AVX(2) instructions in manylinux i686 wheels

[tomkooij]

I'm experiencing Illegal instruction exceptions on manylinux i686 wheels on several (recent) CPUs:

• Intel(R) Xeon(R) CPU E5-2680 v3 @ 2.50GHz
• Intel(R) Celeron(R) CPU N2830 @ 2.16GHz
  Illegal instructions also reported in illegal instruction in Array.read_array PyTables/PyTables#626

Playing with objdump I'm seeing AVX instructions in libhdf5extension.so in py27 manylinux wheel for v3.4.2. From the travis log it seems pytables is build using -mavx2 which should not happen for an i686 build.

@matthew-brett: Can you help setting the correct compiler arch -m flags?
(This might be due to the fact we are now building internal blosc, instead of the separate blosc lib)

travis log: (note the -mavx2 flag)

building 'tables.hdf5extension' extension
gcc -pthread -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -std=gnu99 -fPIC -DNDEBUG=1 -DHAVE_LZO2_LIB=1 -DHAVE_BZ2_LIB=1 -DHAVE_LZ4=1 -DHAVE_SNAPPY=1 -DHAVE_ZLIB=1 -DHAVE_ZSTD=1 -Ihdf5-blosc/src -Ic-blosc/blosc -Ic-blosc/internal-complibs/zlib-1.2.8 -Ic-blosc/internal-complibs/lz4-1.7.5 -Ic-blosc/internal-complibs/snappy-1.1.1 -Ic-blosc/internal-complibs/zstd-1.1.3 -Ic-blosc/internal-complibs/zstd-1.1.3/common -Ic-blosc/internal-complibs/zstd-1.1.3 -I/opt/python/cp27-cp27mu/lib/python2.7/site-packages/numpy/core/include -I/opt/python/cp27-cp27mu/include/python2.7 -c tables/hdf5extension.c -o build/temp.linux-i686-2.7/tables/hdf5extension.o -std=gnu99 -Isrc -DH5_USE_18_API -DH5Acreate_vers=2 -DH5Aiterate_vers=2 -DH5Dcreate_vers=2 -DH5Dopen_vers=2 -DH5Eclear_vers=2 -DH5Eprint_vers=2 -DH5Epush_vers=2 -DH5Eset_auto_vers=2 -DH5Eget_auto_vers=2 -DH5Ewalk_vers=2 -DH5E_auto_t_vers=2 -DH5Gcreate_vers=2 -DH5Gopen_vers=2 -DH5Pget_filter_vers=2 -DH5Pget_filter_by_id_vers=2 -DH5Tarray_create_vers=2 -DH5Tget_array_dims_vers=2 -DH5Z_class_t_vers=2 -DSHUFFLE_SSE2_ENABLED -msse2 -DSHUFFLE_AVX2_ENABLED -mavx2

[tomkooij]

Never mind, this is in pytables setup.py, it detects SSE2 and AVX2 and sets CFLAGS when the internal blosc is used.
Which means that everything (including cython extensions) get's compiled with -mavx2 when the internal blosc is used.

Travis log: https://s3.amazonaws.com/archive.travis-ci.org/jobs/223825312/log.txt

SSE2 detected
AVX2 detected

This can probably be fixed by using the external blosc: PyTables/PyTables#627

[tomkooij]

Reverted back to using external blosc. (for now).

[tomkooij]

We can now use the internal C-Blosc by patching pytables/setup.py using the conda-forge patch: 45933ee