powerpc: Add support for future processor

This is the initial patch to support build infrastructure
for POWER10 architecture.

Extend and simplify the run-time detection for dynamic architecture support for z
to check HW_CAP and only use SIMD features if advertised by the OS.
While at it, also honor the env variable LD_HWCAP_MASK and do not use
the CPU features masked there.

Note that we can only use the SIMD features on z13 or newer (i.e.,
Vector Facility or Vector-Enhancements Facilities) when the operating
system supports properly context-switching the vector registers. The OS
advertises that support as a bit in the HW_CAP value in the auxiliary
vector. While all recent Linux kernels have that support, we should
maintain compatibility with older versions that may still be in use.

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

When building OpenBLAS with DYNAMIC_ARCH=1 on s390x (aka zarch), make
sure to include support for systems without the facilities introduced
with z13 (i.e., zarch_generic). Adjust runtime detection to fallback to
that generic code when running on a unknown platform other than Z13
through Z15.

When detecting a Z13 or newer system, add a check for gcc support for
the architecture-specific features before selecting the respective
kernel. Fallback to Z13 or generic code, in case.

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

* make building the bfloat16 BLAS functions conditional on BUILD_HALF

* pass the BUILD_HALF option to gensymbol

* Pass BUILD_HALF as a compiler define for dynamic_arch builds

This patch adds support for bfloat16 data type matrix multiplication kernel.
For architectures that don't support bfloat16, it is defined as unsigned short
(2 bytes).  Default unroll sizes can be changed as per architecture as done for
SGEMM and for now 8 and 4 are used for M and N.  Size of ncopy/tcopy can be
changed as per architecture requirement and for now, size 2 is used.

Added shgemm in kernel/power/KERNEL.POWER9 and tested in powerpc64le and
powerpc64.  For reference, added a small test compare_sgemm_shgemm.c to compare
sgemm and shgemm output.

This patch does not cover OpenBLAS test, benchmark and lapack tests for shgemm.
Complex type implementation can be discussed and added once this is approved.

Needed on systems with weak memory ordering - the inferior, partially working fix from #2544 was already removed in #2551

Issue: #2545

* Add another memory barrier in memory.c to prevent races in memory slot allocation

* Add an all-core test on Drone.io's ThunderX platform and modify dgemm_tester to use all 96 cores

* Add an ARMV7 iOS build on Travis

* thread_local appears to be unavailable on ARMV7 iOS

* Add no-thumb option for ARMV7 IOS build to get it to accept DMB ISH

* Make local labels in macros of nrm2_vfpv3.S compatible with the xcode assembler

Fix DYNAMIC_ARCH build for POWER9

Switch blas_server to use acq/rel semantics

Setting DYNAMIC_ARCH=1 on POWER9 does not build POWER9 files due to some
compiler version checks.  This patch fixes some of the macros that are used
to check compiler version.  On fixing those checks, there are some new make
failures related to icamin, icamax, isamin, isamax and caxpy files on POWER9.
This patch fixes those failures as well.

Heavy-weight locking isn't required to pass the work queue
pointer between threads and simple atomic acquire/release
semantics can be used instead. This is especially important as
pthread_mutex_lock() isn't fair.

We've observed substantial variation in runtime because of the
the unfairness of these locks which complety goes away with
this implementation.

The locks themselves are left to provide a portable way for
idling threads to sleep/wakeup after many unsuccessful iterations
waiting.

Fix barriers in level3_thread

The implementation is a hybird of the ARMV8 one with some of the
improved TX2 rountines along with specifying -march=v8.2-a

Patch out instances of Z15 in dynamic_zarch.c

There does not appear to be a Z15 kernel yet, causing link errors from the code. This patch fixes the issue.

Fix remaining bugs in parallel GEMM3M

as suggested by hjmndv in #2370

add in runtime cpu detection for zarch

It used to be 5ms, which might not be long enough in some cases for the
thread to exit well, but then when set to 5000 (5s), it would slow down
any program depending on OpenBlas.

Let's just set it to 50ms, which is at least 10 times longer than
originally, but still reasonable in case of failed thread termination.

* Update DYNAMIC_ARCH list of ARM64 targets for gmake
* Update arm64 cpu list for runtime detection
* Update DYNAMIC_ARCH list of ARM64 targets for cmake and add POWERPC targets

was originally in #2228 but that PR had misplaced the file in the toplevel directory

Fix race conditions in multithreaded GEMM3M

from #2322

by adding barriers (and a mutex lock for the non-OpenMP case) like it was already done for GEMM in level3_thread.c some time ago

This patch was submitted to the GIMP project by a publisher wishing to
keep confidentiality (hence anonymously). I just pass along the patch.
Here is the patch explanation which came with:

First they remind us what Microsoft documentation says about
TerminateThread:
> TerminateThread is a dangerous function that should only be used in
> the most extreme cases. You should call TerminateThread only if you
> know exactly what the target thread is doing, and you control all of
> the code that the target thread could possibly be running at the time
> of the termination.
(https://docs.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-terminatethread)

Then they say that 5 milliseconds time-out might not be long enough for
the thread to exit gracefully. They propose to set it to a much higher
value (for instance here 5 seconds).

And finally you should always check the return value of
WaitForSingleObject(). In particular you want to run TerminateThread()
only if WaitForSingleObject() failed, not on success case.

1. qalloc() appears to have been a special routine written for the PPC440-based QCDOC supercomputer(s) from around 2005, its source does not seem to be readily available. So switch the #if 1 in the code to rely on standard malloc() by default.
2. Utility functions like get_num_procs, get_num_threads that were added to the "normally" used memory.c in the meantime were still missing here.

* Add automatic fixups for OSX/IOS cross-compilation

* Add OSX/IOS cross-compilation test to Travis CI

* Handle platforms that lack hwcap.h by falling back to ARMV8

* Fix PROLOGUE for OSX/IOS

This is similar to fixes in gh-1929, but there was one remaining
occurance of this type of pattern in the driver/level2/*_thread.c
files.

* Add gcc7-generated assembly files for POWER8/9 isa/ica-min/max and POWER9 caxpy

To work around internal compiler errors encountered when compiling the original C source with gcc 4 and 5, and wrong code generated by gcc 8.3.0

* Use gcc-generated assembly instead of original C sources

to work around internal compiler errors encountered with gcc 4.8/5.4 and wrong code generation by gcc 8.3

* Use gcc-generated assembly instead of the original C source

to work around internal compiler errors encountered with gcc 4.8 and 5.4, and wrong code generation by gcc 8.3

* Add gcc7-generated assembler version of caxpy for power8

to work around wrong code generated by gcc 8.3

* Handle CONJ define for caxpyc

* Handle CONJ define for caxpyc

* Add gcc7-generated assembly cdot for POWER9

* Use prebuilt assembly for POWER9 cdot

created with gcc 7.3.1 to work around ICE in older gcc versions

* Exclude POWER9 from DYNAMIC_ARCH when gcc versions is lower than 6

* Update Makefile.system

* Use PROLOGUE macro to ensure correct function name for DYNAMIC_ARCH

* Disable POWER9 with old gcc versions