[mlir][linalg][transform] Fix printing of TileToForall in edge case.

[ingomueller-net]

Summary

The static_(num_threads|tile_sizes) attributes of this op are
DefaultValuedOptionalAttrs, so they can be constructed *without* such
an attribute. In other words, the following is a valid op (note the
absense of the static_num_threads attribute):

"builtin.module"() ({

"transform.sequence"() <{failure_propagation_mode = 1 : i32, operand_segment_sizes = array<i32: 0, 0>}> ({
^bb0(%arg0: !pdl.operation, %arg1: !transform.op<"linalg.matmul">, %arg2: !transform.op<"linalg.elemwise_binary">):
  %0 = "transform.structured.match"(%arg0) <{ops = ["test.dummy"]}> : (!pdl.operation) -> !pdl.operation
  %1:2 = "transform.structured.tile_to_forall_op"(%arg1, %0) <{operand_segment_sizes = array<i32: 1, 0, 0, 0, 1>}> : (!transform.op<"linalg.matmul">, !pdl.operation) -> (!transform.op<"scf.forall">, !transform.op<"linalg.matmul">)
  "transform.yield"() : () -> ()
}) : () -> ()

}) : () -> ()

However, the custom printing directive converted those to an ArrayRef,
which crashes if done on an empty ArrayAttr. This patch changes the
signature such that no automatic conversion takes place and extends the
test to test for existinnce of the attribute.

mlir/include/mlir/Dialect/Transform/Utils/Utils.h

 /// or the other two parameters may be specified.
 ///
 /// This allows idiomatic printing of mixed value and integer attributes in a
 /// list or with a single handle. E.g., `[%arg0 : !transform.any_op, 7, 42,
 /// %arg42 : !transform.param<i64>]` or just `%h : !transform.any_op`.
 void printPackedOrDynamicIndexList(OpAsmPrinter &printer, Operation *op,
                                    Value packed, Type packedType,
                                    OperandRange values, TypeRange valueTypes,
-                                   ArrayRef<int64_t> integers);
+                                   DenseI64ArrayAttr integers);
 
 /// Parser hook for custom directive in assemblyFormat.
 ///
 ///   custom<PackedOrDynamicIndexList>($packed, type($packed), $values,
 ///       type($values), $integers)
 ///
 /// See `printPackedOrDynamicIndexList` for details.
 ParseResult parsePackedOrDynamicIndexList(
     OpAsmParser &parser, std::optional<OpAsmParser::UnresolvedOperand> &packed,
     Type &packedType, SmallVectorImpl<OpAsmParser::UnresolvedOperand> &values,
     SmallVectorImpl<Type> &valueTypes, DenseI64ArrayAttr &integers);
 } // namespace transform
 } // namespace mlir
 
 #endif // MLIR_DIALECT_TRANSFORMS_UTILS_UTILS_H

mlir/lib/Dialect/Transform/Utils/Utils.cpp

 #include "mlir/IR/OpDefinition.h"
 #include "mlir/Interfaces/ViewLikeInterface.h"
 
 using namespace mlir;
 using namespace mlir::transform;
 
 void mlir::transform::printPackedOrDynamicIndexList(
     OpAsmPrinter &printer, Operation *op, Value packed, Type packedType,
-    OperandRange values, TypeRange valueTypes, ArrayRef<int64_t> integers) {
+    OperandRange values, TypeRange valueTypes, DenseI64ArrayAttr integers) {
   if (packed) {
-    assert(values.empty() && integers.empty() && "expected no values/integers");
+    assert(values.empty() && (!integers || integers.empty()) &&
+           "expected no values/integers");
     printer << "*(" << packed << " : " << packedType << ")";
     return;
   }
   printDynamicIndexList(printer, op, values, integers, valueTypes);
 }
 
 ParseResult mlir::transform::parsePackedOrDynamicIndexList(
     OpAsmParser &parser, std::optional<OpAsmParser::UnresolvedOperand> &packed,