[cmake] rework LLVM_LINK_LLVM_DYLIB option handling

Summary:
This diff attempts to address the concerns raised in
http://reviews.llvm.org/D12488.

We introduce a new USE_SHARED option to llvm_config,
which, if set, causes the target to be linked against
libLLVM.

add_llvm_utility now uniformly disables linking against
libLLVM. These utilities are not intended for distribution,
and this keeps the option handling more centralised.

llvm-shlib is now processes before any other "tools"
subdirectories, ensuring the libLLVM target is defined
before its dependents.

One main difference from what was requested: llvm_config
does not prune LLVM_DYLIB_COMPONENTS from the components
passed into explicit_llvm_config. This is because the "all"
component does something special, adding additional
libraries (namely libLTO). Adding the component libraries
after libLLVM should not be a problem, as symbols will be
resolved in libLLVM first.

Finally, I'm not really happy with the
DISABLE_LLVM_LINK_LLVM option, but I'm not sure of a
better way to get the following:
 - link all tools and shared libraries to libLLVM if
   LLVM_LINK_LLVM_DYLIB is set
 - some way of explicitly *not* doing so for utilities
   and libLLVM itself
Suggestions for improvement here are particularly welcome.

Reviewers: beanz

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D12590

llvm-svn: 246918

3 files changed, 24 insertions, 14 deletions

diff --git a/llvm/cmake/modules/AddLLVM.cmake b/llvm/cmake/modules/AddLLVM.cmake
index f53b89d32ab..0f3b660b95f 100644
--- a/llvm/cmake/modules/AddLLVM.cmake
+++ b/llvm/cmake/modules/AddLLVM.cmake
@@ -610,13 +610,13 @@ macro(add_llvm_executable name)
     add_llvm_symbol_exports( ${name} ${LLVM_EXPORTED_SYMBOL_FILE} )
   endif(LLVM_EXPORTED_SYMBOL_FILE)
 
-  set(EXCLUDE_FROM_ALL OFF)
-  set_output_directory(${name} ${LLVM_RUNTIME_OUTPUT_INTDIR} ${LLVM_LIBRARY_OUTPUT_INTDIR})
   if (LLVM_LINK_LLVM_DYLIB AND NOT ARG_DISABLE_LLVM_LINK_LLVM_DYLIB)
-    target_link_libraries(${name} LLVM)
-  else()
-    llvm_config( ${name} ${LLVM_LINK_COMPONENTS} )
+    set(USE_SHARED USE_SHARED)
   endif()
+
+  set(EXCLUDE_FROM_ALL OFF)
+  set_output_directory(${name} ${LLVM_RUNTIME_OUTPUT_INTDIR} ${LLVM_LIBRARY_OUTPUT_INTDIR})
+  llvm_config( ${name} ${USE_SHARED} ${LLVM_LINK_COMPONENTS} )
   if( LLVM_COMMON_DEPENDS )
     add_dependencies( ${name} ${LLVM_COMMON_DEPENDS} )
   endif( LLVM_COMMON_DEPENDS )
@@ -677,7 +677,7 @@ endmacro(add_llvm_example name)
 
 
 macro(add_llvm_utility name)
-  add_llvm_executable(${name} ${ARGN})
+  add_llvm_executable(${name} DISABLE_LLVM_LINK_LLVM_DYLIB ${ARGN})
   set_target_properties(${name} PROPERTIES FOLDER "Utils")
   if( LLVM_INSTALL_UTILS )
     install (TARGETS ${name}
diff --git a/llvm/cmake/modules/LLVM-Config.cmake b/llvm/cmake/modules/LLVM-Config.cmake
index 22ac7145191..aa68b400760 100644
--- a/llvm/cmake/modules/LLVM-Config.cmake
+++ b/llvm/cmake/modules/LLVM-Config.cmake
@@ -31,7 +31,23 @@ endfunction(is_llvm_target_library)
 
 
 macro(llvm_config executable)
-  explicit_llvm_config(${executable} ${ARGN})
+  cmake_parse_arguments(ARG "USE_SHARED" "" "" ${ARGN})
+  set(link_components ${ARG_UNPARSED_ARGUMENTS})
+
+  if(USE_SHARED)
+    # If USE_SHARED is specified, then we link against libLLVM,
+    # but also against the component libraries below. This is
+    # done in case libLLVM does not contain all of the components
+    # the target requires.
+    #
+    # TODO strip LLVM_DYLIB_COMPONENTS out of link_components.
+    # To do this, we need special handling for "all", since that
+    # may imply linking to libraries that are not included in
+    # libLLVM.
+    target_link_libraries(${executable} LLVM)
+  endif()
+
+  explicit_llvm_config(${executable} ${link_components})
 endmacro(llvm_config)
 
 
diff --git a/llvm/cmake/modules/TableGen.cmake b/llvm/cmake/modules/TableGen.cmake
index 98646bc16df..452a728db4f 100644
--- a/llvm/cmake/modules/TableGen.cmake
+++ b/llvm/cmake/modules/TableGen.cmake
@@ -79,13 +79,7 @@ macro(add_tablegen target project)
     set(LLVM_ENABLE_OBJLIB ON)
   endif()
 
-  add_llvm_utility(
-    ${target} ${ARGN}
-    # libLLVM does not include the TableGen
-    # components, so we cannot link any tblgen
-    # utilities against it.
-    DISABLE_LLVM_LINK_LLVM_DYLIB)
-
+  add_llvm_utility(${target} ${ARGN})
   set(LLVM_LINK_COMPONENTS ${${target}_OLD_LLVM_LINK_COMPONENTS})
 
   set(${project}_TABLEGEN "${target}" CACHE