Fixed crashes when no statement in scop in PlutoTransform

include/polymer/Support/OslScop.h

@@ -63,6 +63,9 @@ class OslScop {
   /// Get statement by index.
   mlir::LogicalResult getStatement(unsigned index, osl_statement **stmt);
 
+  /// Get the total number of statements
+  unsigned getNumStatements() const;
+
   /// Get extension by interface name
   osl_generic *getExtension(llvm::StringRef interface) const;
 

lib/Support/OslScop.cc

@@ -217,6 +217,10 @@ LogicalResult OslScop::getStatement(unsigned index, osl_statement **stmt) {
   return success();
 }
 
+unsigned OslScop::getNumStatements() const {
+  return osl_statement_number(scop->statement);
+}
+
 osl_generic_p OslScop::getExtension(llvm::StringRef tag) const {
   osl_generic_p ext = scop->extension;
   osl_interface_p interface = osl_interface_lookup(scop->registry, tag.data());

lib/Transforms/PlutoTransform.cc

@@ -75,7 +75,13 @@ struct PlutoTransform : public OpConversionPattern<mlir::FuncOp> {
           "Cannot emit a valid OpenScop representation from the given FuncOp.");
       return failure();
     }
-    // scop->print();
+
+    if (scop->getNumStatements() == 0) {
+      // TODO: Is there a good way to replace this pair?
+      rewriter.startRootUpdate(funcOp);
+      rewriter.finalizeRootUpdate(funcOp);
+      return success();
+    }
 
     // Should use isldep, candl cannot work well for this case.
     // TODO: should discover why.

test/polymer-opt/PlutoTransform/empty.mlir

@@ -0,0 +1,9 @@
+// RUN: polymer-opt %s -pluto-opt | FileCheck %s
+
+func @empty() {
+  return 
+}
+
+// CHECK:      func @empty() {
+// CHECK-NEXT:   return
+// CHECK-NEXT: }