[cmake] Explicitly mark libraries defined in lib/ as "Component Libraries"

Summary:
Most libraries are defined in the lib/ directory but there are also a
few libraries defined in tools/ e.g. libLLVM, libLTO.  I'm defining
"Component Libraries" as libraries defined in lib/ that may be included in
libLLVM.so.  Explicitly marking the libraries in lib/ as component
libraries allows us to remove some fragile checks that attempt to
differentiate between lib/ libraries and tools/ libraires:

1. In tools/llvm-shlib, because
llvm_map_components_to_libnames(LIB_NAMES "all") returned a list of
all libraries defined in the whole project, there was custom code
needed to filter out libraries defined in tools/, none of which should
be included in libLLVM.so.  This code assumed that any library
defined as static was from lib/ and everything else should be
excluded.

With this change, llvm_map_components_to_libnames(LIB_NAMES, "all")
only returns libraries that have been added to the LLVM_COMPONENT_LIBS
global cmake property, so this custom filtering logic can be removed.
Doing this also fixes the build with BUILD_SHARED_LIBS=ON
and LLVM_BUILD_LLVM_DYLIB=ON.

2. There was some code in llvm_add_library that assumed that
libraries defined in lib/ would not have LLVM_LINK_COMPONENTS or
ARG_LINK_COMPONENTS set.  This is only true because libraries
defined lib lib/ use LLVMBuild.txt and don't set these values.
This code has been fixed now to check if the library has been
explicitly marked as a component library, which should now make it
easier to remove LLVMBuild at some point in the future.

I have tested this patch on Windows, MacOS and Linux with release builds
and the following combinations of CMake options:

- "" (No options)
- -DLLVM_BUILD_LLVM_DYLIB=ON
- -DLLVM_LINK_LLVM_DYLIB=ON
- -DBUILD_SHARED_LIBS=ON
- -DBUILD_SHARED_LIBS=ON -DLLVM_BUILD_LLVM_DYLIB=ON
- -DBUILD_SHARED_LIBS=ON -DLLVM_LINK_LLVM_DYLIB=ON

Reviewers: beanz, smeenai, compnerd, phosek

Reviewed By: beanz

Subscribers: wuzish, jholewinski, arsenm, dschuff, jyknight, dylanmckay, sdardis, nemanjai, jvesely, nhaehnle, mgorny, mehdi_amini, sbc100, jgravelle-google, hiraditya, aheejin, fedor.sergeev, asb, rbar, johnrusso, simoncook, apazos, sabuasal, niosHD, jrtc27, MaskRay, zzheng, edward-jones, atanasyan, steven_wu, rogfer01, MartinMosbeck, brucehoult, the_o, dexonsmith, PkmX, jocewei, jsji, dang, Jim, lenary, s.egerton, pzheng, sameer.abuasal, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70179

2 files changed, 18 insertions, 4 deletions

diff --git a/llvm/cmake/modules/AddLLVM.cmake b/llvm/cmake/modules/AddLLVM.cmake
index 9ab04136026..518ea608d23 100644
--- a/llvm/cmake/modules/AddLLVM.cmake
+++ b/llvm/cmake/modules/AddLLVM.cmake
@@ -397,10 +397,14 @@ endfunction(set_windows_version_resource_properties)
 #     Suppress default RPATH settings in shared libraries.
 #   PLUGIN_TOOL
 #     The tool (i.e. cmake target) that this plugin will link against
+#   COMPONENT_LIB
+#      This is used to specify that this is a component library of
+#      LLVM which means that the source resides in llvm/lib/ and it is a
+#      candidate for inclusion into libLLVM.so.
 #   )
 function(llvm_add_library name)
   cmake_parse_arguments(ARG
-    "MODULE;SHARED;STATIC;OBJECT;DISABLE_LLVM_LINK_LLVM_DYLIB;SONAME;NO_INSTALL_RPATH"
+    "MODULE;SHARED;STATIC;OBJECT;DISABLE_LLVM_LINK_LLVM_DYLIB;SONAME;NO_INSTALL_RPATH;COMPONENT_LIB"
     "OUTPUT_NAME;PLUGIN_TOOL;ENTITLEMENTS;BUNDLE_PATH"
     "ADDITIONAL_HEADERS;DEPENDS;LINK_COMPONENTS;LINK_LIBS;OBJLIBS"
     ${ARGN})
@@ -486,6 +490,11 @@ function(llvm_add_library name)
     add_library(${name} STATIC ${ALL_FILES})
   endif()
 
+  if(ARG_COMPONENT_LIB)
+    set_target_properties(${name} PROPERTIES LLVM_COMPONENT TRUE)
+    set_property(GLOBAL APPEND PROPERTY LLVM_COMPONENT_LIBS ${name})
+  endif()
+
   if(NOT ARG_NO_INSTALL_RPATH)
     if(ARG_MODULE OR ARG_SHARED)
       llvm_setup_rpath(${name})
@@ -570,7 +579,7 @@ function(llvm_add_library name)
   if(ARG_MODULE AND LLVM_EXPORT_SYMBOLS_FOR_PLUGINS AND ARG_PLUGIN_TOOL AND (WIN32 OR CYGWIN))
     # On DLL platforms symbols are imported from the tool by linking against it.
     set(llvm_libs ${ARG_PLUGIN_TOOL})
-  elseif (DEFINED LLVM_LINK_COMPONENTS OR DEFINED ARG_LINK_COMPONENTS)
+  elseif (NOT ARG_COMPONENT_LIB)
     if (LLVM_LINK_LLVM_DYLIB AND NOT ARG_DISABLE_LLVM_LINK_LLVM_DYLIB)
       set(llvm_libs LLVM)
     else()
@@ -669,6 +678,10 @@ function(add_llvm_install_targets target)
   endif()
 endfunction()
 
+function(add_llvm_component_library name)
+  add_llvm_library(${name} COMPONENT_LIB ${ARGN})
+endfunction()
+
 macro(add_llvm_library name)
   cmake_parse_arguments(ARG
     "SHARED;BUILDTREE_ONLY;MODULE;INSTALL_WITH_TOOLCHAIN"
@@ -1027,7 +1040,7 @@ macro(add_llvm_target target_name)
   include_directories(BEFORE
     ${CMAKE_CURRENT_BINARY_DIR}
     ${CMAKE_CURRENT_SOURCE_DIR})
-  add_llvm_library(LLVM${target_name} ${ARGN})
+  add_llvm_component_library(LLVM${target_name} ${ARGN})
   set( CURRENT_LLVM_TARGET LLVM${target_name} )
 endmacro(add_llvm_target)
 
diff --git a/llvm/cmake/modules/LLVM-Config.cmake b/llvm/cmake/modules/LLVM-Config.cmake
index fd50ca6aae1..c3fa59e8335 100644
--- a/llvm/cmake/modules/LLVM-Config.cmake
+++ b/llvm/cmake/modules/LLVM-Config.cmake
@@ -267,7 +267,8 @@ function(llvm_map_components_to_libnames out_libs)
     elseif( c STREQUAL "engine" )
       # already processed
     elseif( c STREQUAL "all" )
-      list(APPEND expanded_components ${LLVM_AVAILABLE_LIBS})
+      get_property(all_components GLOBAL PROPERTY LLVM_COMPONENT_LIBS)
+      list(APPEND expanded_components ${all_components})
     else()
       # Canonize the component name:
       string(TOUPPER "${c}" capitalized)