CMake: Improve usage of llvm-config, esp. for consistent linking

This commit reworks the LLVM/Clang/LLD discovery process for CMake. The
biggest changes are that:
  1. We search for LLVM from most preferred directory to least, skipping
     any `llvm-config` that is the wrong version, or that doesn't
     support the requested link mode ("static" or "shared").
  2. `ZIG_PREFER_CLANG_CPP_DYLIB` has been renamed to `ZIG_SHARED_LLVM`,
     to better align with `ZIG_STATIC_LLVM`.
  3. We only search for LLVM and LLD in the same directory alongside LLVM.
  4. LLVM's link mode is forward to Clang, so that we can look for the
     appropriate shared/static libraries.
  5. We use `--static-libs` when querying `--system-libs` from llvm-config,
     so that this will include libz and other dependencies for
     statically linking LLD

Author: topolarity

CMakeLists.txt

@@ -66,11 +66,15 @@ endif()
 message(STATUS "Configuring zig version ${ZIG_VERSION}")
 
 set(ZIG_STATIC off CACHE BOOL "Attempt to build a static zig executable (not compatible with glibc)")
+set(ZIG_SHARED_LLVM off CACHE BOOL "Prefer linking against shared LLVM libraries")
 set(ZIG_STATIC_LLVM off CACHE BOOL "Prefer linking against static LLVM libraries")
 set(ZIG_STATIC_ZLIB off CACHE BOOL "Prefer linking against static zlib")
-set(ZIG_PREFER_CLANG_CPP_DYLIB off CACHE BOOL "Try to link against -lclang-cpp")
 set(ZIG_USE_CCACHE off CACHE BOOL "Use ccache if available")
 
+if (ZIG_SHARED_LLVM AND ZIG_STATIC_LLVM)
+    message(SEND_ERROR "-DZIG_SHARED_LLVM and -DZIG_STATIC_LLVM cannot both be enabled simultaneously")
+endif()
+
 if(CCACHE_PROGRAM AND ZIG_USE_CCACHE)
     SET_PROPERTY(GLOBAL PROPERTY RULE_LAUNCH_COMPILE "${CCACHE_PROGRAM}")
 endif()

cmake/Findclang.cmake

@@ -7,53 +7,29 @@
 # CLANG_LIBRARIES
 # CLANG_LIBDIRS
 
+#TODO: FIXME
 find_path(CLANG_INCLUDE_DIRS NAMES clang/Frontend/ASTUnit.h
-  PATHS
-    /usr/lib/llvm/14/include
-    /usr/lib/llvm-14/include
-    /usr/lib/llvm-14.0/include
-    /usr/local/llvm140/include
-    /usr/local/llvm14/include
-    /usr/local/opt/llvm@14/include
-    /opt/homebrew/opt/llvm@14/include
-    /mingw64/include
+  HINTS ${LLVM_INCLUDE_DIRS}
+  NO_DEFAULT_PATH # Only look for clang next to LLVM
 )
 
-if(ZIG_PREFER_CLANG_CPP_DYLIB)
+if(${LLVM_LINK_MODE} STREQUAL "shared")
   find_library(CLANG_LIBRARIES
     NAMES
+      libclang-cpp.so.14
       clang-cpp-14.0
       clang-cpp140
       clang-cpp
     NAMES_PER_DIR
-    PATHS
-      ${CLANG_LIBDIRS}
-      /usr/lib/llvm/14/lib
-      /usr/lib/llvm/14/lib64
-      /usr/lib/llvm-14/lib
-      /usr/local/llvm140/lib
-      /usr/local/llvm14/lib
-      /usr/local/opt/llvm@14/lib
-      /opt/homebrew/opt/llvm@14/lib
+    HINTS "${LLVM_LIBDIRS}"
+    NO_DEFAULT_PATH # Only look for Clang next to LLVM
   )
-endif()
-
-if(NOT CLANG_LIBRARIES)
+else()
   macro(FIND_AND_ADD_CLANG_LIB _libname_)
     string(TOUPPER ${_libname_} _prettylibname_)
     find_library(CLANG_${_prettylibname_}_LIB NAMES ${_libname_} NAMES_PER_DIR
-      PATHS
-        ${CLANG_LIBDIRS}
-        /usr/lib/llvm/14/lib
-        /usr/lib/llvm-14/lib
-        /usr/lib/llvm-14.0/lib
-        /usr/local/llvm140/lib
-        /usr/local/llvm14/lib
-        /usr/local/opt/llvm@14/lib
-        /opt/homebrew/opt/llvm@14/lib
-        /mingw64/lib
-        /c/msys64/mingw64/lib
-        c:\\msys64\\mingw64\\lib
+      HINTS "${LLVM_LIBDIRS}"
+      NO_DEFAULT_PATH # Only look for Clang next to LLVM
     )
     if(CLANG_${_prettylibname_}_LIB)
       set(CLANG_LIBRARIES ${CLANG_LIBRARIES} ${CLANG_${_prettylibname_}_LIB})

cmake/Findlld.cmake

@@ -7,40 +7,25 @@
 # LLD_LIBRARIES
 
 find_path(LLD_INCLUDE_DIRS NAMES lld/Common/Driver.h
-    PATHS
-        /usr/lib/llvm-14/include
-        /usr/local/llvm140/include
-        /usr/local/llvm14/include
-        /usr/local/opt/llvm@14/include
-        /opt/homebrew/opt/llvm@14/include
-        /mingw64/include)
+    HINTS ${LLVM_INCLUDE_DIRS}
+    NO_DEFAULT_PATH # Only look for LLD next to LLVM
+)
 
 find_library(LLD_LIBRARY NAMES lld-14.0 lld140 lld NAMES_PER_DIR
-    PATHS
-        /usr/lib/llvm-14/lib
-        /usr/local/llvm140/lib
-        /usr/local/llvm14/lib
-        /usr/local/opt/llvm@14/lib
-        /opt/homebrew/opt/llvm@14/lib
+    HINTS ${LLVM_LIBDIRS}
+    NO_DEFAULT_PATH # Only look for LLD next to LLVM
 )
 if(EXISTS ${LLD_LIBRARY})
     set(LLD_LIBRARIES ${LLD_LIBRARY})
 else()
     macro(FIND_AND_ADD_LLD_LIB _libname_)
         string(TOUPPER ${_libname_} _prettylibname_)
         find_library(LLD_${_prettylibname_}_LIB NAMES ${_libname_} NAMES_PER_DIR
-            PATHS
-                ${LLD_LIBDIRS}
-                /usr/lib/llvm-14/lib
-                /usr/local/llvm140/lib
-                /usr/local/llvm14/lib
-                /usr/local/opt/llvm@14/lib
-                /opt/homebrew/opt/llvm@14/lib
-                /mingw64/lib
-                /c/msys64/mingw64/lib
-                c:/msys64/mingw64/lib)
-            if(LLD_${_prettylibname_}_LIB)
-                set(LLD_LIBRARIES ${LLD_LIBRARIES} ${LLD_${_prettylibname_}_LIB})
+            HINTS ${LLVM_LIBDIRS}
+            NO_DEFAULT_PATH # Only look for LLD next to LLVM
+        )
+        if(LLD_${_prettylibname_}_LIB)
+            set(LLD_LIBRARIES ${LLD_LIBRARIES} ${LLD_${_prettylibname_}_LIB})
         endif()
     endmacro(FIND_AND_ADD_LLD_LIB)