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)

3 files changed, 25 insertions, 4 deletions

diff --git a/llvm/tools/bugpoint/CMakeLists.txt b/llvm/tools/bugpoint/CMakeLists.txt
index 0b5998e181e..b71ac919d91 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 6c31df3e173..fb12e29a36a 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 79613c836c5..d0abdf11130 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