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 in the same directory alongside LLVM.
  4. LLVM's link mode is forwarded to Clang, so that we can look for the
     appropriate shared/static libraries.
  5. We use `--link-static` when querying `--system-libs` from llvm-config,
     so that this will include libz and other dependencies for
     statically linking LLD

CMakeLists.txt

@@ -66,9 +66,9 @@ 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(CCACHE_PROGRAM AND ZIG_USE_CCACHE)
@@ -80,6 +80,10 @@ if(ZIG_STATIC)
     set(ZIG_STATIC_ZLIB ON)
 endif()
 
+if (ZIG_SHARED_LLVM AND ZIG_STATIC_LLVM)
+    message(SEND_ERROR "-DZIG_SHARED_LLVM and -DZIG_STATIC_LLVM cannot both be enabled simultaneously")
+endif()
+
 string(REGEX REPLACE "\\\\" "\\\\\\\\" ZIG_LIBC_LIB_DIR_ESCAPED "${ZIG_LIBC_LIB_DIR}")
 string(REGEX REPLACE "\\\\" "\\\\\\\\" ZIG_LIBC_STATIC_LIB_DIR_ESCAPED "${ZIG_LIBC_STATIC_LIB_DIR}")
 string(REGEX REPLACE "\\\\" "\\\\\\\\" ZIG_LIBC_INCLUDE_DIR_ESCAPED "${ZIG_LIBC_INCLUDE_DIR}")

cmake/Findclang.cmake

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

cmake/Findlld.cmake

@@ -7,21 +7,13 @@
 # LLD_LIBRARIES
 
 find_path(LLD_INCLUDE_DIRS NAMES lld/Common/Driver.h
-    PATHS
+    HINTS ${LLVM_INCLUDE_DIRS}
-        /usr/lib/llvm-14/include
+    NO_DEFAULT_PATH # Only look for LLD next to LLVM
-        /usr/local/llvm140/include
+)
-        /usr/local/llvm14/include
-        /usr/local/opt/llvm@14/include
-        /opt/homebrew/opt/llvm@14/include
-        /mingw64/include)
 
 find_library(LLD_LIBRARY NAMES lld-14.0 lld140 lld NAMES_PER_DIR
-    PATHS
+    HINTS ${LLVM_LIBDIRS}
-        /usr/lib/llvm-14/lib
+    NO_DEFAULT_PATH # Only look for LLD next to LLVM
-        /usr/local/llvm140/lib
-        /usr/local/llvm14/lib
-        /usr/local/opt/llvm@14/lib
-        /opt/homebrew/opt/llvm@14/lib
 )
 if(EXISTS ${LLD_LIBRARY})
     set(LLD_LIBRARIES ${LLD_LIBRARY})
@@ -29,16 +21,9 @@ else()
     macro(FIND_AND_ADD_LLD_LIB _libname_)
         string(TOUPPER ${_libname_} _prettylibname_)
         find_library(LLD_${_prettylibname_}_LIB NAMES ${_libname_} NAMES_PER_DIR
-            PATHS
+            HINTS ${LLVM_LIBDIRS}
-                ${LLD_LIBDIRS}
+            NO_DEFAULT_PATH # Only look for LLD next to LLVM
-                /usr/lib/llvm-14/lib
+        )
-                /usr/local/llvm140/lib
-                /usr/local/llvm14/lib
-                /usr/local/opt/llvm@14/lib
-                /opt/homebrew/opt/llvm@14/lib
-                /mingw64/lib
-                /c/msys64/mingw64/lib
-                c:/msys64/mingw64/lib)
         if(LLD_${_prettylibname_}_LIB)
             set(LLD_LIBRARIES ${LLD_LIBRARIES} ${LLD_${_prettylibname_}_LIB})
         endif()

cmake/Findllvm.cmake

@@ -6,40 +6,12 @@
 # LLVM_INCLUDE_DIRS
 # LLVM_LIBRARIES
 # LLVM_LIBDIRS
+# LLVM_LINK_MODE
 
-find_path(LLVM_INCLUDE_DIRS NAMES llvm/IR/IRBuilder.h
-  PATHS
-    /usr/lib/llvm/14/include
-    /usr/lib/llvm-14/include
-    /usr/lib/llvm-14.0/include
-    /usr/lib/llvm14/include
-    /usr/local/llvm14/include
-    /usr/local/llvm140/include
-    /usr/local/opt/llvm@14/include
-    /opt/homebrew/opt/llvm@14/include
-    /mingw64/include
-)
-
-if(ZIG_PREFER_CLANG_CPP_DYLIB)
-  find_library(LLVM_LIBRARIES
-    NAMES
-      LLVM-14.0
-      LLVM-14
-      LLVM-140
-      LLVM
-    NAMES_PER_DIR
-    PATHS
-      ${LLVM_LIBDIRS}
-      /usr/lib/llvm/14/lib
-      /usr/lib/llvm/14/lib64
-      /usr/lib/llvm-14/lib
-      /usr/lib/llvm14/lib
-      /usr/local/llvm14/lib
-      /usr/local/llvm140/lib
-      /usr/local/opt/llvm@14/lib
-      /opt/homebrew/opt/llvm@14/lib
-  )
 
+if(ZIG_USE_LLVM_CONFIG)
+  while(1)
+    unset(LLVM_CONFIG_EXE CACHE)
     find_program(LLVM_CONFIG_EXE
         NAMES llvm-config-14 llvm-config-14.0 llvm-config140 llvm-config14 llvm-config NAMES_PER_DIR
         PATHS
@@ -49,57 +21,55 @@ if(ZIG_PREFER_CLANG_CPP_DYLIB)
             "C:/Libraries/llvm-14.0.0/bin")
 
     if ("${LLVM_CONFIG_EXE}" STREQUAL "LLVM_CONFIG_EXE-NOTFOUND")
+      if (DEFINED LLVM_CONFIG_ERROR_MESSAGE)
+        message(FATAL_ERROR ${LLVM_CONFIG_ERROR_MESSAGE})
+      else()
         message(FATAL_ERROR "unable to find llvm-config")
       endif()
-
-  if ("${LLVM_CONFIG_EXE}" STREQUAL "LLVM_CONFIG_EXE-NOTFOUND")
-    message(FATAL_ERROR "unable to find llvm-config")
     endif()
 
+    # Check that this LLVM is the right version
     execute_process(
       COMMAND ${LLVM_CONFIG_EXE} --version
       OUTPUT_VARIABLE LLVM_CONFIG_VERSION
       OUTPUT_STRIP_TRAILING_WHITESPACE)
 
-  if("${LLVM_CONFIG_VERSION}" VERSION_LESS 14)
+    get_filename_component(LLVM_CONFIG_DIR "${LLVM_CONFIG_EXE}" DIRECTORY)
-    message(FATAL_ERROR "expected LLVM 14.x but found ${LLVM_CONFIG_VERSION} using ${LLVM_CONFIG_EXE}")
+    if("${LLVM_CONFIG_VERSION}" VERSION_LESS 14 OR "${LLVM_CONFIG_VERSION}" VERSION_EQUAL 15 OR "${LLVM_CONFIG_VERSION}" VERSION_GREATER 15)
-  endif()
+      # Save the error message, in case this is the last llvm-config we find
-  if("${LLVM_CONFIG_VERSION}" VERSION_EQUAL 15)
+      set(LLVM_CONFIG_ERROR_MESSAGE "expected LLVM 14.x but found ${LLVM_CONFIG_VERSION} using ${LLVM_CONFIG_EXE}")
-    message(FATAL_ERROR "expected LLVM 14.x but found ${LLVM_CONFIG_VERSION} using ${LLVM_CONFIG_EXE}")
-  endif()
-  if("${LLVM_CONFIG_VERSION}" VERSION_GREATER 15)
-    message(FATAL_ERROR "expected LLVM 14.x but found ${LLVM_CONFIG_VERSION} using ${LLVM_CONFIG_EXE}")
-  endif()
-elseif(ZIG_USE_LLVM_CONFIG)
-  find_program(LLVM_CONFIG_EXE
-      NAMES llvm-config-14 llvm-config-14.0 llvm-config140 llvm-config14 llvm-config NAMES_PER_DIR
-      PATHS
-          "/mingw64/bin"
-          "/c/msys64/mingw64/bin"
-          "c:/msys64/mingw64/bin"
-          "C:/Libraries/llvm-14.0.0/bin")
 
-  if ("${LLVM_CONFIG_EXE}" STREQUAL "LLVM_CONFIG_EXE-NOTFOUND")
+      # Ignore this directory and try the search again
-    message(FATAL_ERROR "unable to find llvm-config")
+      list(APPEND CMAKE_IGNORE_PATH "${LLVM_CONFIG_DIR}")
+      continue()
     endif()
 
-  if ("${LLVM_CONFIG_EXE}" STREQUAL "LLVM_CONFIG_EXE-NOTFOUND")
+    # Check that this LLVM supports linking as a shared/static library, if requested
-    message(FATAL_ERROR "unable to find llvm-config")
+    if (ZIG_SHARED_LLVM OR ZIG_STATIC_LLVM)
+      if (ZIG_SHARED_LLVM)
+        set(STATIC_OR_SHARED_LINK "--link-shared")
+      elseif (ZIG_STATIC_LLVM)
+        set(STATIC_OR_SHARED_LINK "--link-static")
       endif()
 
       execute_process(
-    COMMAND ${LLVM_CONFIG_EXE} --version
+        COMMAND ${LLVM_CONFIG_EXE} --libs ${STATIC_OR_SHARED_LINK}
-    OUTPUT_VARIABLE LLVM_CONFIG_VERSION
+        OUTPUT_QUIET
+        ERROR_VARIABLE LLVM_CONFIG_ERROR
         OUTPUT_STRIP_TRAILING_WHITESPACE)
 
-  if("${LLVM_CONFIG_VERSION}" VERSION_LESS 14)
+      if (LLVM_CONFIG_ERROR) 
-    message(FATAL_ERROR "expected LLVM 14.x but found ${LLVM_CONFIG_VERSION} using ${LLVM_CONFIG_EXE}")
+        # Save the error message, in case this is the last llvm-config we find
+        if (ZIG_SHARED_LLVM)
+          set(LLVM_CONFIG_ERROR_MESSAGE "LLVM 14.x found at ${LLVM_CONFIG_EXE} does not support linking as a shared library")
+        else()
+          set(LLVM_CONFIG_ERROR_MESSAGE "LLVM 14.x found at ${LLVM_CONFIG_EXE} does not support linking as a static library")
         endif()
-  if("${LLVM_CONFIG_VERSION}" VERSION_EQUAL 15)
+
-    message(FATAL_ERROR "expected LLVM 14.x but found ${LLVM_CONFIG_VERSION} using ${LLVM_CONFIG_EXE}")
+        # Ignore this directory and try the search again
+        list(APPEND CMAKE_IGNORE_PATH "${LLVM_CONFIG_DIR}")
+        continue()
       endif()
-  if("${LLVM_CONFIG_VERSION}" VERSION_GREATER 15)
-    message(FATAL_ERROR "expected LLVM 14.x but found ${LLVM_CONFIG_VERSION} using ${LLVM_CONFIG_EXE}")
     endif()
 
     execute_process(
@@ -110,7 +80,12 @@ elseif(ZIG_USE_LLVM_CONFIG)
     function(NEED_TARGET TARGET_NAME)
       list (FIND LLVM_TARGETS_BUILT "${TARGET_NAME}" _index)
       if (${_index} EQUAL -1)
-          message(FATAL_ERROR "LLVM (according to ${LLVM_CONFIG_EXE}) is missing target ${TARGET_NAME}. Zig requires LLVM to be built with all default targets enabled.")
+        # Save the error message, in case this is the last llvm-config we find
+        set(LLVM_CONFIG_ERROR_MESSAGE "LLVM (according to ${LLVM_CONFIG_EXE}) is missing target ${TARGET_NAME}. Zig requires LLVM to be built with all default targets enabled.")
+
+        # Ignore this directory and try the search again
+        list(APPEND CMAKE_IGNORE_PATH "${LLVM_CONFIG_DIR}")
+        continue()
       endif()
     endfunction(NEED_TARGET)
     NEED_TARGET("AArch64")
@@ -132,49 +107,68 @@ elseif(ZIG_USE_LLVM_CONFIG)
     NEED_TARGET("X86")
     NEED_TARGET("XCore")
 
-  if(ZIG_STATIC_LLVM)
+    # Got it!
+    break()
+  endwhile()
+
+  if(ZIG_SHARED_LLVM OR ZIG_STATIC_LLVM)
     execute_process(
-        COMMAND ${LLVM_CONFIG_EXE} --libfiles --link-static
+        COMMAND ${LLVM_CONFIG_EXE} --libfiles ${STATIC_OR_SHARED_LINK}
         OUTPUT_VARIABLE LLVM_LIBRARIES_SPACES
         OUTPUT_STRIP_TRAILING_WHITESPACE)
     string(REPLACE " " ";" LLVM_LIBRARIES "${LLVM_LIBRARIES_SPACES}")
 
     execute_process(
-        COMMAND ${LLVM_CONFIG_EXE} --system-libs --link-static
+        COMMAND ${LLVM_CONFIG_EXE} --libdir ${STATIC_OR_SHARED_LINK}
-        OUTPUT_VARIABLE LLVM_SYSTEM_LIBS_SPACES
-        OUTPUT_STRIP_TRAILING_WHITESPACE)
-    string(REPLACE " " ";" LLVM_SYSTEM_LIBS "${LLVM_SYSTEM_LIBS_SPACES}")
-
-    execute_process(
-        COMMAND ${LLVM_CONFIG_EXE} --libdir --link-static
         OUTPUT_VARIABLE LLVM_LIBDIRS_SPACES
         OUTPUT_STRIP_TRAILING_WHITESPACE)
     string(REPLACE " " ";" LLVM_LIBDIRS "${LLVM_LIBDIRS_SPACES}")
-  endif()
+
-  if(NOT LLVM_LIBRARIES)
+    execute_process(
+      COMMAND ${LLVM_CONFIG_EXE} --shared-mode ${STATIC_OR_SHARED_LINK}
+      OUTPUT_VARIABLE LLVM_LINK_MODE
+      OUTPUT_STRIP_TRAILING_WHITESPACE)
+  else()
     execute_process(
         COMMAND ${LLVM_CONFIG_EXE} --libs
         OUTPUT_VARIABLE LLVM_LIBRARIES_SPACES
         OUTPUT_STRIP_TRAILING_WHITESPACE)
     string(REPLACE " " ";" LLVM_LIBRARIES "${LLVM_LIBRARIES_SPACES}")
 
-    execute_process(
-        COMMAND ${LLVM_CONFIG_EXE} --system-libs
-        OUTPUT_VARIABLE LLVM_SYSTEM_LIBS_SPACES
-        OUTPUT_STRIP_TRAILING_WHITESPACE)
-    string(REPLACE " " ";" LLVM_SYSTEM_LIBS "${LLVM_SYSTEM_LIBS_SPACES}")
-
     execute_process(
         COMMAND ${LLVM_CONFIG_EXE} --libdir
         OUTPUT_VARIABLE LLVM_LIBDIRS_SPACES
         OUTPUT_STRIP_TRAILING_WHITESPACE)
     string(REPLACE " " ";" LLVM_LIBDIRS "${LLVM_LIBDIRS_SPACES}")
+
+    execute_process(
+      COMMAND ${LLVM_CONFIG_EXE} --shared-mode
+      OUTPUT_VARIABLE LLVM_LINK_MODE
+      OUTPUT_STRIP_TRAILING_WHITESPACE)
   endif()
 
+  # We always ask for the system libs corresponding to static linking,
+  # since we always statically link LLD which needs these libraries
+  execute_process(
+      COMMAND ${LLVM_CONFIG_EXE} --system-libs --link-static
+      OUTPUT_VARIABLE LLVM_SYSTEM_LIBS_SPACES
+      OUTPUT_STRIP_TRAILING_WHITESPACE)
+  string(REPLACE " " ";" LLVM_SYSTEM_LIBS "${LLVM_SYSTEM_LIBS_SPACES}")
+
   set(LLVM_LIBRARIES ${LLVM_LIBRARIES} ${LLVM_SYSTEM_LIBS})
 
+  execute_process(
+      COMMAND ${LLVM_CONFIG_EXE} --includedir
+      OUTPUT_VARIABLE LLVM_INCLUDE_DIRS_SPACES
+      OUTPUT_STRIP_TRAILING_WHITESPACE)
+  string(REPLACE " " ";" LLVM_INCLUDE_DIRS "${LLVM_INCLUDE_DIRS_SPACES}")
+
   if(NOT LLVM_LIBRARIES)
-    find_library(LLVM_LIBRARIES NAMES LLVM LLVM-14 LLVM-14.0 NAMES_PER_DIR)
+    find_library(LLVM_LIBRARIES
+      NAMES LLVM LLVM-14 LLVM-14.0 NAMES_PER_DIR
+      HINTS "${LLVM_CONFIG_DIR}/../lib" "${LLVM_CONFIG_DIR}/../lib64" "${LLVM_CONFIG_DIR}/../${CMAKE_LIBRARY_ARCHITECTURE}")
+
+    # TODO: Make this fallthrough work
   endif()
 
   link_directories("${CMAKE_PREFIX_PATH}/lib")
@@ -185,10 +179,13 @@ else()
 
   macro(FIND_AND_ADD_LLVM_LIB _libname_)
     string(TOUPPER ${_libname_} _prettylibname_)
-    find_library(LLVM_${_prettylibname_}_LIB NAMES ${_libname_} NAMES_PER_DIR PATHS ${LLVM_LIBDIRS})
+    find_library(LLVM_${_prettylibname_}_LIB
+      NAMES ${_libname_} NAMES_PER_DIR)
     set(LLVM_LIBRARIES ${LLVM_LIBRARIES} ${LLVM_${_prettylibname_}_LIB})
   endmacro(FIND_AND_ADD_LLVM_LIB)
 
+  set(LLVM_LINK_MODE "static")
+
   # This list can be re-generated with `llvm-config --libfiles` and then
   # reformatting using your favorite text editor. Note we do not execute
   # `llvm-config` here because we are cross compiling.
@@ -352,6 +349,9 @@ else()
   FIND_AND_ADD_LLVM_LIB(LLVMBinaryFormat)
   FIND_AND_ADD_LLVM_LIB(LLVMSupport)
   FIND_AND_ADD_LLVM_LIB(LLVMDemangle)
+
+  get_filename_component(LLVM_LIBDIRS "${LLVM_LLVMCORE_LIB}" DIRECTORY)
+  find_path(LLVM_INCLUDE_DIRS NAMES llvm/IR/IRBuilder.h)
 endif()
 
 include(FindPackageHandleStandardArgs)