-5.1/src -I/usr/include/openmpi-ppc64    -Wno-unused-variable -o CMakeFiles/simd-test.dir/simd_integer.cpp.o -c /builddir/build/BUILD/gromacs-5.1/src/gromacs/simd/tests/simd_integer.cpp
In file included from /builddir/build/BUILD/gromacs-5.1/src/gromacs/simd/simd.h:138:0,
                 from /builddir/build/BUILD/gromacs-5.1/src/gromacs/simd/tests/simd_integer.cpp:37:
/builddir/build/BUILD/gromacs-5.1/src/gromacs/simd/impl_ibm_vsx/impl_ibm_vsx.h: In member function 'virtual void gmx::test::{anonymous}::SimdIntegerTest_gmxSimdCvtI2R_Test::TestBody()':
/builddir/build/BUILD/gromacs-5.1/src/gromacs/simd/impl_ibm_vsx/impl_ibm_vsx.h:452:80: error: 'asm' operand has impossible constraints
     __asm__ ("xvcvsxwdp %0,%1" : "=ww" (x) : "ww" ((__vector signed int) (ix)));
                                                                                ^
/builddir/build/BUILD/gromacs-5.1/src/gromacs/simd/impl_ibm_vsx/impl_ibm_vsx.h:452:80: error: 'asm' operand has impossible constraints
     __asm__ ("xvcvsxwdp %0,%1" : "=ww" (x) : "ww" ((__vector signed int) (ix)));
                                                                                ^
src/gromacs/simd/tests/CMakeFiles/simd-test.dir/build.make:209: recipe for target 'src/gromacs/simd/tests/CMakeFiles/simd-test.dir/simd_integer.cpp.o' failed
make[3]: *** [src/gromacs/simd/tests/CMakeFiles/simd-test.dir/simd_integer.cpp.o] Error 1
[...]

This happens on:

$ cat /proc/cpuinfo 
processor	: 0
cpu		: POWER8E (raw), altivec supported
clock		: 3425.000000MHz
revision	: 2.1 (pvr 004b 0201)

processor	: 1
cpu		: POWER8E (raw), altivec supported
clock		: 3425.000000MHz
revision	: 2.1 (pvr 004b 0201)

timebase	: 512000000
platform	: pSeries
model		: IBM pSeries (emulated by qemu)
machine		: CHRP IBM pSeries (emulated by qemu)

in Fedora rawhide (F24) chroot while building the gromacs package
(http://pkgs.fedoraproject.org/cgit/gromacs.git) under mock.
You have to remove the %ifnarch ppc64 ppc64le part in %install section
to reproduce.

More details here: http://redmine.gromacs.org/issues/1808

AltiVec assembly is far beyond my skill, so I'd appreciate it if someone
could help figure it out.

Regards,
Dominik
-- 
Fedora http://fedoraproject.org/wiki/User:Rathann
RPMFusion http://rpmfusion.org
"Faith manages."
        -- Delenn to Lennier in Babylon 5:"Confessions and Lamentations"