[OMPT] Build runtime with OMPT support by default

[protze.joachim]

Summary

As discussed on openmp-dev mailing list.

This patch enables OMPT by default if version 50 or later is built and the config says, that OMPT will be supported.

[Hahnfeld]

I don't think we should enable this unconditionally, only for the architectures where we tested and are sure that the tests will pass: x86, x86_64, ppc64, aarch64 on Linux, macOS if we want to. With the current change we will get into trouble at least on MIPS(64).

runtime/CMakeLists.txt

305–309

I think it would be better to only have one definition of cache variables:

set(OMPT_DEFAULT FALSE)
if (...)
  set(OMPT_DEFAULT TRUE)
endif()
set(LIBOMP_OMPT_SUPPORT TRUE CACHE BOOL
    "Enable support for OMPT?")

[protze.joachim]

I added the requirement for hardware architecture support to LIBOMP_HAVE_OMPT_SUPPORT.
This way one would also get an error when manually turing LIBOMP_OMPT_SUPPORT=on on an unsupported architecture.

Also implemented Jonas' suggestion.

[pawosm01]

+1

[Hahnfeld]

runtime/cmake/config-ix.cmake

242 ↗

(On Diff #128073)

I think we haven't adjusted the tests for ARM 32 bit yet? @pawosm01

[pawosm01]

@Hahnfeld gosh, you're right and I don't work with 32-bit systems nowadays so I need to track down one of those still kept online. Being far from the office isn't helping, so it won't happen immediately.

[protze.joachim]

Removed 32 bit ARM from the list of supported architectures until it is tested.

[Hahnfeld]

Looks good so far. Can you document the change of the default value in the (just committed) README.rst?

[protze.joachim]

Updated the README

[Hahnfeld]

LG. I'd feel better with an explicit acknowledgment from Intel though...

(We should probably add a few sentences to Clang's release notes so that users know the reason should they see a performance degradation. I can handle that after this patch landed.)

README.rst

195–196 ↗

(On Diff #128403)

Should we mention which platforms are supported? Like This option is ON by default for x86, x86_64, AArch64, and PPC64 on Linux, Windows, and mac OS?

[protze.joachim]

Updated the README

runtime/CMakeLists.txt

if(LIBOMP_USE_ITT_NOTIFY AND NOT LIBOMP_ENABLE_SHARED)
   set(LIBOMP_USE_ITT_NOTIFY FALSE)
 endif()
 
 if(LIBOMP_USE_VERSION_SYMBOLS AND (NOT LIBOMP_ENABLE_SHARED) )
   message(STATUS "Version symbols not supported for static libraries - forcing Version symbols functionality off")
   set (LIBOMP_USE_VERSION_SYMBOLS FALSE)
 endif()
 
-# OMPT-support
-set(LIBOMP_OMPT_DEBUG FALSE CACHE BOOL
-  "Trace OMPT initialization?")
-#after testing: turn on ompt support by default for OpenMP 5.0 and higher
+# OMPT-support defaults to ON for OpenMP 5.0+ and if the requirements in
+# cmake/config-ix.cmake are fulfilled.
+if((${LIBOMP_OMP_VERSION} GREATER 49) AND (LIBOMP_HAVE_OMPT_SUPPORT))
+  set(LIBOMP_OMPT_SUPPORT TRUE CACHE BOOL
+    "OMPT-support?")
+else()
   set(LIBOMP_OMPT_SUPPORT FALSE CACHE BOOL
     "OMPT-support?")
+endif()
+
+set(LIBOMP_OMPT_DEBUG FALSE CACHE BOOL
+  "Trace OMPT initialization?")
 set(LIBOMP_OMPT_OPTIONAL TRUE CACHE BOOL
   "OMPT-optional?")
 if(LIBOMP_OMPT_SUPPORT AND (NOT LIBOMP_HAVE_OMPT_SUPPORT))
   libomp_error_say("OpenMP Tools Interface requested but not available in this implementation")
 endif()
 if(LIBOMP_OMPT_SUPPORT AND (${LIBOMP_OMP_VERSION} LESS 50))
   libomp_error_say("OpenMP Tools Interface only available with OpenMP 5.0, LIBOMP_OMP_VERSION is ${LIBOMP_OMP_VERSION}")
 endif()