[MLIR] Introduce a OpWithState class to act as a stream modifier for Operations (NFC) (llvm#151547)

On the model of OpWithFlags, this modifier allows to stream an operation
using a custom AsmPrinter.

Author: joker-eph

mlir/include/mlir/IR/Operation.h

@@ -1102,6 +1102,49 @@ inline raw_ostream &operator<<(raw_ostream &os, const Operation &op) {
   return os;
 }
 
+/// A wrapper class that allows for printing an operation with a set of flags,
+/// useful to act as a "stream modifier" to customize printing an operation
+/// with a stream using the operator<< overload, e.g.:
+///   llvm::dbgs() << OpWithFlags(op, OpPrintingFlags().skipRegions());
+class OpWithFlags {
+public:
+  OpWithFlags(Operation *op, OpPrintingFlags flags = {})
+      : op(op), theFlags(flags) {}
+  OpPrintingFlags &flags() { return theFlags; }
+  const OpPrintingFlags &flags() const { return theFlags; }
+
+private:
+  Operation *op;
+  OpPrintingFlags theFlags;
+  friend raw_ostream &operator<<(raw_ostream &os, const OpWithFlags &op);
+};
+
+inline raw_ostream &operator<<(raw_ostream &os,
+                               const OpWithFlags &opWithFlags) {
+  opWithFlags.op->print(os, opWithFlags.flags());
+  return os;
+}
+
+/// A wrapper class that allows for printing an operation with a custom
+/// AsmState, useful to act as a "stream modifier" to customize printing an
+/// operation with a stream using the operator<< overload, e.g.:
+///   llvm::dbgs() << OpWithState(op, OpPrintingFlags().skipRegions());
+class OpWithState {
+public:
+  OpWithState(Operation *op, AsmState &state) : op(op), theState(state) {}
+
+private:
+  Operation *op;
+  AsmState &theState;
+  friend raw_ostream &operator<<(raw_ostream &os, const OpWithState &op);
+};
+
+inline raw_ostream &operator<<(raw_ostream &os,
+                               const OpWithState &opWithState) {
+  opWithState.op->print(os, const_cast<OpWithState &>(opWithState).theState);
+  return os;
+}
+
 } // namespace mlir
 
 namespace llvm {

mlir/lib/Tools/mlir-opt/MlirOptMain.cpp

@@ -508,8 +508,7 @@ performActions(raw_ostream &os,
            << "bytecode version while not emitting bytecode";
   AsmState asmState(op.get(), OpPrintingFlags(), /*locationMap=*/nullptr,
                     &fallbackResourceMap);
-  op.get()->print(os, asmState);
-  os << '\n';
+  os << OpWithState(op.get(), asmState) << '\n';
   return success();
 }