[IRGen] Lift call to performLLVM out of IRGenRequest

Remove the side-effecting call from IRGenRequest,
instead requiring callers to handle the optimization
and emission of the LLVM module.

Author: hamishknight

include/swift/Subsystems.h

@@ -204,9 +204,8 @@ namespace swift {
              std::string>
   getIRTargetOptions(const IRGenOptions &Opts, ASTContext &Ctx);
 
-  /// Turn the given Swift module into either LLVM IR or native code
-  /// and return the generated LLVM IR module.
-  /// If you set an outModuleHash, then you need to call performLLVM.
+  /// Turn the given Swift module into LLVM IR and return the generated module.
+  /// To compile and output the generated code, call \c performLLVM.
   GeneratedModule
   performIRGeneration(ModuleDecl *M, const IRGenOptions &Opts,
                       const TBDGenOptions &TBDOpts,
@@ -215,9 +214,8 @@ namespace swift {
                       ArrayRef<std::string> parallelOutputFilenames,
                       llvm::GlobalVariable **outModuleHash = nullptr);
 
-  /// Turn the given Swift file into either LLVM IR or native code
-  /// and return the generated LLVM IR module.
-  /// If you set an outModuleHash, then you need to call performLLVM.
+  /// Turn the given Swift file into LLVM IR and return the generated module.
+  /// To compile and output the generated code, call \c performLLVM.
   GeneratedModule
   performIRGeneration(FileUnit *file, const IRGenOptions &Opts, 
                       const TBDGenOptions &TBDOpts,

lib/IRGen/IRGen.cpp

@@ -996,26 +996,18 @@ GeneratedModule IRGenRequest::evaluate(Evaluator &evaluator,
   if (Ctx.hadError()) return GeneratedModule::null();
 
   // Free the memory occupied by the SILModule.
-  // Execute this task in parallel to the LLVM compilation.
+  // Execute this task in parallel to the embedding of bitcode.
   auto SILModuleRelease = [&SILMod]() { SILMod.reset(nullptr); };
   auto Thread = std::thread(SILModuleRelease);
   // Wait for the thread to terminate.
   SWIFT_DEFER { Thread.join(); };
 
   embedBitcode(IGM.getModule(), Opts);
 
+  // TODO: Turn the module hash into an actual output.
   if (auto **outModuleHash = desc.outModuleHash) {
     *outModuleHash = IGM.ModuleHash;
-  } else {
-    FrontendStatsTracer tracer(Ctx.Stats, "LLVM pipeline");
-
-    // Since no out module hash was set, we need to performLLVM.
-    if (performLLVM(Opts, IGM.Context.Diags, nullptr, IGM.ModuleHash,
-                    IGM.getModule(), IGM.TargetMachine.get(),
-                    IGM.OutputFilename, IGM.Context.Stats))
-      return GeneratedModule::null();
   }
-
   return std::move(IGM).intoGeneratedModule();
 }
 

lib/Immediate/Immediate.cpp

@@ -196,6 +196,7 @@ int swift::RunImmediately(CompilerInstance &CI,
                           const IRGenOptions &IRGenOpts,
                           const SILOptions &SILOpts,
                           std::unique_ptr<SILModule> &&SM) {
+  // TODO: Use OptimizedIRRequest for this.
   ASTContext &Context = CI.getASTContext();
 
   // IRGen the main module.
@@ -211,6 +212,13 @@ int swift::RunImmediately(CompilerInstance &CI,
 
   assert(GenModule && "Emitted no diagnostics but IR generation failed?");
 
+  performLLVM(IRGenOpts, Context.Diags, /*diagMutex*/ nullptr, /*hash*/ nullptr,
+              GenModule.getModule(), GenModule.getTargetMachine(),
+              PSPs.OutputFilename, Context.Stats);
+
+  if (Context.hadError())
+    return -1;
+
   // Load libSwiftCore to setup process arguments.
   //
   // This must be done here, before any library loading has been done, to avoid

tools/sil-llvm-gen/SILLLVMGen.cpp

@@ -201,5 +201,11 @@ int main(int argc, char **argv) {
                                  std::move(SILMod),
                                  CI.getMainModule()->getName().str(), PSPs,
                                  ArrayRef<std::string>());
+  if (!Mod)
+    return 1;
+
+  performLLVM(Opts, CI.getDiags(), /*diagMutex*/ nullptr, /*hash*/ nullptr,
+              Mod.getModule(), Mod.getTargetMachine(), OutputFilename,
+              CI.getASTContext().Stats);
   return CI.getASTContext().hadError();
 }