[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

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

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

README.rst

**LIBOMP_USE_ADAPTIVE_LOCKS** = ``ON|OFF``
   Include adaptive locks, based on Intel(R) Transactional Synchronization
   Extensions (Intel(R) TSX).  This feature is x86 specific and turned ``ON``
   by default for IA-32 architecture and Intel(R) 64 architecture.
 
 **LIBOMP_USE_INTERNODE_ALIGNMENT** = ``OFF|ON``
   Align certain data structures on 4096-byte.  This option is useful on
   multi-node systems where a small ``CACHE_LINE`` setting leads to false sharing.
 
-**LIBOMP_OMPT_SUPPORT** = ``OFF|ON``
-  Include support for the OpenMP Tools Interface (OMPT).
+**LIBOMP_OMPT_SUPPORT** = ``ON|OFF``
+  Include support for the OpenMP Tools Interface (OMPT). 
+  This option is supported and ``ON`` by default for x86, x86_64, AArch64, and 
+  PPC64 on Linux, Windows, and mac OS.
+  This option is ``OFF`` if this feature is not supported for the platform.
 
 **LIBOMP_OMPT_OPTIONAL** = ``ON|OFF``
   Include support for optional OMPT functionality.  This option is ignored if
   **LIBOMP_OMPT_SUPPORT** is ``OFF``.
 
 **LIBOMP_STATS** = ``OFF|ON``
   Include stats-gathering code.
 

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
+# OMPT-support defaults to ON for OpenMP 5.0+ and if the requirements in
+# cmake/config-ix.cmake are fulfilled.
+set(OMPT_DEFAULT FALSE)
+if ((${LIBOMP_OMP_VERSION} GREATER 49) AND (LIBOMP_HAVE_OMPT_SUPPORT))
+  set(OMPT_DEFAULT TRUE)
+endif()
+set(LIBOMP_OMPT_SUPPORT ${OMPT_DEFAULT} CACHE BOOL
+  "OMPT-support?")
+
 set(LIBOMP_OMPT_DEBUG FALSE CACHE BOOL
   "Trace OMPT initialization?")
-#after testing: turn on ompt support by default for OpenMP 5.0 and higher
-set(LIBOMP_OMPT_SUPPORT FALSE CACHE BOOL
-  "OMPT-support?")
 set(LIBOMP_OMPT_OPTIONAL TRUE CACHE BOOL
   "OMPT-optional?")
 if(LIBOMP_OMPT_SUPPORT AND (NOT LIBOMP_HAVE_OMPT_SUPPORT))
   libomp_error_say("OpenMP Tools Interface requested but not available in this implementation")
 endif()
 if(LIBOMP_OMPT_SUPPORT AND (${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()

runtime/cmake/config-ix.cmake

 check_include_files("windows.h;psapi.h" LIBOMP_HAVE_PSAPI_H)
 check_library_exists(psapi EnumProcessModules "" LIBOMP_HAVE_LIBPSAPI)
 if(LIBOMP_HAVE_PSAPI_H AND LIBOMP_HAVE_LIBPSAPI)
   set(LIBOMP_HAVE_PSAPI TRUE)
 endif()
 if(NOT LIBOMP_HAVE___BUILTIN_FRAME_ADDRESS)
   set(LIBOMP_HAVE_OMPT_SUPPORT FALSE)
 else()
-  if((WIN32 AND LIBOMP_HAVE_PSAPI) OR APPLE OR (NOT WIN32 AND LIBOMP_HAVE_WEAK_ATTRIBUTE))
+  if( # hardware architecture supported?
+     ((LIBOMP_ARCH STREQUAL x86_64) OR
+      (LIBOMP_ARCH STREQUAL i386) OR
+#      (LIBOMP_ARCH STREQUAL arm) OR
+      (LIBOMP_ARCH STREQUAL aarch64) OR
+      (LIBOMP_ARCH STREQUAL ppc64le) OR
+      (LIBOMP_ARCH STREQUAL ppc64))
+     AND # OS supported?
+     ((WIN32 AND LIBOMP_HAVE_PSAPI) OR APPLE OR (NOT WIN32 AND LIBOMP_HAVE_WEAK_ATTRIBUTE)))
     set(LIBOMP_HAVE_OMPT_SUPPORT TRUE)
   else()
     set(LIBOMP_HAVE_OMPT_SUPPORT FALSE)
   endif()
 endif()
 
 # Check if HWLOC support is available
 if(${LIBOMP_USE_HWLOC})