[opt] Error if -debug-pass is specified alongside the new PM

[aeubanks]

add flag to use legacy PM

[ychen]

Sounds good. Does this happen for Clang too? With clang -Xclang -mllvm -Xclang -debug-pass=Structure -fexperimental-new-pass-manager, it still prints the legacy PM passes?

[aeubanks]

I can do that for clang in a separate change

[ychen]

LGTM

llvm/include/llvm/IR/LegacyPassManager.h

 
 namespace llvm {
 
 class Pass;
 class Module;
 
 namespace legacy {
 
+// Whether or not -debug-pass has been specified. For use to check if it's
+// specified alongside the new PM.
+bool debugPassSpecified();
+
 class PassManagerImpl;
 class FunctionPassManagerImpl;
 
 /// PassManagerBase - An abstract interface to allow code to add passes to
 /// a pass manager without having to hard-code what kind of pass manager
 /// it is.
 class PassManagerBase {
 public:

llvm/lib/IR/LegacyPassManager.cpp

void PassManagerPrettyStackEntry::print(raw_ostream &OS) const {
 
   OS << " '";
   V->printAsOperand(OS, /*PrintType=*/false, M);
   OS << "'\n";
 }
 
 namespace llvm {
 namespace legacy {
+bool debugPassSpecified() { return PassDebugging != Disabled; }
+
 //===----------------------------------------------------------------------===//
 // FunctionPassManagerImpl
 //
 /// FunctionPassManagerImpl manages FPPassManagers
 class FunctionPassManagerImpl : public Pass,
                                 public PMDataManager,
                                 public PMTopLevelManager {
   virtual void anchor();

llvm/test/Other/debug-pass-npm.ll

+; RUN: opt -enable-new-pm=0 -O1 %s -debug-pass=Structure
+; RUN: not opt -enable-new-pm=1 -O1 %s -debug-pass=Structure 2>&1 | FileCheck %s
+
+; CHECK: does not work

llvm/tools/opt/opt.cpp

if ((EnableNewPassManager && !shouldForceLegacyPM()) ||
       PassPipeline.getNumOccurrences() > 0) {
     if (AnalyzeOnly) {
       errs() << "Cannot specify -analyze under new pass manager, either "
                 "specify '-enable-new-pm=0', or use the corresponding new pass "
                 "manager pass, e.g. '-passes=print<scalar-evolution>'. For a "
                 "full list of passes, see the '--print-passes' flag.\n";
       return 1;
     }
+    if (legacy::debugPassSpecified()) {
+      errs()
+          << "-debug-pass does not work with the new PM, either use "
+             "-debug-pass-manager, or use the legacy PM (-enable-new-pm=0)\n";
+      return 1;
+    }
     if (PassPipeline.getNumOccurrences() > 0 && PassList.size() > 0) {
       errs()
           << "Cannot specify passes via both -foo-pass and --passes=foo-pass\n";
       return 1;
     }
     SmallVector<StringRef, 4> Passes;
     if (OptLevelO0)
       Passes.push_back("default<O0>");