[mlir] properly handle an edge case in transform.split_handles

The `transform.split_handles` transform op has an edge case that is
supposed to propagate empty handle state to all resulting handles
regardless of their number. Actually set empty payload for them instead
of leaving them unset.

Reviewed By: springerm

Differential Revision: https://reviews.llvm.org/D149652

Author: ftynse

mlir/lib/Dialect/Transform/IR/TransformOps.cpp

@@ -1510,13 +1510,17 @@ transform::SplitHandlesOp::apply(transform::TransformResults &results,
   if (numResultHandles != expectedNumResultHandles) {
     // Empty input handle corner case: always propagates empty handles in both
     // suppress and propagate modes.
-    if (numResultHandles == 0)
+    if (numResultHandles == 0) {
+      for (OpResult result : getResults())
+        results.set(result, {});
       return DiagnosedSilenceableFailure::success();
+    }
+
     // If the input handle was not empty and the number of result handles does
     // not match, this is a legit silenceable error.
     return emitSilenceableError()
            << getHandle() << " expected to contain " << expectedNumResultHandles
-           << " operation handles but it only contains " << numResultHandles
+           << " operation handles but it contains " << numResultHandles
            << " handles";
   }
   // Normal successful case.

mlir/test/Dialect/Transform/test-interpreter.mlir

@@ -831,7 +831,7 @@ transform.sequence failures(propagate) {
   // expected-remark @below {{1}}
   transform.test_print_number_of_associated_payload_ir_ops %h#0
   %muli_2 = transform.structured.match ops{["arith.muli"]} in %fun : (!pdl.operation) -> !pdl.operation
-  // expected-error @below {{expected to contain 3 operation handles but it only contains 2 handles}}
+  // expected-error @below {{expected to contain 3 operation handles but it contains 2 handles}}
   %h_2:3 = split_handles %muli_2 in [3] : (!pdl.operation) -> (!pdl.operation, !pdl.operation, !pdl.operation)
 }
 
@@ -975,7 +975,7 @@ func.func @split_handles(%a: index, %b: index, %c: index) {
 transform.sequence -> !pdl.operation failures(propagate) {
 ^bb1(%fun: !pdl.operation):
   %muli = transform.structured.match ops{["arith.muli"]} in %fun : (!pdl.operation) -> !pdl.operation
-  // expected-error @below {{expected to contain 3 operation handles but it only contains 2 handles}}
+  // expected-error @below {{expected to contain 3 operation handles but it contains 2 handles}}
   %h_2:3 = split_handles %muli in [3] : (!pdl.operation) -> (!pdl.operation, !pdl.operation, !pdl.operation)
   /// Test that yield does not crash in the presence of silenceable error in
   /// propagate mode.
@@ -984,6 +984,17 @@ transform.sequence -> !pdl.operation failures(propagate) {
 
 // -----
 
+transform.sequence -> !transform.any_op failures(suppress) {
+^bb0(%arg0: !transform.any_op):
+  %muli = transform.structured.match ops{["arith.muli"]} in %arg0 : (!transform.any_op) -> !transform.any_op
+  // Edge case propagating empty handles in splitting.
+  %0:3 = split_handles %muli in [3] : (!transform.any_op) -> (!transform.any_op, !transform.any_op, !transform.any_op)
+  // Test does not crash when accessing the empty handle.
+  yield %0#0 : !transform.any_op
+}
+
+// -----
+
 transform.sequence failures(propagate) {
 ^bb0(%arg0: !transform.any_op):
   %0 = transform.test_produce_integer_param_with_type i32 : !transform.test_dialect_param