[cmake] Add an option to build llvm with IR PGO

[vsk]

Summary

This adds an LLVM_ENABLE_IR_PGO option to enable building llvm and its tools with IR PGO instrumentation.

Usage: -DLLVM_BUILD_INSTRUMENTED=On -DLLVM_ENABLE_IR_PGO=On (both options must be enabled)

[davidxl]

cmake/modules/HandleLLVMOptions.cmake

751 ↗

(On Diff #115938)

-fprofile-generate=<> is supported as well, why not using that?

[vsk]

cmake/modules/HandleLLVMOptions.cmake

751 ↗

(On Diff #115938)

That flag treats its argument as a directory and appends '/default_%m.profraw'. It's not possible to use it along with LLVM_PROFILE_FILE_PATTERN off-the-shelf, as that would introduce multiple %Nm specifiers.

Would you prefer finding the dirname of LLVM_PROFILE_FILE_PATTERN, and using that instead?

[davidxl]

cmake/modules/HandleLLVMOptions.cmake

751 ↗

(On Diff #115938)

"Would you prefer finding the dirname of LLVM_PROFILE_FILE_PATTERN, and using that instead?" -- that seems better -- to avoid exposing -fprofile-instrument-path

[vsk]

• Use -fprofile-generate=<data-dir> instead of a hidden frontend option. I tested this by building llvm-config with LLVM_BUILD_INSTRUMENTED and LLVM_ENABLE_IR_PGO -- both workflows lgtm.

[vsk]

• Make it possible to use LLVM_ENABLE_IR_PGO and LLVM_BUILD_INSTRUMENTED together. This will make it possible to use the Apple PGO cmake cache with IR PGO.

[davidxl]

lgtm

llvm/trunk/CMakeLists.txt

 endif()
 
 if (MSVC_IDE AND NOT (MSVC_VERSION LESS 1900))
   option(LLVM_ADD_NATIVE_VISUALIZERS_TO_SOLUTION "Configure project to use Visual Studio native visualizers" TRUE)
 else()
   set(LLVM_ADD_NATIVE_VISUALIZERS_TO_SOLUTION FALSE CACHE INTERNAL "For Visual Studio 2013, manually copy natvis files to Documents\\Visual Studio 2013\\Visualizers" FORCE)
 endif()
 
-if (LLVM_BUILD_INSTRUMENTED OR LLVM_BUILD_INSTRUMENTED_COVERAGE)
+if (LLVM_BUILD_INSTRUMENTED OR LLVM_BUILD_INSTRUMENTED_COVERAGE OR
+    LLVM_ENABLE_IR_PGO)
   if(NOT LLVM_PROFILE_MERGE_POOL_SIZE)
     # A pool size of 1-2 is probably sufficient on a SSD. 3-4 should be fine
     # for spining disks. Anything higher may only help on slower mediums.
     set(LLVM_PROFILE_MERGE_POOL_SIZE "4")
   endif()
   if(NOT LLVM_PROFILE_FILE_PATTERN)
     if(NOT LLVM_PROFILE_DATA_DIR)
-      file(TO_NATIVE_PATH "${LLVM_BINARY_DIR}/profiles/%${LLVM_PROFILE_MERGE_POOL_SIZE}m.profraw" LLVM_PROFILE_FILE_PATTERN)
-    else()
-      file(TO_NATIVE_PATH "${LLVM_PROFILE_DATA_DIR}/%${LLVM_PROFILE_MERGE_POOL_SIZE}m.profraw" LLVM_PROFILE_FILE_PATTERN)
+      file(TO_NATIVE_PATH "${LLVM_BINARY_DIR}/profiles" LLVM_PROFILE_DATA_DIR)
     endif()
+    file(TO_NATIVE_PATH "${LLVM_PROFILE_DATA_DIR}/%${LLVM_PROFILE_MERGE_POOL_SIZE}m.profraw" LLVM_PROFILE_FILE_PATTERN)
   endif()
 endif()
 
 if (LLVM_BUILD_STATIC)
   set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -static")
 endif()
 
 # Override the default target with an environment variable named by LLVM_TARGET_TRIPLE_ENV.

llvm/trunk/cmake/modules/HandleLLVMOptions.cmake

 
 # Provide public options to globally control RTTI and EH
 option(LLVM_ENABLE_EH "Enable Exception handling" OFF)
 option(LLVM_ENABLE_RTTI "Enable run time type information" OFF)
 if(LLVM_ENABLE_EH AND NOT LLVM_ENABLE_RTTI)
   message(FATAL_ERROR "Exception handling requires RTTI. You must set LLVM_ENABLE_RTTI to ON")
 endif()
 
+option(LLVM_ENABLE_IR_PGO "Build LLVM and tools with IR PGO instrumentation (experimental)" Off)
+mark_as_advanced(LLVM_ENABLE_IR_PGO)
+
 option(LLVM_BUILD_INSTRUMENTED "Build LLVM and tools with PGO instrumentation" Off)
 mark_as_advanced(LLVM_BUILD_INSTRUMENTED)
-append_if(LLVM_BUILD_INSTRUMENTED "-fprofile-instr-generate='${LLVM_PROFILE_FILE_PATTERN}'"
+
+if (LLVM_BUILD_INSTRUMENTED)
+  if (LLVM_ENABLE_IR_PGO)
+    append("-fprofile-generate='${LLVM_PROFILE_DATA_DIR}'"
       CMAKE_CXX_FLAGS
       CMAKE_C_FLAGS
       CMAKE_EXE_LINKER_FLAGS
       CMAKE_SHARED_LINKER_FLAGS)
+  else()
+    append("-fprofile-instr-generate='${LLVM_PROFILE_FILE_PATTERN}'"
+      CMAKE_CXX_FLAGS
+      CMAKE_C_FLAGS
+      CMAKE_EXE_LINKER_FLAGS
+      CMAKE_SHARED_LINKER_FLAGS)
+  endif()
+endif()
 
 option(LLVM_BUILD_INSTRUMENTED_COVERAGE "Build LLVM and tools with Code Coverage instrumentation" Off)
 mark_as_advanced(LLVM_BUILD_INSTRUMENTED_COVERAGE)
 append_if(LLVM_BUILD_INSTRUMENTED_COVERAGE "-fprofile-instr-generate='${LLVM_PROFILE_FILE_PATTERN}' -fcoverage-mapping"
   CMAKE_CXX_FLAGS
   CMAKE_C_FLAGS
   CMAKE_EXE_LINKER_FLAGS
   CMAKE_SHARED_LINKER_FLAGS)