README.newarch

Notes on running HPCToolkit on KNL, power8/le and ARM.

Beginning with the 2016.12 release, HPCToolkit has preliminary support
for three new platforms: Knight's Landing (KNL), power8/le and ARM.
Old platforms: x86-64, powerpc, Blue Gene/Q and Cray XT/XK should
build and run as usual without any noticeable difference.

The two main issues for the new platforms are: ParseAPI and
InstructionAPI support from Dyninst for Control-Flow Graphs for
hpcstruct, and the unwinder.

KNL -- The key issue for KNL is for ParseAPI and InstructionAPI to
understand the new AVX instructions.  If ParseAPI does not understand
some instructions, then it will produce a poor control flow graph and
will miss large sections of some functions, resulting in poor results
in the viewer.  This is mostly an issue with the Intel compiler.

Power8/little-endian -- As of 2016.12, Dyninst does not support switch
tables for power8/le, resulting in poor control-flow graphs in some
cases.

ARM -- As of 2016.12, hpcrun does not have a native unwinder for ARM
and instead uses libunwind.  Applications that perform a high number
of calls to short functions from shared libraries may see a high
number (5-10%) of partial unwinds.  Libunwind does not do well on
interrupts taken inside the PLT, so for every call to a function
inside a shared library, there is a small window of vulnerability
where the unwind will fail.