Avoid out of bounds access on invalid memory free

Lazyly reinit threads after a fork in OMP mode

fix clang std=c18 compilation on aarch64

This initializes the per-thread memory buffers which get
cleared/released on a fork via pthread_at_fork. Not doing so leads to
each thread calling blas_memory_alloc on almost every execution which
slows down the code significantly as the threads race for the memory
allocation using locks to serialize that.

Check for __linux rather than linux in cpuid code and benchmarks

Consolidate usage of backticks for build options

and add a fallback for unsupported operating systems in detect()

rebase

Optimize dcopy/zcopy for POWER10

This patch makes use of new POWER10 vector pair instructions for
loads and stores. Tested in simulator and no new failures.

There were some build options in the README that were not
highlighted. Now all are highlighted.

Optimize the performance of daxpy by using universal intrinsics

FIx underflow/rounding errors in LAPACK (S,D)LANV2

Reference-LAPACK PR 445, fixing their issue 263

Readmefixes

rebase

fix a bug of trmm

Add an AWS-Graviton2 build to Travis CI

rebase

Add an OSX build with xcode12

s390x: fix cscal and zscal implementations

The implementation of complex scalar * vector multiplication for Z14
makes some LAPACK tests fail because the numerical differences to the
reference implementation exceed the threshold (as can be seen by running
make lapack-test and replacing kernel/zarch/cscal.c with a generic
implementation for comparison).

The complex multiplication uses terms of the form a * b + c * d for both
real and imaginary parts. The assembly code (and compiler-emitted code
as well) uses fused multiply add operations for the second product and
sum. The results can be "surprising", for example when both terms in the
imaginary part nearly cancel each other out. In that case, the second
product contributes more digits to the sum than the first product that
has been rounded before.

One option is to use separate multiplications (which then round the same
way) and a distinct add. Change the code to pursue that path, by (1)
requesting the compiler not to contract the operations into FMAs and (2)
replacing the assembly kernel with corresponding vectorized C code
(where change 1 also applies).

Signed-off-by: Marius Hillenbrand <mhillen@linux.ibm.com>

Make clang slightly more cautious when contracting floating-point
operations (e.g., when applying fused multiply add) by setting
-ffp-contract=on (instead of fast).

Signed-off-by: Marius Hillenbrand <mhillen@linux.ibm.com>

... to facilitate reuse beyond gemm_vec.c and avoid code duplication.

Signed-off-by: Marius Hillenbrand <mhillen@linux.ibm.com>

Fix workspace query in LAPACK xGELQ (Reference-LAPACK 443)

rebase

Optimize daxpy/zaxpy for POWER10

This patch makes use of new POWER10 vector pair instructions for
loads and stores. Tested in simulator and no new failures.

Make thread safety tests available to CMAKE and support running only the GEMV version

s390x/DYNAMIC_ARCH: fixup broken merge and reapply simplification

An unrelated commit and merge inadvertently reverted our recent two
changes for simplifying DYNAMIC_ARCH on s390x. Simply reapply the
changes.

Simplify detection of which kernels we can compile on s390x. Instead of
decoding the gcc version in a complicated manner, just check if CC
supports a given -march=archXY flag. Together with the next patch, we
thereby gain support for builds with LLVM/clang with DYNAMIC_ARCH=1.

To enable builds with DYNAMIC_ARCH with older compiler releases, the
Makefile and drivers/other/dynamic_arch.c need a common view of the
architecture support built into the library.

We follow the notation from x86 when used with DYNAMIC_LIST, where
defines DYN_<ARCH NAME> denote support for a given generation to be
built in. Since there are far fewer architecture generations in OpenBLAS
for s390x, that does not bloat command lines too much.

Closes: #2842
Fixes: ba644378dc ("Copy BUILD_ options available to the compiler flags"

Signed-off-by: Marius Hillenbrand <mhillen@linux.ibm.com>