Generalize the pass registration mechanism used by Polly to any third-party tool

There's quite a lot of references to Polly in the LLVM CMake codebase. However
the registration pattern used by Polly could be useful to other external
projects: thanks to that mechanism it would be possible to develop LLVM
extension without touching the LLVM code base.

This patch has two effects:

1. Remove all code specific to Polly in the llvm/clang codebase, replaicing it
   with a generic mechanism

2. Provide a generic mechanism to register compiler extensions.

A compiler extension is similar to a pass plugin, with the notable difference
that the compiler extension can be configured to be built dynamically (like
plugins) or statically (like regular passes).

As a result, people willing to add extra passes to clang/opt can do it using a
separate code repo, but still have their pass be linked in clang/opt as built-in
passes.

Differential Revision: https://reviews.llvm.org/D61446

2 files changed, 9 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
index 645ef0165a5..ed881f2ddf6 100644
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -75,6 +75,10 @@
 using namespace clang;
 using namespace llvm;
 
+#define HANDLE_EXTENSION(Ext)                                                  \
+  llvm::PassPluginLibraryInfo get##Ext##PluginInfo();
+#include "llvm/Support/Extension.def"
+
 namespace {
 
 // Default filename used for profile generation.
@@ -1076,6 +1080,9 @@ void EmitAssemblyHelper::EmitAssemblyWithNewPassManager(
           << PluginFN << toString(PassPlugin.takeError());
     }
   }
+#define HANDLE_EXTENSION(Ext)                                                  \
+  get##Ext##PluginInfo().RegisterPassBuilderCallbacks(PB);
+#include "llvm/Support/Extension.def"
 
   LoopAnalysisManager LAM(CodeGenOpts.DebugPassManager);
   FunctionAnalysisManager FAM(CodeGenOpts.DebugPassManager);
diff --git a/clang/lib/CodeGen/CMakeLists.txt b/clang/lib/CodeGen/CMakeLists.txt
index a3980637c59..d8b3c234a1e 100644
--- a/clang/lib/CodeGen/CMakeLists.txt
+++ b/clang/lib/CodeGen/CMakeLists.txt
@@ -96,6 +96,8 @@ add_clang_library(clangCodeGen
   TargetInfo.cpp
   VarBypassDetector.cpp
 
+  ENABLE_PLUGINS
+
   DEPENDS
   ${codegen_deps}