[cmake] Move HandleOutOfTreeLLVM to common cmake utils

This is better than libunwind and libcxxabi fishing it out of libcxx's
module directory.

It is done in prepartion for a better version of D117537 which deduplicates
CMake logic instead of just renaming to avoid a name clash.

Reviewed By: phosek, #libunwind, #libc_abi, Ericson2314

Differential Revision: https://reviews.llvm.org/D117617

1 files changed, 80 insertions, 0 deletions

diff --git a/cmake/Modules/HandleOutOfTreeLLVM.cmake b/cmake/Modules/HandleOutOfTreeLLVM.cmake
new file mode 100644
index 000000000000..edffe572e091
--- /dev/null
+++ b/cmake/Modules/HandleOutOfTreeLLVM.cmake
@@ -0,0 +1,80 @@
+if (NOT DEFINED LLVM_PATH)
+  set(LLVM_PATH ${CMAKE_CURRENT_LIST_DIR}/../../llvm CACHE PATH "" FORCE)
+endif()
+
+if(NOT IS_DIRECTORY ${LLVM_PATH})
+  message(FATAL_ERROR
+    "The provided LLVM_PATH (${LLVM_PATH}) is not a valid directory. Note that "
+    "building libc++ outside of the monorepo is not supported anymore. Please "
+    "use a Standalone build against the monorepo, a Runtimes build or a classic "
+    "monorepo build.")
+endif()
+
+set(LLVM_INCLUDE_DIR ${LLVM_PATH}/include CACHE PATH "Path to llvm/include")
+set(LLVM_PATH ${LLVM_PATH} CACHE PATH "Path to LLVM source tree")
+set(LLVM_MAIN_SRC_DIR ${LLVM_PATH})
+set(LLVM_CMAKE_DIR "${LLVM_PATH}/cmake/modules")
+set(LLVM_BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR})
+set(LLVM_LIBRARY_OUTPUT_INTDIR "${CMAKE_CURRENT_BINARY_DIR}/lib")
+
+if (EXISTS "${LLVM_CMAKE_DIR}")
+  list(APPEND CMAKE_MODULE_PATH "${LLVM_CMAKE_DIR}")
+elseif (EXISTS "${LLVM_MAIN_SRC_DIR}/cmake/modules")
+  list(APPEND CMAKE_MODULE_PATH "${LLVM_MAIN_SRC_DIR}/cmake/modules")
+else()
+  message(FATAL_ERROR "Neither ${LLVM_CMAKE_DIR} nor ${LLVM_MAIN_SRC_DIR}/cmake/modules found. "
+                      "This is not a supported configuration.")
+endif()
+
+message(STATUS "Configuring for standalone build.")
+
+# By default, we target the host, but this can be overridden at CMake invocation time.
+include(GetHostTriple)
+get_host_triple(LLVM_INFERRED_HOST_TRIPLE)
+set(LLVM_HOST_TRIPLE "${LLVM_INFERRED_HOST_TRIPLE}" CACHE STRING "Host on which LLVM binaries will run")
+set(LLVM_DEFAULT_TARGET_TRIPLE "${LLVM_HOST_TRIPLE}" CACHE STRING "Target triple used by default.")
+
+# Add LLVM Functions --------------------------------------------------------
+if (WIN32)
+  set(LLVM_ON_UNIX 0)
+  set(LLVM_ON_WIN32 1)
+else()
+  set(LLVM_ON_UNIX 1)
+  set(LLVM_ON_WIN32 0)
+endif()
+
+include(AddLLVM OPTIONAL)
+
+# LLVM Options --------------------------------------------------------------
+if (NOT DEFINED LLVM_INCLUDE_TESTS)
+  set(LLVM_INCLUDE_TESTS ON)
+endif()
+if (NOT DEFINED LLVM_INCLUDE_DOCS)
+  set(LLVM_INCLUDE_DOCS ON)
+endif()
+if (NOT DEFINED LLVM_ENABLE_SPHINX)
+  set(LLVM_ENABLE_SPHINX OFF)
+endif()
+
+if (LLVM_INCLUDE_TESTS)
+  # Required LIT Configuration ------------------------------------------------
+  # Define the default arguments to use with 'lit', and an option for the user
+  # to override.
+  set(LLVM_DEFAULT_EXTERNAL_LIT "${LLVM_MAIN_SRC_DIR}/utils/lit/lit.py")
+  set(LIT_ARGS_DEFAULT "-sv --show-xfail --show-unsupported")
+  if (MSVC OR XCODE)
+    set(LIT_ARGS_DEFAULT "${LIT_ARGS_DEFAULT} --no-progress-bar")
+  endif()
+  set(LLVM_LIT_ARGS "${LIT_ARGS_DEFAULT}" CACHE STRING "Default options for lit")
+endif()
+
+# Required doc configuration
+if (LLVM_ENABLE_SPHINX)
+  find_package(Sphinx REQUIRED)
+endif()
+
+if (LLVM_ON_UNIX AND NOT APPLE)
+  set(LLVM_HAVE_LINK_VERSION_SCRIPT 1)
+else()
+  set(LLVM_HAVE_LINK_VERSION_SCRIPT 0)
+endif()