[libc-commits] [libc] [libc] Add base for target config within cmake (PR #72318)

[via libc-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libc

Author: None (michaelrj-google)

<details>
<summary>Changes</summary>

Currently the only way to add or remove entrypoints is to modify the
entrypoints.txt file for the current target. This isn't ideal since
a user would have to carry a diff for this file when updating their
checkout. This patch adds a basic mechanism to allow the user to remove
entrypoints without modifying the repository. 


---
Full diff: https://github.com/llvm/llvm-project/pull/72318.diff


2 Files Affected:

- (modified) libc/CMakeLists.txt (+35-11) 
- (modified) libc/config/CMakeLists.txt (+2) 


``````````diff
diff --git a/libc/CMakeLists.txt b/libc/CMakeLists.txt
index 414be906336bf3f..4460820d86973b3 100644
--- a/libc/CMakeLists.txt
+++ b/libc/CMakeLists.txt
@@ -103,6 +103,8 @@ option(LLVM_LIBC_ENABLE_LINTING "Enables linting of libc source files" OFF)
 option(LIBC_GPU_BUILD "Build libc for the GPU. All CPU build options will be ignored." OFF)
 set(LIBC_TARGET_TRIPLE "" CACHE STRING "The target triple for the libc build.")
 
+option(LIBC_SYSTEM_CONFIG_FILE "The path to user provided cmake file that configures the build for the target system." OFF)
+
 set(LIBC_ENABLE_UNITTESTS ON)
 set(LIBC_ENABLE_HERMETIC_TESTS ${LLVM_LIBC_FULL_BUILD})
 
@@ -247,21 +249,43 @@ include(CMakeParseArguments)
 include(LLVMLibCCheckCpuFeatures)
 include(LLVMLibCRules)
 
-if(EXISTS "${LIBC_SOURCE_DIR}/config/${LIBC_TARGET_OS}/${LIBC_TARGET_ARCHITECTURE}/entrypoints.txt")
-  set(entrypoint_file "${LIBC_SOURCE_DIR}/config/${LIBC_TARGET_OS}/${LIBC_TARGET_ARCHITECTURE}/entrypoints.txt")
-elseif(EXISTS "${LIBC_SOURCE_DIR}/config/${LIBC_TARGET_OS}/entrypoints.txt")
-  set(entrypoint_file "${LIBC_SOURCE_DIR}/config/${LIBC_TARGET_OS}/entrypoints.txt")
+# If the user wants to provide their own list of entrypoints and headers
+if(LIBC_SYSTEM_CONFIG_FILE)
+  # Use the file provided by the user if it exists
+  if(EXISTS "${LIBC_SYSTEM_CONFIG_FILE}")
+    include("${LIBC_SYSTEM_CONFIG_FILE}")
+  else()
+    message(FATAL_ERROR "System Config File set to unavailable file '${LIBC_SYSTEM_CONFIG_FILE}'")
+  endif()
 else()
-  message(FATAL_ERROR "entrypoints.txt file for the target platform '${LIBC_TARGET_OS}/${LIBC_TARGET_ARCHITECTURE}' not found.")
-endif()
-include(${entrypoint_file})
+  # Else use the files in config/OS/CPU/ or config/OS/
+  if(EXISTS "${LIBC_SOURCE_DIR}/config/${LIBC_TARGET_OS}/${LIBC_TARGET_ARCHITECTURE}/entrypoints.txt")
+    set(entrypoint_file "${LIBC_SOURCE_DIR}/config/${LIBC_TARGET_OS}/${LIBC_TARGET_ARCHITECTURE}/entrypoints.txt")
+  elseif(EXISTS "${LIBC_SOURCE_DIR}/config/${LIBC_TARGET_OS}/entrypoints.txt")
+    set(entrypoint_file "${LIBC_SOURCE_DIR}/config/${LIBC_TARGET_OS}/entrypoints.txt")
+  else()
+    message(FATAL_ERROR "entrypoints.txt file for the target platform '${LIBC_TARGET_OS}/${LIBC_TARGET_ARCHITECTURE}' not found.")
+  endif()
+  include(${entrypoint_file})
 
-if(EXISTS "${LIBC_SOURCE_DIR}/config/${LIBC_TARGET_OS}/${LIBC_TARGET_ARCHITECTURE}/headers.txt")
-  include("${LIBC_SOURCE_DIR}/config/${LIBC_TARGET_OS}/${LIBC_TARGET_ARCHITECTURE}/headers.txt")
-elseif(EXISTS "${LIBC_SOURCE_DIR}/config/${LIBC_TARGET_OS}/headers.txt")
-  include("${LIBC_SOURCE_DIR}/config/${LIBC_TARGET_OS}/headers.txt")
+  if(EXISTS "${LIBC_SOURCE_DIR}/config/${LIBC_TARGET_OS}/${LIBC_TARGET_ARCHITECTURE}/headers.txt")
+    include("${LIBC_SOURCE_DIR}/config/${LIBC_TARGET_OS}/${LIBC_TARGET_ARCHITECTURE}/headers.txt")
+  elseif(EXISTS "${LIBC_SOURCE_DIR}/config/${LIBC_TARGET_OS}/headers.txt")
+    include("${LIBC_SOURCE_DIR}/config/${LIBC_TARGET_OS}/headers.txt")
+  endif()
 endif()
 
+# #TODO: Set up support for premade configs.
+
+# foreach(removed_entrypoint IN LISTS TARGET_LLVMLIBC_REMOVED_ENTRYPOINTS)
+#   if(LIBC_CMAKE_VERBOSE_LOGGING)
+#     message(STATUS "Removing entrypoint ${removed_entrypoint}")
+#   endif()
+#   list(REMOVE_ITEM TARGET_LLVMLIBC_ENTRYPOINTS ${removed_entrypoint})
+#   list(REMOVE_ITEM TARGET_LIBC_ENTRYPOINTS ${removed_entrypoint})
+#   list(REMOVE_ITEM TARGET_LIBM_ENTRYPOINTS ${removed_entrypoint})
+# endforeach()
+
 set(TARGET_ENTRYPOINT_NAME_LIST "")
 foreach(entrypoint IN LISTS TARGET_LLVMLIBC_ENTRYPOINTS)
   string(FIND ${entrypoint} "." last_dot_loc REVERSE)
diff --git a/libc/config/CMakeLists.txt b/libc/config/CMakeLists.txt
index a1034f9954740fe..853854b03be4e4e 100644
--- a/libc/config/CMakeLists.txt
+++ b/libc/config/CMakeLists.txt
@@ -1 +1,3 @@
+#TODO: Properly select the correct subdirectory.
+
 add_subdirectory(linux)

``````````

</details>


https://github.com/llvm/llvm-project/pull/72318