This patch adds Hardware Transaction Memory (HTM) support supported by
ISA 2.07 (POWER8). The intrinsic support is based on GCC one , with
both 'PowerPC HTM Low Level Built-in Functions' and 'PowerPC HTM High
Level Inline Functions' implemented.
Along with builtins a new driver switch is added to enable/disable HTM
instruction support (-mhtm) and a header with common definitions (mostly
to parse the TFHAR register value). The HTM switch also sets a
preprocessor builtin HTM.
The HTM usage requires a recently newer kernel with PPC HTM enabled.
Tested on powerpc64 and powerpc64le.
This is send along a llvm patch to enabled the builtins and option