[OpenMP] Disabled profiling in `libomp` by default to unblock link errors
Link error occurred when time profiling in libomp is enabled by default
because `libomp` is assumed to be a C library but the dependence on
`libLLVMSupport` for profiling is a C++ library. Currently the issue blocks all
OpenMP tests in Phabricator.
This patch set a new CMake option `OPENMP_ENABLE_LIBOMP_PROFILING` to
enable/disable the feature. By default it is disabled. Note that once time
profiling is enabled for `libomp`, it becomes a C++ library.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D95585
GitOrigin-RevId: c571b168349fdf22d1dc8b920bcffa3d5161f0a2
diff --git a/CMakeLists.txt b/CMakeLists.txt
index f89857d..b8a2822 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -81,6 +81,7 @@
${ENABLE_LIBOMPTARGET})
option(OPENMP_ENABLE_LIBOMPTARGET_PROFILING "Enable time profiling for libomptarget."
${ENABLE_LIBOMPTARGET})
+option(OPENMP_ENABLE_LIBOMP_PROFILING "Enable time profiling for libomp." OFF)
# Build host runtime library, after LIBOMPTARGET variables are set since they are needed
# to enable time profiling support in the OpenMP runtime.
diff --git a/docs/design/Runtimes.rst b/docs/design/Runtimes.rst
index 016b88b..ad36e43 100644
--- a/docs/design/Runtimes.rst
+++ b/docs/design/Runtimes.rst
@@ -48,7 +48,10 @@
`Speedscope App`_. Building this feature depends on the `LLVM Support Library`_
for time trace output. Using this library is enabled by default when building
using the CMake option ``OPENMP_ENABLE_LIBOMPTARGET_PROFILING``. The output will
-be saved to the filename specified by the environment variable.
+be saved to the filename specified by the environment variable. For multi-threaded
+applications, profiling in ``libomp`` is also needed. Setting the CMake option
+``OPENMP_ENABLE_LIBOMP_PROFILING=ON`` to enable the feature. Note that this will
+turn ``libomp`` into a C++ library.
.. _`Chrome Tracing`: https://www.chromium.org/developers/how-tos/trace-event-profiling-tool
diff --git a/runtime/CMakeLists.txt b/runtime/CMakeLists.txt
index 9fdd04f..8828ff8 100644
--- a/runtime/CMakeLists.txt
+++ b/runtime/CMakeLists.txt
@@ -34,7 +34,6 @@
# Should assertions be enabled? They are on by default.
set(LIBOMP_ENABLE_ASSERTIONS TRUE CACHE BOOL
"enable assertions?")
- set(LIBOMPTARGET_PROFILING_SUPPORT FALSE)
else() # Part of LLVM build
# Determine the native architecture from LLVM.
string(TOLOWER "${LLVM_TARGET_ARCH}" LIBOMP_NATIVE_ARCH)
@@ -66,10 +65,11 @@
libomp_get_architecture(LIBOMP_ARCH)
endif ()
set(LIBOMP_ENABLE_ASSERTIONS ${LLVM_ENABLE_ASSERTIONS})
- # Time profiling support
- set(LIBOMPTARGET_PROFILING_SUPPORT ${OPENMP_ENABLE_LIBOMPTARGET_PROFILING})
endif()
+# Time profiling support
+set(LIBOMP_PROFILING_SUPPORT ${OPENMP_ENABLE_LIBOMP_PROFILING})
+
# FUJITSU A64FX is a special processor because its cache line size is 256.
# We need to pass this information into kmp_config.h.
if(LIBOMP_ARCH STREQUAL "aarch64")
diff --git a/runtime/src/CMakeLists.txt b/runtime/src/CMakeLists.txt
index 9c5dba5..822f9ca 100644
--- a/runtime/src/CMakeLists.txt
+++ b/runtime/src/CMakeLists.txt
@@ -50,9 +50,8 @@
include_directories(${LIBOMP_HWLOC_INSTALL_DIR}/include)
endif()
-# Building with time profiling support for libomptarget requires
-# LLVM directory includes.
-if(LIBOMPTARGET_PROFILING_SUPPORT)
+# Building with time profiling support requires LLVM directory includes.
+if(LIBOMP_PROFILING_SUPPORT)
include_directories(
${LLVM_MAIN_INCLUDE_DIR}
${LLVM_INCLUDE_DIR}
@@ -144,7 +143,7 @@
libomp_get_libflags(LIBOMP_CONFIGURED_LIBFLAGS)
# Build libomp library. Add LLVMSupport dependency if building in-tree with libomptarget profiling enabled.
-if(OPENMP_STANDALONE_BUILD OR (NOT OPENMP_ENABLE_LIBOMPTARGET_PROFILING))
+if(OPENMP_STANDALONE_BUILD OR (NOT OPENMP_ENABLE_LIBOMP_PROFILING))
add_library(omp ${LIBOMP_LIBRARY_KIND} ${LIBOMP_SOURCE_FILES})
# Linking command will include libraries in LIBOMP_CONFIGURED_LIBFLAGS
target_link_libraries(omp ${LIBOMP_CONFIGURED_LIBFLAGS} ${CMAKE_DL_LIBS})
@@ -153,6 +152,8 @@
LINK_LIBS ${LIBOMP_CONFIGURED_LIBFLAGS} ${CMAKE_DL_LIBS}
LINK_COMPONENTS Support
)
+ # libomp must be a C++ library such that it can link libLLVMSupport
+ set(LIBOMP_LINKER_LANGUAGE CXX)
endif()
set_target_properties(omp PROPERTIES
diff --git a/runtime/src/kmp_config.h.cmake b/runtime/src/kmp_config.h.cmake
index 3d682c6..f6aee71 100644
--- a/runtime/src/kmp_config.h.cmake
+++ b/runtime/src/kmp_config.h.cmake
@@ -44,8 +44,8 @@
#define OMPT_DEBUG LIBOMP_OMPT_DEBUG
#cmakedefine01 LIBOMP_OMPT_SUPPORT
#define OMPT_SUPPORT LIBOMP_OMPT_SUPPORT
-#cmakedefine01 LIBOMPTARGET_PROFILING_SUPPORT
-#define OMPTARGET_PROFILING_SUPPORT LIBOMPTARGET_PROFILING_SUPPORT
+#cmakedefine01 LIBOMP_PROFILING_SUPPORT
+#define OMP_PROFILING_SUPPORT LIBOMP_PROFILING_SUPPORT
#cmakedefine01 LIBOMP_OMPT_OPTIONAL
#define OMPT_OPTIONAL LIBOMP_OMPT_OPTIONAL
#cmakedefine01 LIBOMP_USE_ADAPTIVE_LOCKS
diff --git a/runtime/src/kmp_runtime.cpp b/runtime/src/kmp_runtime.cpp
index 4a0634d..a6e32bd 100644
--- a/runtime/src/kmp_runtime.cpp
+++ b/runtime/src/kmp_runtime.cpp
@@ -32,7 +32,7 @@
#include "ompt-specific.h"
#endif
-#if OMPTARGET_PROFILING_SUPPORT
+#if OMP_PROFILING_SUPPORT
#include "llvm/Support/TimeProfiler.h"
static char *ProfileTraceFile = nullptr;
#endif
@@ -5740,7 +5740,7 @@
/* ------------------------------------------------------------------------ */
void *__kmp_launch_thread(kmp_info_t *this_thr) {
-#if OMPTARGET_PROFILING_SUPPORT
+#if OMP_PROFILING_SUPPORT
ProfileTraceFile = getenv("LIBOMPTARGET_PROFILE");
// TODO: add a configuration option for time granularity
if (ProfileTraceFile)
@@ -5848,7 +5848,7 @@
KA_TRACE(10, ("__kmp_launch_thread: T#%d done\n", gtid));
KMP_MB();
-#if OMPTARGET_PROFILING_SUPPORT
+#if OMP_PROFILING_SUPPORT
llvm::timeTraceProfilerFinishThread();
#endif
return this_thr;
