From 6c74a386ba460cb0e9a60c3d4dccdf65d68f9de5 Mon Sep 17 00:00:00 2001
From: Vassil Vassilev <v.g.vassilev@gmail.com>
Date: Wed, 28 Mar 2018 17:17:55 +0200
Subject: [PATCH] Enable ROOT to be built with prebuilt clang and llvm.

To do so one needs to pass -Dbuiltin_llvm=Off -Dbuiltin_clang=Off and the
PATH should contain the path to llvm-config.

Note this is not enabling ROOT to work with vanilla clang!

This patch allows ROOT to be built against a prebuilt clang and llvm from
https://root.cern.ch/git/{llvm.git,clang.git}. It allows to reduce ROOT's
build times (in cases when cmake decides to rebuild the in-tree llvm for
no good reason). It moves the common denominator of different ROOT builds
in one place to save space. It also allows easy switch between LLVM in
debug and release mode.

To build the external clang and llvm exactly in the same way as the
in-tree builds use:

CMAKE_FLAGS="\
            -DLLVM_ENABLE_WARNINGS=OFF                   \
            -DLLVM_INCLUDE_TESTS=OFF                     \
            -DCLANG_INCLUDE_TESTS=OFF                    \
            -DLLVM_INCLUDE_EXAMPLES=OFF                  \
            -DCLANG_BUILD_TOOLS=OFF                      \
            -DCLANG_TOOL_ARCMT_TEST_BUILD=OFF            \
            -DCLANG_TOOL_CLANG_CHECK_BUILD=OFF           \
            -DCLANG_TOOL_CLANG_FORMAT_BUILD=OFF          \
            -DCLANG_TOOL_CLANG_FORMAT_VS_BUILD=OFF       \
            -DCLANG_TOOL_CLANG_FUZZER_BUILD=OFF          \
            -DCLANG_TOOL_CLANG_IMPORT_TEST_BUILD=OFF     \
            -DCLANG_TOOL_CLANG_OFFLOAD_BUNDLER_BUILD=OFF \
            -DCLANG_TOOL_CLANG_RENAME_BUILD=OFF          \
            -DCLANG_TOOL_C_ARCMT_TEST_BUILD=OFF          \
            -DCLANG_TOOL_C_INDEX_TEST_BUILD=OFF          \
            -DCLANG_TOOL_DIAGTOOL_BUILD=OFF              \
            -DCLANG_TOOL_LIBCLANG_BUILD=OFF              \
            -DCLANG_TOOL_SCAN_BUILD_BUILD=OFF            \
            -DCLANG_TOOL_SCAN_VIEW_BUILD=OFF             \
            -DLLVM_BUILD_TOOLS=OFF                       \
            -DLLVM_TOOL_LLVM_AR_BUILD=OFF                \
            -DCLANG_TOOL_CLANG_OFFLOAD_BUNDLER_BUILD=OFF \
            -DLLVM_FORCE_USE_OLD_TOOLCHAIN=ON            \
            -DCLANG_ENABLE_STATIC_ANALYZER=OFF           \
            -DCLANG_ENABLE_ARCMT=OFF                     \
            -DCLANG_ENABLE_FORMAT=OFF                    \
            -DLLVM_TARGETS_TO_BUILD=host                 \
            -DLLVM_ABI_BREAKING_CHECKS=FORCE_OFF         \
            -DLLVM_ENABLE_ABI_BREAKING_CHECKS=OFF        \
            -DCMAKE_INSTALL_PREFIX=..                    \
            -DCMAKE_BUILD_TYPE=Debug"

cmake "$CMAKE_FLAGS"   ../../../sources/root-llvm/
---
 CMakeLists.txt                   |  4 +++-
 lib/Interpreter/CMakeLists.txt   | 14 +++++++-------
 lib/MetaProcessor/CMakeLists.txt |  3 ---
 3 files changed, 10 insertions(+), 11 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index a018497b..8afad4d1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -458,7 +458,9 @@ list(APPEND LLVM_COMMON_DEPENDS ${CLANG_TABLEGEN_TARGETS})
 if (TARGET intrinsics_gen)
   list(APPEND LLVM_COMMON_DEPENDS intrinsics_gen)
 endif()
-list(APPEND LLVM_COMMON_DEPENDS clang-headers)
+if (TARGET clang-headers)
+  list(APPEND LLVM_COMMON_DEPENDS clang-headers)
+endif()
 
 add_subdirectory(lib)
 add_subdirectory(tools)
diff --git a/lib/Interpreter/CMakeLists.txt b/lib/Interpreter/CMakeLists.txt
index c5a45340..9e23efe4 100644
--- a/lib/Interpreter/CMakeLists.txt
+++ b/lib/Interpreter/CMakeLists.txt
@@ -7,15 +7,17 @@
 #------------------------------------------------------------------------------
 
 set(LIBS
+  clangAnalysis
+  clangAST
+  clangBasic
+  clangCodeGen
   clangDriver
+  clangEdit
   clangFrontend
+  clangLex
   clangParse
   clangSema
-  clangAST
-  clangLex
   clangSerialization
-  clangCodeGen
-  clangBasic
 
   clingUtils
 )
@@ -23,6 +25,7 @@ set(LIBS
 set( LLVM_LINK_COMPONENTS
   analysis
   core
+  coverage
   executionengine
   ipo
   mc
@@ -73,9 +76,6 @@ add_cling_library(clingInterpreter OBJECT
   ValuePrinter.cpp
   ValuePrinterSynthesizer.cpp
 
-  DEPENDS
-  ClangDriverOptions
-
   LINK_LIBS
   ${LIBS}
 )
diff --git a/lib/MetaProcessor/CMakeLists.txt b/lib/MetaProcessor/CMakeLists.txt
index 35f67594..e753dca3 100644
--- a/lib/MetaProcessor/CMakeLists.txt
+++ b/lib/MetaProcessor/CMakeLists.txt
@@ -20,9 +20,6 @@ add_cling_library(clingMetaProcessor OBJECT
   MetaProcessor.cpp
   MetaSema.cpp
 
-  DEPENDS
-  ClangDriverOptions
-
   LINK_LIBS
   clangLex
   clangAST