InstructionSelect: Use GISelChangeObserver instead of MachineFunction::Delegate

llvm/include/llvm/CodeGen/GlobalISel/GISelChangeObserver.h

@@ -138,5 +138,19 @@ class RAIIMFObsDelInstaller {
   ~RAIIMFObsDelInstaller() = default;
 };
 
+/// A simple RAII based Observer installer.
+/// Use this in a scope to install the Observer to the MachineFunction and reset
+/// it at the end of the scope.
+class RAIITemporaryObserverInstaller {
+public:
+  RAIITemporaryObserverInstaller(GISelObserverWrapper &Observers,
+                                 GISelChangeObserver &TemporaryObserver);
+  ~RAIITemporaryObserverInstaller();
+
+private:
+  GISelObserverWrapper &Observers;
+  GISelChangeObserver &TemporaryObserver;
+};
+
 } // namespace llvm
 #endif

llvm/include/llvm/CodeGen/GlobalISel/InstructionSelector.h

@@ -16,6 +16,8 @@
 #include "llvm/CodeGen/GlobalISel/GIMatchTableExecutor.h"
 
 namespace llvm {
+class GISelObserverWrapper;
+
 class InstructionSelector : public GIMatchTableExecutor {
 public:
   virtual ~InstructionSelector();
@@ -36,6 +38,11 @@ class InstructionSelector : public GIMatchTableExecutor {
   const TargetPassConfig *TPC = nullptr;
 
   MachineOptimizationRemarkEmitter *MORE = nullptr;
+
+  /// Note: InstructionSelect does not track changed instructions.
+  /// changingInstr() and changedInstr() will never be called on these
+  /// observers.
+  GISelObserverWrapper *AllObservers = nullptr;
 };
 } // namespace llvm
 

llvm/lib/CodeGen/GlobalISel/GISelChangeObserver.cpp

@@ -46,3 +46,13 @@ RAIIMFObserverInstaller::RAIIMFObserverInstaller(MachineFunction &MF,
 }
 
 RAIIMFObserverInstaller::~RAIIMFObserverInstaller() { MF.setObserver(nullptr); }
+
+RAIITemporaryObserverInstaller::RAIITemporaryObserverInstaller(
+    GISelObserverWrapper &Observers, GISelChangeObserver &TemporaryObserver)
+    : Observers(Observers), TemporaryObserver(TemporaryObserver) {
+  Observers.addObserver(&TemporaryObserver);
+}
+
+RAIITemporaryObserverInstaller::~RAIITemporaryObserverInstaller() {
+  Observers.removeObserver(&TemporaryObserver);
+}

llvm/lib/CodeGen/GlobalISel/InstructionSelect.cpp

@@ -75,19 +75,25 @@ InstructionSelect::InstructionSelect(CodeGenOptLevel OL, char &PassID)
 /// a non-obvious limitation for selector implementers. Therefore, to allow
 /// deletion of arbitrary instructions, we detect this case and continue
 /// selection with the predecessor of the deleted instruction.
-class InstructionSelect::MIIteratorMaintainer
-    : public MachineFunction::Delegate {
+class InstructionSelect::MIIteratorMaintainer : public GISelChangeObserver {
 #ifndef NDEBUG
   SmallSetVector<const MachineInstr *, 32> CreatedInstrs;
 #endif
 public:
   MachineBasicBlock::reverse_iterator MII;
 
-  void MF_HandleInsertion(MachineInstr &MI) override {
+  void changingInstr(MachineInstr &MI) override {
+    llvm_unreachable("InstructionSelect does not track changed instructions!");
+  }
+  void changedInstr(MachineInstr &MI) override {
+    llvm_unreachable("InstructionSelect does not track changed instructions!");
+  }
+
+  void createdInstr(MachineInstr &MI) override {
     LLVM_DEBUG(dbgs() << "Creating:  " << MI; CreatedInstrs.insert(&MI));
   }
 
-  void MF_HandleRemoval(MachineInstr &MI) override {
+  void erasingInstr(MachineInstr &MI) override {
     LLVM_DEBUG(dbgs() << "Erasing:   " << MI; CreatedInstrs.remove(&MI));
     if (MII.getInstrIterator().getNodePtr() == &MI) {
       // If the iterator points to the MI that will be erased (i.e. the MI prior
@@ -190,8 +196,11 @@ bool InstructionSelect::selectMachineFunction(MachineFunction &MF) {
     // GISelChangeObserver, because we do not want notifications about changed
     // instructions. This prevents significant compile-time regressions from
     // e.g. constrainOperandRegClass().
+    GISelObserverWrapper AllObservers;
     MIIteratorMaintainer MIIMaintainer;
-    RAIIDelegateInstaller DelInstaller(MF, &MIIMaintainer);
+    AllObservers.addObserver(&MIIMaintainer);
+    RAIIDelegateInstaller DelInstaller(MF, &AllObservers);
+    ISel->AllObservers = &AllObservers;
 
     for (MachineBasicBlock *MBB : post_order(&MF)) {
       ISel->CurMBB = MBB;