Adding Hwloc library option for affinity mechanism
These changes allow libhwloc to be used as the topology discovery/affinity
mechanism for libomp. It is supported on Unices. The code additions:
- Canonicalize KMP_CPU_* interface macros so bitmask operations are implementation independent and work with both hwloc bitmaps and libomp bitmaps. So there are new KMP_CPU_ALLOC_* and KMP_CPU_ITERATE() macros and the like. These are all in kmp.h and appropriately placed.
- Hwloc topology discovery code in kmp_affinity.cpp. This uses the hwloc interface to create a libomp address2os object which the rest of libomp knows how to handle already.
- To build, use -DLIBOMP_USE_HWLOC=on and -DLIBOMP_HWLOC_INSTALL_DIR=/path/to/install/dir [default /usr/local]. If CMake can't find the library or hwloc.h, then it will tell you and exit.
Differential Revision: http://reviews.llvm.org/D13991