[libc] Use a prebuilt libc-hdrgen binary if available.
This feature will primarily by used by the runtimes build. In the
runtimes build, we build libc-hdrgen once for the host and use it
to build the libc for other targets. So, the host libc-hdrgen is
like a prebuilt passed to the target builds.
Reviewed By: lntue
Differential Revision: https://reviews.llvm.org/D141426
diff --git a/libc/CMakeLists.txt b/libc/CMakeLists.txt
index 7bf1c02..a293286 100644
--- a/libc/CMakeLists.txt
+++ b/libc/CMakeLists.txt
@@ -14,10 +14,21 @@
# The top-level directory in which libc is being built.
set(LIBC_BUILD_DIR ${CMAKE_CURRENT_BINARY_DIR})
-# For a runtimes build we need to manually include tablgen and LLVM directories.
-if ("libc" IN_LIST LLVM_ENABLE_RUNTIMES)
- include(TableGen)
- set(LLVM_LIBC_INCLUDE_DIRS ${LLVM_MAIN_INCLUDE_DIR} ${LLVM_BINARY_DIR}/include)
+if(LLVM_LIBC_FULL_BUILD)
+ if(NOT LIBC_HDRGEN_EXE)
+ # We need to set up hdrgen first since other targets depend on it.
+ add_subdirectory(utils/LibcTableGenUtil)
+ add_subdirectory(utils/HdrGen)
+ else()
+ message(STATUS "Will use ${LIBC_HDRGEN_EXE} for libc header generation.")
+ endif()
+endif()
+
+if(LLVM_ENABLE_RUNTIMES AND NOT LLVM_RUNTIMES_BUILD)
+ # When libc is build as part of the runtimes/bootstrap build's CMake run, we
+ # only need to build the host tools to build the libc. So, we just do enough
+ # to build libc-hdrgen and return.
+ return()
endif()
# Path libc/scripts directory.
@@ -150,12 +161,6 @@
list(APPEND TARGET_ENTRYPOINT_NAME_LIST ${entrypoint_name})
endforeach()
-if(LLVM_LIBC_FULL_BUILD)
- # We need to set up hdrgen first since other targets depend on it.
- add_subdirectory(utils/LibcTableGenUtil)
- add_subdirectory(utils/HdrGen)
-endif()
-
set(LIBC_TARGET)
set(LIBC_COMPONENT)
set(LIBC_INSTALL_DEPENDS)
