Add option to disable legacy pass manager to swift-llvm-opt

Author: aschwaighofer

tools/swift-llvm-opt/LLVMOpt.cpp

@@ -80,6 +80,11 @@ static llvm::codegen::RegisterCodeGenFlags CGF;
 static llvm::cl::list<const llvm::PassInfo *, bool, llvm::PassNameParser>
     PassList(llvm::cl::desc("Optimizations available:"));
 
+static llvm::cl::opt<bool>
+    UseLegacyPassManager("legacy-pass-manager",
+                         llvm::cl::desc("Use the legacy llvm pass manager"),
+                         llvm::cl::init(true));
+
 static llvm::cl::opt<bool>
     Optimized("O", llvm::cl::desc("Optimization level O. Similar to swift -O"));
 
@@ -309,6 +314,7 @@ int main(int argc, char **argv) {
   if (Optimized) {
     IRGenOptions Opts;
     Opts.OptMode = OptimizationMode::ForSpeed;
+    Opts.LegacyPassManager = UseLegacyPassManager;
 
     // Then perform the optimizations.
     performLLVMOptimizations(Opts, M.get(), TM.get());