[CMake] Cache the compiler-rt library search results

There's a lot of duplicated calls to find various compiler-rt libraries
from build of runtime libraries like libunwind, libc++, libc++abi and
compiler-rt. The compiler-rt helper module already implemented caching
for results avoid repeated Clang invocations.

This change moves the compiler-rt implementation into a shared location
and reuses it from other runtimes to reduce duplication and speed up
the build.

Differential Revision: https://reviews.llvm.org/D88458

1 files changed, 101 insertions, 0 deletions

diff --git a/cmake/Modules/HandleCompilerRT.cmake b/cmake/Modules/HandleCompilerRT.cmake
new file mode 100644
index 000000000000..00661d102c2a
--- /dev/null
+++ b/cmake/Modules/HandleCompilerRT.cmake
@@ -0,0 +1,101 @@
+# Check if compile-rt library file path exists.
+# If found, cache the path in:
+#    COMPILER_RT_LIBRARY-<name>-<target>
+# If err_flag is true OR path not found, emit a message and set:
+#    COMPILER_RT_LIBRARY-<name>-<target> to NOTFOUND
+function(cache_compiler_rt_library err_flag name target library_file)
+  if(err_flag OR NOT EXISTS "${library_file}")
+    message(STATUS "Failed to find compiler-rt ${name} library for ${target}")
+    set(COMPILER_RT_LIBRARY_${name}_${target} "NOTFOUND" CACHE INTERNAL
+        "compiler-rt ${name} library for ${target}")
+  else()
+    message(STATUS "Found compiler-rt ${name} library: ${library_file}")
+    set(COMPILER_RT_LIBRARY_${name}_${target} "${library_file}" CACHE INTERNAL
+        "compiler-rt ${name} library for ${target}")
+  endif()
+endfunction()
+
+function(get_component_name name variable)
+  if(APPLE)
+    if(NOT name MATCHES "builtins.*")
+      set(component_name "${name}_")
+    endif()
+    # TODO: Support ios, tvos and watchos as well.
+    set(component_name "${component_name}osx")
+  else()
+    set(component_name "${name}")
+  endif()
+  set(${variable} "${component_name}" PARENT_SCOPE)
+endfunction()
+
+# Find the path to compiler-rt library `name` (e.g. "builtins") for the
+# specified `TARGET` (e.g. "x86_64-linux-gnu") and return it in `variable`.
+# This calls cache_compiler_rt_library that caches the path to speed up
+# repeated invocations with the same `name` and `target`.
+function(find_compiler_rt_library name variable)
+  cmake_parse_arguments(ARG "" "TARGET" "" ${ARGN})
+  # While we can use compiler-rt runtimes with other compilers, we need to
+  # query the compiler for runtime location and thus we require Clang.
+  if(NOT CMAKE_CXX_COMPILER_ID MATCHES Clang)
+    set(${variable} "NOTFOUND" PARENT_SCOPE)
+    return()
+  endif()
+  set(target "${ARG_TARGET}")
+  if(NOT target AND CMAKE_CXX_COMPILER_TARGET)
+    set(target "${CMAKE_CXX_COMPILER_TARGET}")
+  endif()
+  if(NOT DEFINED COMPILER_RT_LIBRARY_builtins_${target})
+    # If the cache variable is not defined, invoke Clang and then
+    # set it with cache_compiler_rt_library.
+    set(clang_command ${CMAKE_CXX_COMPILER} ${CMAKE_REQUIRED_FLAGS})
+    if(target)
+      list(APPEND clang_command "--target=${target}")
+    endif()
+    get_property(cxx_flags CACHE CMAKE_CXX_FLAGS PROPERTY VALUE)
+    string(REPLACE " " ";" cxx_flags "${cxx_flags}")
+    list(APPEND clang_command ${cxx_flags})
+    execute_process(
+      COMMAND ${clang_command} "--rtlib=compiler-rt" "-print-libgcc-file-name"
+      RESULT_VARIABLE had_error
+      OUTPUT_VARIABLE library_file
+    )
+    string(STRIP "${library_file}" library_file)
+    file(TO_CMAKE_PATH "${library_file}" library_file)
+    get_filename_component(dirname ${library_file} DIRECTORY)
+    if(APPLE)
+      execute_process(
+        COMMAND ${clang_command} "--print-resource-dir"
+        RESULT_VARIABLE had_error
+        OUTPUT_VARIABLE resource_dir
+      )
+      string(STRIP "${resource_dir}" resource_dir)
+      set(dirname "${resource_dir}/lib/darwin")
+    endif()
+    get_filename_component(basename ${library_file} NAME)
+    if(basename MATCHES "libclang_rt\.([a-z0-9_\-]+)\.a")
+      set(from_name ${CMAKE_MATCH_1})
+      get_component_name(${CMAKE_MATCH_1} to_name)
+      string(REPLACE "${from_name}" "${to_name}" basename "${basename}")
+      set(library_file "${dirname}/${basename}")
+      cache_compiler_rt_library(${had_error} builtins "${target}" "${library_file}")
+    endif()
+  endif()
+  if(NOT COMPILER_RT_LIBRARY_builtins_${target})
+    set(${variable} "NOTFOUND" PARENT_SCOPE)
+    return()
+  endif()
+  if(NOT DEFINED COMPILER_RT_LIBRARY_${name}_${target})
+    # Clang gives only the builtins library path. Other library paths are
+    # obtained by substituting "builtins" with ${name} in the builtins
+    # path and then checking if the resultant path exists. The result of
+    # this check is also cached by cache_compiler_rt_library.
+    set(library_file "${COMPILER_RT_LIBRARY_builtins_${target}}")
+    if(library_file MATCHES ".*libclang_rt\.([a-z0-9_\-]+)\.a")
+      set(from_name ${CMAKE_MATCH_0})
+      get_component_name(${name} to_name)
+      string(REPLACE "${from_name}" "${to_name}" library_file "${library_file}")
+      cache_compiler_rt_library(FALSE "${name}" "${target}" "${library_file}")
+    endif()
+  endif()
+  set(${variable} "${COMPILER_RT_LIBRARY_${name}_${target}}" PARENT_SCOPE)
+endfunction()