Add support for Operation::moveBefore(Operation *).

PiperOrigin-RevId: 222252521

mlir/include/mlir/IR/Operation.h

@@ -120,6 +120,11 @@ public:
   /// Return true if there are no users of any results of this operation.
   bool use_empty() const;
 
+  /// Unlink this operation from its current block and insert it right before
+  /// `existingOp` which may be in the same or another block of the same
+  /// function.
+  void moveBefore(Operation *existingOp);
+
   // Attributes.  Operations may optionally carry a list of attributes that
   // associate constants to names.  Attributes may be dynamically added and
   // removed over the lifetime of an operation.

mlir/include/mlir/IR/Statements.h

@@ -56,6 +56,7 @@ public:
   using Statement::emitNote;
   using Statement::emitWarning;
   using Statement::getLoc;
+  using Statement::moveBefore;
   using Statement::print;
 
   /// Check if this statement is a return statement.

mlir/lib/IR/Operation.cpp

@@ -197,6 +197,13 @@ bool Operation::use_empty() const {
   return true;
 }
 
+void Operation::moveBefore(Operation *existingOp) {
+  if (auto *inst = llvm::dyn_cast<Instruction>(this))
+    return inst->moveBefore(llvm::cast<Instruction>(existingOp));
+  return llvm::cast<OperationStmt>(this)->moveBefore(
+      llvm::cast<OperationStmt>(existingOp));
+}
+
 ArrayRef<NamedAttribute> Operation::getAttrs() const {
   if (!attrs)
     return {};