[mlir] Fix printing when linalg.map has no inputs.

mlir/lib/Dialect/Linalg/IR/LinalgOps.cpp

if (!inputs.empty())
     p << " ins(" << inputs << " : " << inputs.getTypes() << ")";
   if (!outputs.empty())
     p << " outs(" << outputs << " : " << outputs.getTypes() << ")";
 }
 
 static void printCommonStructuredOpPartsWithNewLine(OpAsmPrinter &p,
                                                     ValueRange inputs,
                                                     ValueRange outputs) {
+  if (!inputs.empty()) {
     p.printNewline();
-  if (!inputs.empty())
     p << "ins(" << inputs << " : " << inputs.getTypes() << ")";
+  }
+  if (!outputs.empty()) {
     p.printNewline();
-  if (!outputs.empty())
     p << "outs(" << outputs << " : " << outputs.getTypes() << ")";
   }
+}
 //===----------------------------------------------------------------------===//
 // Specific parsing and printing for named structured ops created by ods-gen.
 //===----------------------------------------------------------------------===//
 
 static ParseResult parseNamedStructuredOpRegion(
     OpAsmParser &parser, Region &region, unsigned numRegionArgs,
     TypeRange inputTypes, TypeRange outputTypes, ArrayRef<NamedAttribute> attrs,
     RegionBuilderFn regionBuilder) {

mlir/test/Dialect/Linalg/roundtrip.mlir

func.func @mixed_parallel_reduced_results(%arg0 : tensor<?x?x?xf32>,
   } -> (tensor<?x?x?xf32>, tensor<?x?xf32>)
   return %0#0, %0#1 : tensor<?x?x?xf32>, tensor<?x?xf32>
 }
 // CHECK-LABEL: func @mixed_parallel_reduced_results
 //       CHECK:     linalg.generic
 
 // -----
 
+func.func @map_no_inputs(%init: tensor<64xf32>) -> tensor<64xf32> {
+   %add = linalg.map
+      outs(%init:tensor<64xf32>)
+      () {
+        %0 = arith.constant 0.0: f32
+        linalg.yield %0: f32
+      }
+  func.return %add : tensor<64xf32>
+}
+// CHECK-LABEL: func @map_no_inputs
+//       CHECK:   linalg.map
+//  CHECK-NEXT:   outs
+//  CHECK-NEXT:   () {
+//  CHECK-NEXT:     arith.constant
+//  CHECK-NEXT:     linalg.yield
+//  CHECK-NEXT:   }
+
+// -----
+
 func.func @map_binary(%lhs: tensor<64xf32>, %rhs: tensor<64xf32>,
                       %init: tensor<64xf32>) -> tensor<64xf32> {
    %add = linalg.map
           ins(%lhs, %rhs: tensor<64xf32>, tensor<64xf32>)
           outs(%init:tensor<64xf32>)
           (%lhs_elem: f32, %rhs_elem: f32) {
             %0 = arith.addf %lhs_elem, %rhs_elem: f32
             linalg.yield %0: f32