Add plugin support (#15169)

Add plugin support and pass LLVM arguments after plugins have been loaded.

include/cling/Interpreter/InvocationOptions.h

@@ -74,6 +74,9 @@ namespace cling {
     ///\brief The remaining arguments to pass to clang.
     ///
     std::vector<const char*> Remaining;
+
+    /// A list of arguments to forward to LLVM's option processing.
+    std::vector<std::string> LLVMArgs;
   };
 
   class InvocationOptions {

lib/Interpreter/BackendPasses.cpp

@@ -20,6 +20,7 @@
 #include "llvm/IR/PassManager.h"
 #include "llvm/IR/Verifier.h"
 #include "llvm/Passes/PassBuilder.h"
+#include "llvm/Passes/PassPlugin.h"
 #include "llvm/Passes/StandardInstrumentations.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Transforms/IPO.h"
@@ -399,6 +400,14 @@ void BackendPasses::CreatePasses(int OptLevel, llvm::ModulePassManager& MPM,
   std::optional<PGOOptions> PGOOpt;
   PassBuilder PB(&m_TM, PTO, PGOOpt, &PIC);
 
+  // Attempt to load pass plugins and register their callbacks with PB.
+  for (auto& PluginFN : m_CGOpts.PassPlugins) {
+    auto PassPlugin = PassPlugin::Load(PluginFN);
+    if (PassPlugin) {
+      PassPlugin->registerPassBuilderCallbacks(PB);
+    }
+  }
+
   if (!m_CGOpts.DisableLLVMPasses) {
     // Use the default pass pipeline. We also have to map our optimization
     // levels into one of the distinct levels used to configure the pipeline.

lib/Interpreter/Interpreter.cpp

@@ -220,6 +220,21 @@ namespace cling {
     if (!m_IncrParser->isValid(false))
       return;
 
+    // Load any requested plugins.
+    getCI()->LoadRequestedPlugins();
+
+    // Honor set of `-mllvm` options. This should happen AFTER plugins have been
+    // loaded!
+    if (!m_Opts.CompilerOpts.LLVMArgs.empty()) {
+      unsigned NumArgs = m_Opts.CompilerOpts.LLVMArgs.size();
+      auto Args = std::make_unique<const char*[]>(NumArgs + 2);
+      Args[0] = "cling (LLVM option parsing)";
+      for (unsigned i = 0; i != NumArgs; ++i)
+        Args[i + 1] = m_Opts.CompilerOpts.LLVMArgs[i].c_str();
+      Args[NumArgs + 1] = nullptr;
+      llvm::cl::ParseCommandLineOptions(NumArgs + 1, Args.get());
+    }
+
     // Initialize the opt level to what CodeGenOpts says.
     if (m_OptLevel == -1)
       setDefaultOptLevel(getCI()->getCodeGenOpts().OptimizationLevel);

lib/Interpreter/InvocationOptions.cpp

@@ -159,9 +159,6 @@ void CompilerOptions::Parse(int argc, const char* const argv[],
                     MissingArgCount, 0,
                     options::NoDriverOption | options::CLOption | options::DXCOption));
 
-  std::vector<const char*> LLVMArgs;
-  LLVMArgs.push_back("cling (LLVM option parsing)");
-
   for (const Arg* arg : Args) {
     switch (arg->getOption().getID()) {
       // case options::OPT_d_Flag:
@@ -202,12 +199,6 @@ void CompilerOptions::Parse(int argc, const char* const argv[],
         break;
     }
   }
-
-  // Check that there were LLVM arguments, other than the first dummy entry.
-  if (LLVMArgs.size() > 1) {
-    LLVMArgs.push_back(nullptr);
-    llvm::cl::ParseCommandLineOptions(LLVMArgs.size() - 1, LLVMArgs.data());
-  }
 }
 
 bool CompilerOptions::DefaultLanguage(const LangOptions* LangOpts) const {