[Offload] Don't check in generated files (#141982)

Previously we decided to check in files that we generate with tablegen.
The justification at the time was that it helped reviewers unfamiliar
with `offload-tblgen` see the actual changes to the headers in PRs.
After trying it for a while, it's ended up causing some headaches and is
also not how tablegen is used elsewhere in LLVM.

This changes our use of tablegen to be more conventional. Where
possible, files are still clang-formatted, but this is no longer a hard
requirement. Because `OffloadErrcodes.inc` is shared with libomptarget
it now gets generated in a more appropriate place.

Author: callumfare

offload/CMakeLists.txt

@@ -363,6 +363,8 @@ set(LIBOMPTARGET_LLVM_LIBRARY_DIR "${LLVM_LIBRARY_DIR}" CACHE STRING
 set(LIBOMPTARGET_LLVM_LIBRARY_INTDIR "${LIBOMPTARGET_INTDIR}" CACHE STRING
   "Path to folder where intermediate libraries will be output")
 
+add_subdirectory(tools/offload-tblgen)
+
 # Build offloading plugins and device RTLs if they are available.
 add_subdirectory(plugins-nextgen)
 add_subdirectory(DeviceRTL)
@@ -371,7 +373,6 @@ add_subdirectory(tools)
 # Build target agnostic offloading library.
 add_subdirectory(libomptarget)
 
-add_subdirectory(tools/offload-tblgen)
 add_subdirectory(liboffload)
 
 # Add tests.

offload/include/Shared/OffloadErrcodes.inc

@@ -1,29 +1,46 @@
-# The OffloadGenerate target is used to regenerate the generated files in the
-# include directory. These files are checked in with the rest of the source,
-# therefore it is only needed when making changes to the API.
+# We want to clang-format the generated files if possible, since OffloadAPI.h is
+# the main public header for liboffload. Generate them in a temporary location,
+# then clang-format and copy them to the proper location. If clang-format is
+# missing just copy them.
+# Ideally we'd just clang-format them in place and avoid the copy but cmake
+# gets confused about the same path being a byproduct of two custom commands.
 
-find_program(CLANG_FORMAT clang-format PATHS ${LLVM_TOOLS_BINARY_DIR} NO_DEFAULT_PATH)
-if (CLANG_FORMAT)
-    set(LLVM_TARGET_DEFINITIONS ${CMAKE_CURRENT_SOURCE_DIR}/OffloadAPI.td)
+set(LLVM_TARGET_DEFINITIONS ${CMAKE_CURRENT_SOURCE_DIR}/OffloadAPI.td)
+set(files_to_copy "")
 
-    tablegen(OFFLOAD OffloadAPI.h -gen-api)
-    tablegen(OFFLOAD OffloadEntryPoints.inc -gen-entry-points)
-    tablegen(OFFLOAD OffloadFuncs.inc -gen-func-names)
-    tablegen(OFFLOAD OffloadImplFuncDecls.inc -gen-impl-func-decls)
-    tablegen(OFFLOAD OffloadPrint.hpp -gen-print-header)
-    tablegen(OFFLOAD OffloadErrcodes.inc -gen-errcodes)
+macro(offload_tablegen file)
+    tablegen(OFFLOAD generated/${file}.gen ${ARGN})
+    list(APPEND files_to_copy ${file})
+endmacro()
 
-    set(FILES_TO_COPY "OffloadAPI.h;OffloadEntryPoints.inc;OffloadFuncs.inc;OffloadImplFuncDecls.inc;OffloadPrint.hpp")
-    set(GEN_DIR ${CMAKE_CURRENT_SOURCE_DIR}/../include/generated)
-    add_public_tablegen_target(OffloadGenerate)
-    add_custom_command(TARGET OffloadGenerate POST_BUILD COMMAND ${CLANG_FORMAT}
-        -i ${TABLEGEN_OUTPUT})
-    add_custom_command(TARGET OffloadGenerate POST_BUILD COMMAND ${CMAKE_COMMAND}
-        -E copy_if_different ${FILES_TO_COPY} ${GEN_DIR})
-    add_custom_command(TARGET OffloadGenerate POST_BUILD COMMAND ${CMAKE_COMMAND}
-        -E copy_if_different OffloadErrcodes.inc "${LIBOMPTARGET_INCLUDE_DIR}/Shared/OffloadErrcodes.inc")
+offload_tablegen(OffloadAPI.h -gen-api)
+offload_tablegen(OffloadEntryPoints.inc -gen-entry-points)
+offload_tablegen(OffloadFuncs.inc -gen-func-names)
+offload_tablegen(OffloadImplFuncDecls.inc -gen-impl-func-decls)
+offload_tablegen(OffloadPrint.hpp -gen-print-header)
+
+add_public_tablegen_target(OffloadGenerate)
+
+add_custom_target(OffloadAPI DEPENDS OffloadGenerate)
+find_program(clang_format clang-format PATHS ${LLVM_TOOLS_BINARY_DIR} NO_DEFAULT_PATH)
+if (clang_format)
+    foreach(file IN LISTS files_to_copy)
+      add_custom_command(
+          OUTPUT ${file}
+          COMMAND ${clang_format} -i generated/${file}.gen
+          COMMAND ${CMAKE_COMMAND} -E copy_if_different generated/${file}.gen ${CMAKE_CURRENT_BINARY_DIR}/${file}
+          DEPENDS generated/${file}.gen
+      )
+      add_custom_target(OffloadAPI.${file} DEPENDS ${file})
+      add_dependencies(OffloadAPI OffloadAPI.${file})
+    endforeach()
 else()
-    message(WARNING "clang-format was not found, so the OffloadGenerate target\
-        will not be available. Offload will still build, but you will not be\
-        able to make changes to the API.")
+    message(WARNING "clang-format not found, the generated Offload API headers will not be formatted")
+    foreach(file IN LISTS files_to_copy)
+        add_custom_command(
+            OUTPUT ${file}
+            COMMAND ${CMAKE_COMMAND} -E copy_if_different generated/${file}.gen ${CMAKE_CURRENT_BINARY_DIR}/${file}
+            DEPENDS generated/${file}.gen
+        )
+    endforeach()
 endif()

offload/liboffload/API/CMakeLists.txt

@@ -8,6 +8,10 @@ add_llvm_library(
   LINK_COMPONENTS
   FrontendOpenMP
   Support
+
+  DEPENDS
+  OffloadAPI
+  PluginErrcodes
   )
 
 foreach(plugin IN LISTS LIBOMPTARGET_PLUGINS_TO_BUILD)
@@ -19,11 +23,13 @@ if(LLVM_HAVE_LINK_VERSION_SCRIPT)
 endif()
 
 target_include_directories(LLVMOffload PUBLIC
+                            ${CMAKE_CURRENT_BINARY_DIR}/API
                             ${CMAKE_CURRENT_BINARY_DIR}/../include
                             ${CMAKE_CURRENT_SOURCE_DIR}/include
-                            ${CMAKE_CURRENT_SOURCE_DIR}/include/generated
                             ${CMAKE_CURRENT_SOURCE_DIR}/../include
-                            ${CMAKE_CURRENT_SOURCE_DIR}/../plugins-nextgen/common/include)
+                            ${CMAKE_CURRENT_SOURCE_DIR}/../plugins-nextgen/common/include
+                            ${CMAKE_CURRENT_BINARY_DIR}/../plugins-nextgen/common/include
+                            )
 
 target_compile_options(LLVMOffload PRIVATE ${offload_compile_flags})
 target_link_options(LLVMOffload PRIVATE ${offload_link_flags})
@@ -39,5 +45,5 @@ set_target_properties(LLVMOffload PROPERTIES
                       BUILD_RPATH "$ORIGIN:${CMAKE_CURRENT_BINARY_DIR}/..")
 install(TARGETS LLVMOffload LIBRARY COMPONENT LLVMOffload DESTINATION "${OFFLOAD_INSTALL_LIBDIR}")
 
-install(FILES ${CMAKE_CURRENT_SOURCE_DIR}/include/generated/OffloadAPI.h DESTINATION ${CMAKE_INSTALL_PREFIX}/include/offload)
-install(FILES ${CMAKE_CURRENT_SOURCE_DIR}/include/generated/OffloadPrint.hpp DESTINATION ${CMAKE_INSTALL_PREFIX}/include/offload)
+install(FILES ${CMAKE_CURRENT_BINARY_DIR}/API/OffloadAPI.h DESTINATION ${CMAKE_INSTALL_PREFIX}/include/offload)
+install(FILES ${CMAKE_CURRENT_BINARY_DIR}/API/OffloadPrint.hpp DESTINATION ${CMAKE_INSTALL_PREFIX}/include/offload)