Add experimental support for unofficial monorepo-like directory layout

Summary:
This allows to have clang and llvm and the other subprojects
side-by-side instead of nested. This can be used with the monorepo or
multiple repos.

It will help having a single set of sources checked out but allows to
have a build directory with llvm and another one with llvm+clang.
Basically it abstracts LLVM_EXTERNAL_xxxx_SOURCE_DIR making it more
convenient by adopting a convention.

Reviewers: bogner, beanz, jlebar

Subscribers: mgorny, llvm-commits

Differential Revision: https://reviews.llvm.org/D26365

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@286162 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7a70ebc..9fcb30a 100644 (file)
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -93,6 +93,31 @@ if(CMAKE_HOST_APPLE AND APPLE)
   endif()
 endif()
 
+# Side-by-side subprojects layout: automatically set the
+# LLVM_EXTERNAL_${project}_SOURCE_DIR using LLVM_ALL_PROJECTS
+# This allows an easy way of setting up a build directory for llvm and another
+# one for llvm+clang+... using the same sources.
+set(LLVM_ALL_PROJECTS "clang;libcxx;libcxxabi;lldb;compiler-rt;lld;polly")
+set(LLVM_ENABLE_PROJECTS "" CACHE STRING
+       "Semicolon-separated list of projects to build (${LLVM_ALL_PROJECTS}), or \"all\".")
+if( LLVM_ENABLE_PROJECTS STREQUAL "all" )
+  set( LLVM_ENABLE_PROJECTS ${LLVM_ALL_PROJECTS})
+endif()
+foreach(proj ${LLVM_ENABLE_PROJECTS})
+  set(PROJ_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../${proj}")
+  if(NOT EXISTS "${PROJ_DIR}" OR NOT IS_DIRECTORY "${PROJ_DIR}")
+    message(FATAL_ERROR "LLVM_ENABLE_PROJECTS requests ${proj} but directory not found: ${PROJ_DIR}")
+  endif()
+  string(TOUPPER "${proj}" upper_proj)
+  set(LLVM_EXTERNAL_${upper_proj}_SOURCE_DIR   "${CMAKE_CURRENT_SOURCE_DIR}/../${proj}")
+  # There is a widely spread opinion that clang-tools-extra should be merged
+  # into clang. The following simulates it by always enabling clang-tools-extra
+  # when enabling clang.
+  if (proj STREQUAL "clang")
+    set(LLVM_EXTERNAL_CLANG_TOOLS_EXTRA_SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../clang-tools-extra")
+  endif()
+endforeach()
+
 # The following only works with the Ninja generator in CMake >= 3.0.
 set(LLVM_PARALLEL_COMPILE_JOBS "" CACHE STRING
   "Define the maximum number of concurrent compilation jobs.")

diff --git a/docs/CMake.rst b/docs/CMake.rst
index 7dc475b..b8a5b31 100644 (file)
--- a/docs/CMake.rst
+++ b/docs/CMake.rst
@@ -336,6 +336,14 @@ LLVM-specific variables
   will not be used.  If the variable for an external project does not point
   to a valid path, then that project will not be built.
 
+**LLVM_ENABLE_PROJECTS**:STRING
+  Semicolon-separated list of projects to build, or *all* for building all
+  (clang, libcxx, libcxxabi, lldb, compiler-rt, lld, polly) projects.
+  This flag assumes that projects are checked out side-by-side and not nested,
+  i.e. clang needs to be in parallel of llvm instead of nested in `llvm/tools`.
+  This feature allows to have one build for only LLVM and another for clang+llvm
+  using the same source checkout.
+
 **LLVM_EXTERNAL_PROJECTS**:STRING
   Semicolon-separated list of additional external projects to build as part of
   llvm. For each project LLVM_EXTERNAL_<NAME>_SOURCE_DIR have to be specified