pocl 1.1

Highlights

• LLVM 6.0 is now supported.

• Reintroduced experimental SPIR LLVM bitcode support to pocl.
  Requires LLVM 5 or newer. New experimental feature: SPIR-V support;
  requires a working llvm-spirv converter. Currently only loading
  of SPIR-V binaries by pocl is supported, not output.
  See docs/features.rst for more details.

• Refactored pocl cache now does away with LLVM file locks and relies
  entirely on system calls for proper synchronization. Additionally,
  cache file writes are now fdatasync()ed.

• Improved kernel compilation time (with cold cache). Improvement
  depends on sources - it's bigger for large programs with many kernels.
  Luxmark now compiles in seconds instead of dozens of seconds;
  internal pocl tests run in 30-50% less time.

• LLVM Scalarizer pass is now only called for SPMD devices. Performance
  change varies across tests, but positive seems to outweigh negative.

• Implemented uninitialization callback for device drivers. This is
  triggered when the last cl_context is released. Currently only the
  CPU driver implements the callback.

• Removed libpoclu from installed files; this library contains helpers
  for pocl's internal tests, and from installed files was only used by
  poclcc, which has been updated to not rely on it.

• POCL_MAX_WORK_GROUP_SIZE is now respected by all devices. This variable
  limits the reported maximum WG sizes & dimensions; tuning max WG size
  may improve performance due to cache locality improvement.

• CL_PLATFORM_VERSION now contains much more information about how
  pocl was built.

• For users still building with Vecmathlib, performance should be back
  to levels of pocl 0.14 (there was a huge drop caused by a change
  in -O0 optimization level of LLVM 5.0).

• Improved support for ARM and ARM64 architectures. All internal tests
  now pass (on Cortex-A53 and Cortex-A15), although it's still far
  from full conformance.