Update compiler extension integration into the build system

The approach here is to create a new (empty) component, `Extensions', where all
statically compiled extensions dynamically register their dependencies. That way
we're more natively compatible with LLVMBuild and llvm-config.

Fixes: https://bugs.llvm.org/show_bug.cgi?id=44870

Differential Revision: https://reviews.llvm.org/D78192

(cherry picked from commit 8f766e382b77eef3102798b49e087d1e4804b984)

12 files changed, 113 insertions, 22 deletions

diff --git a/clang/lib/CodeGen/CMakeLists.txt b/clang/lib/CodeGen/CMakeLists.txt
index d8b3c234a1ef..c300c1b021f3 100644
--- a/clang/lib/CodeGen/CMakeLists.txt
+++ b/clang/lib/CodeGen/CMakeLists.txt
@@ -5,6 +5,7 @@ set(LLVM_LINK_COMPONENTS
   Core
   Coroutines
   Coverage
+  Extensions
   FrontendOpenMP
   IPO
   IRReader
@@ -96,8 +97,6 @@ add_clang_library(clangCodeGen
   TargetInfo.cpp
   VarBypassDetector.cpp
 
-  ENABLE_PLUGINS
-
   DEPENDS
   ${codegen_deps}
 
diff --git a/llvm/cmake/modules/AddLLVM.cmake b/llvm/cmake/modules/AddLLVM.cmake
index a8b3628fd311..37387e0fc542 100644
--- a/llvm/cmake/modules/AddLLVM.cmake
+++ b/llvm/cmake/modules/AddLLVM.cmake
@@ -404,7 +404,7 @@ endfunction(set_windows_version_resource_properties)
 #   )
 function(llvm_add_library name)
   cmake_parse_arguments(ARG
-    "MODULE;SHARED;STATIC;OBJECT;DISABLE_LLVM_LINK_LLVM_DYLIB;SONAME;NO_INSTALL_RPATH;COMPONENT_LIB;ENABLE_PLUGINS"
+    "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})
@@ -418,9 +418,6 @@ function(llvm_add_library name)
   else()
     llvm_process_sources(ALL_FILES ${ARG_UNPARSED_ARGUMENTS} ${ARG_ADDITIONAL_HEADERS})
   endif()
-  if(ARG_ENABLE_PLUGINS)
-    set_property(GLOBAL APPEND PROPERTY LLVM_PLUGIN_TARGETS ${name})
-  endif()
 
   if(ARG_MODULE)
     if(ARG_SHARED OR ARG_STATIC)
@@ -753,7 +750,7 @@ endmacro(add_llvm_library name)
 
 macro(add_llvm_executable name)
   cmake_parse_arguments(ARG
-    "DISABLE_LLVM_LINK_LLVM_DYLIB;IGNORE_EXTERNALIZE_DEBUGINFO;NO_INSTALL_RPATH;SUPPORT_PLUGINS;ENABLE_PLUGINS"
+    "DISABLE_LLVM_LINK_LLVM_DYLIB;IGNORE_EXTERNALIZE_DEBUGINFO;NO_INSTALL_RPATH;SUPPORT_PLUGINS"
     "ENTITLEMENTS;BUNDLE_PATH"
     "DEPENDS"
     ${ARGN})
@@ -840,9 +837,6 @@ macro(add_llvm_executable name)
     # API for all shared libaries loaded by this executable.
     target_link_libraries(${name} PRIVATE ${LLVM_PTHREAD_LIB})
   endif()
-  if(ARG_ENABLE_PLUGINS)
-    set_property(GLOBAL APPEND PROPERTY LLVM_PLUGIN_TARGETS ${name})
-  endif()
 
   llvm_codesign(${name} ENTITLEMENTS ${ARG_ENTITLEMENTS} BUNDLE_PATH ${ARG_BUNDLE_PATH})
 endmacro(add_llvm_executable name)
@@ -915,18 +909,18 @@ function(process_llvm_pass_plugins)
       include(LLVMConfigExtensions)
   endif()
 
-  # Add static plugins to each plugin target.
+  # Add static plugins to the Extension component
   foreach(llvm_extension ${LLVM_STATIC_EXTENSIONS})
-    get_property(llvm_plugin_targets GLOBAL PROPERTY LLVM_PLUGIN_TARGETS)
-    foreach(llvm_plugin_target ${llvm_plugin_targets})
-      set_property(TARGET ${llvm_plugin_target} APPEND PROPERTY LINK_LIBRARIES ${llvm_extension})
-      set_property(TARGET ${llvm_plugin_target} APPEND PROPERTY INTERFACE_LINK_LIBRARIES ${llvm_extension})
-    endforeach()
+      set_property(TARGET LLVMExtensions APPEND PROPERTY LINK_LIBRARIES ${llvm_extension})
+      set_property(TARGET LLVMExtensions APPEND PROPERTY INTERFACE_LINK_LIBRARIES ${llvm_extension})
   endforeach()
 
-  # Eventually generate the extension header, and store config to a cmake file
+  # Eventually generate the extension headers, and store config to a cmake file
   # for usage in third-party configuration.
   if(ARG_GEN_CONFIG)
+
+      ## Part 1: Extension header to be included whenever we need extension
+      #  processing.
       set(LLVM_INSTALL_PACKAGE_DIR lib${LLVM_LIBDIR_SUFFIX}/cmake/llvm)
       set(llvm_cmake_builddir "${LLVM_BINARY_DIR}/${LLVM_INSTALL_PACKAGE_DIR}")
       file(WRITE
@@ -949,6 +943,57 @@ function(process_llvm_pass_plugins)
           "${ExtensionDef}.tmp"
           "${ExtensionDef}")
       file(REMOVE "${ExtensionDef}.tmp")
+
+      ## Part 2: Extension header that captures each extension dependency, to be
+      #  used by llvm-config.
+      set(ExtensionDeps "${LLVM_BINARY_DIR}/tools/llvm-config/ExtensionDependencies.inc")
+
+      # Max needed to correctly size the required library array.
+      set(llvm_plugin_max_deps_length 0)
+      foreach(llvm_extension ${LLVM_STATIC_EXTENSIONS})
+        get_property(llvm_plugin_deps TARGET ${llvm_extension} PROPERTY LINK_LIBRARIES)
+        list(LENGTH llvm_plugin_deps llvm_plugin_deps_length)
+        if(llvm_plugin_deps_length GREATER llvm_plugin_max_deps_length)
+            set(llvm_plugin_max_deps_length ${llvm_plugin_deps_length})
+        endif()
+      endforeach()
+
+      list(LENGTH LLVM_STATIC_EXTENSIONS llvm_static_extension_count)
+      file(WRITE
+          "${ExtensionDeps}.tmp"
+          "#include <array>\n\
+           struct ExtensionDescriptor {\n\
+              const char* Name;\n\
+              const char* const RequiredLibraries[1 + 1 + ${llvm_plugin_max_deps_length}];\n\
+           };\n\
+           std::array<ExtensionDescriptor, ${llvm_static_extension_count}>  AvailableExtensions{\n")
+
+      foreach(llvm_extension ${LLVM_STATIC_EXTENSIONS})
+        get_property(llvm_plugin_deps TARGET ${llvm_extension} PROPERTY LINK_LIBRARIES)
+
+        file(APPEND "${ExtensionDeps}.tmp" "{\"${llvm_extension}\", {")
+        foreach(llvm_plugin_dep ${llvm_plugin_deps})
+            # Turn library dependency back to component name, if possible.
+            # That way llvm-config can avoid redundant dependencies.
+            STRING(REGEX REPLACE "^-l" ""  plugin_dep_name ${llvm_plugin_dep})
+            STRING(REGEX MATCH "^LLVM" is_llvm_library ${plugin_dep_name})
+            if(is_llvm_library)
+                STRING(REGEX REPLACE "^LLVM" ""  plugin_dep_name ${plugin_dep_name})
+                STRING(TOLOWER ${plugin_dep_name} plugin_dep_name)
+            endif()
+            file(APPEND "${ExtensionDeps}.tmp" "\"${plugin_dep_name}\", ")
+        endforeach()
+
+        # Self + mandatory trailing null, because the number of RequiredLibraries differs between extensions.
+        file(APPEND "${ExtensionDeps}.tmp" \"${llvm_extension}\", "nullptr}},\n")
+      endforeach()
+      file(APPEND "${ExtensionDeps}.tmp" "};\n")
+
+      # only replace if there's an actual change
+      execute_process(COMMAND ${CMAKE_COMMAND} -E copy_if_different
+          "${ExtensionDeps}.tmp"
+          "${ExtensionDeps}")
+      file(REMOVE "${ExtensionDeps}.tmp")
   endif()
 endfunction()
 
diff --git a/llvm/lib/CMakeLists.txt b/llvm/lib/CMakeLists.txt
index 8f8d417124c8..abe3ec59aec1 100644
--- a/llvm/lib/CMakeLists.txt
+++ b/llvm/lib/CMakeLists.txt
@@ -9,6 +9,7 @@ add_subdirectory(BinaryFormat)
 add_subdirectory(Bitcode)
 add_subdirectory(Bitstream)
 add_subdirectory(DWARFLinker)
+add_subdirectory(Extensions)
 add_subdirectory(Frontend)
 add_subdirectory(Transforms)
 add_subdirectory(Linker)
diff --git a/llvm/lib/Extensions/CMakeLists.txt b/llvm/lib/Extensions/CMakeLists.txt
new file mode 100644
index 000000000000..701e9c4c0baf
--- /dev/null
+++ b/llvm/lib/Extensions/CMakeLists.txt
@@ -0,0 +1,3 @@
+add_llvm_component_library(LLVMExtensions
+    Extensions.cpp
+)
diff --git a/llvm/lib/Extensions/Extensions.cpp b/llvm/lib/Extensions/Extensions.cpp
new file mode 100644
index 000000000000..e69de29bb2d1
--- /dev/null
+++ b/llvm/lib/Extensions/Extensions.cpp
diff --git a/llvm/lib/Extensions/LLVMBuild.txt b/llvm/lib/Extensions/LLVMBuild.txt
new file mode 100644
index 000000000000..2005830a4dd7
--- /dev/null
+++ b/llvm/lib/Extensions/LLVMBuild.txt
@@ -0,0 +1,21 @@
+;===- ./lib/Extensions/LLVMBuild.txt -------------------------------*- Conf -*--===;
+;
+; Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+; See https://llvm.org/LICENSE.txt for license information.
+; SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+;
+;===------------------------------------------------------------------------===;
+;
+; This is an LLVMBuild description file for the components in this subdirectory.
+;
+; For more information on the LLVMBuild system, please see:
+;
+;   http://llvm.org/docs/LLVMBuild.html
+;
+;===------------------------------------------------------------------------===;
+
+[component_0]
+type = Library
+name = Extensions
+parent = Libraries
+required_libraries =
diff --git a/llvm/lib/LLVMBuild.txt b/llvm/lib/LLVMBuild.txt
index 1ae59791cd6c..824abd36fc99 100644
--- a/llvm/lib/LLVMBuild.txt
+++ b/llvm/lib/LLVMBuild.txt
@@ -25,6 +25,7 @@ subdirectories =
  Demangle
  DWARFLinker
  ExecutionEngine
+ Extensions
  Frontend
  FuzzMutate
  LineEditor
diff --git a/llvm/lib/LTO/CMakeLists.txt b/llvm/lib/LTO/CMakeLists.txt
index ecafb96856f4..55f1a5a85fa5 100644
--- a/llvm/lib/LTO/CMakeLists.txt
+++ b/llvm/lib/LTO/CMakeLists.txt
@@ -10,7 +10,6 @@ add_llvm_component_library(LLVMLTO
 
   ADDITIONAL_HEADER_DIRS
   ${LLVM_MAIN_INCLUDE_DIR}/llvm/LTO
-
   DEPENDS
   intrinsics_gen
   llvm_vcsrevision_h
diff --git a/llvm/lib/LTO/LLVMBuild.txt b/llvm/lib/LTO/LLVMBuild.txt
index 1afbe1ff2d85..68bbeb6957db 100644
--- a/llvm/lib/LTO/LLVMBuild.txt
+++ b/llvm/lib/LTO/LLVMBuild.txt
@@ -25,6 +25,7 @@ required_libraries =
  BitWriter
  CodeGen
  Core
+ Extensions
  IPO
  InstCombine
  Linker
diff --git a/llvm/tools/bugpoint/CMakeLists.txt b/llvm/tools/bugpoint/CMakeLists.txt
index 0b5998e181eb..b71ac919d911 100644
--- a/llvm/tools/bugpoint/CMakeLists.txt
+++ b/llvm/tools/bugpoint/CMakeLists.txt
@@ -6,6 +6,7 @@ set(LLVM_LINK_COMPONENTS
   Analysis
   BitWriter
   CodeGen
+  Extensions
   Core
   IPO
   IRReader
@@ -32,8 +33,6 @@ add_llvm_tool(bugpoint
   ToolRunner.cpp
   bugpoint.cpp
 
-  ENABLE_PLUGINS
-
   DEPENDS
   intrinsics_gen
   SUPPORT_PLUGINS
diff --git a/llvm/tools/llvm-config/llvm-config.cpp b/llvm/tools/llvm-config/llvm-config.cpp
index 6c31df3e173b..fb12e29a36a8 100644
--- a/llvm/tools/llvm-config/llvm-config.cpp
+++ b/llvm/tools/llvm-config/llvm-config.cpp
@@ -46,6 +46,10 @@ using namespace llvm;
 // create entries for pseudo groups like x86 or all-targets.
 #include "LibraryDependencies.inc"
 
+// Built-in extensions also register their dependencies, but in a separate file,
+// later in the process.
+#include "ExtensionDependencies.inc"
+
 // LinkMode determines what libraries and flags are returned by llvm-config.
 enum LinkMode {
   // LinkModeAuto will link with the default link mode for the installation,
@@ -110,6 +114,25 @@ static void VisitComponent(const std::string &Name,
                    GetComponentLibraryPath, Missing, DirSep);
   }
 
+  // Special handling for the special 'extensions' component. Its content is
+  // not populated by llvm-build, but later in the process and loaded from
+  // ExtensionDependencies.inc.
+  if (Name == "extensions") {
+    for (auto const &AvailableExtension : AvailableExtensions) {
+      for (const char *const *Iter = &AvailableExtension.RequiredLibraries[0];
+           *Iter; ++Iter) {
+        AvailableComponent *AC = ComponentMap.lookup(*Iter);
+        if (!AC) {
+          RequiredLibs.push_back(*Iter);
+        } else {
+          VisitComponent(*Iter, ComponentMap, VisitedComponents, RequiredLibs,
+                         IncludeNonInstalled, GetComponentNames,
+                         GetComponentLibraryPath, Missing, DirSep);
+        }
+      }
+    }
+  }
+
   if (GetComponentNames) {
     RequiredLibs.push_back(Name);
     return;
diff --git a/llvm/tools/opt/CMakeLists.txt b/llvm/tools/opt/CMakeLists.txt
index 79613c836c53..d0abdf111302 100644
--- a/llvm/tools/opt/CMakeLists.txt
+++ b/llvm/tools/opt/CMakeLists.txt
@@ -9,6 +9,7 @@ set(LLVM_LINK_COMPONENTS
   CodeGen
   Core
   Coroutines
+  Extensions
   IPO
   IRReader
   InstCombine
@@ -33,8 +34,6 @@ add_llvm_tool(opt
   PrintSCC.cpp
   opt.cpp
 
-  ENABLE_PLUGINS
-
   DEPENDS
   intrinsics_gen
   SUPPORT_PLUGINS