Add support for the onnx.SequenceLength op. (#3362)

include/torch-mlir/Conversion/TorchOnnxToTorch/Patterns.h

@@ -97,6 +97,19 @@ struct OpBinder {
     return success();
   }
 
+  // Operand matches of different arities.
+  ParseResult tensorListOperand(Value &value0) {
+    if (op->getNumOperands() != 1)
+      return failure();
+    value0 = op->getOperand(0);
+    auto tt = dyn_cast<Torch::ListType>(value0.getType());
+    if (!tt)
+      return failure();
+    if (!toValidTensorType(tt.getContainedType()))
+      return failure();
+    return success();
+  }
+
   ParseResult tensorListResultType(Torch::ListType &type0) {
     if (op->getNumResults() != 1)
       return failure();

lib/Conversion/TorchOnnxToTorch/DefaultDomainQtoZ.cpp

@@ -532,6 +532,30 @@ void mlir::torch::onnx_c::populateDefaultDomainQtoZ(
             binder.op, resultType, operands);
         return success();
       });
+  patterns.onOp(
+      "SequenceLength", 11,
+      [](OpBinder binder, ConversionPatternRewriter &rewriter) {
+        // onnx.SequenceLength takes a sequence(list) of tensors, and returns
+        // a zero rank tensor with the length.
+        Torch::ValueTensorType resultType;
+        Value x;
+        if (binder.tensorListOperand(x) || binder.tensorResultType(resultType))
+          return failure();
+
+        Value cstFalse =
+            rewriter.create<Torch::ConstantBoolOp>(binder.getLoc(), false);
+        Value none = rewriter.create<Torch::ConstantNoneOp>(binder.getLoc());
+
+        Value len = rewriter.create<Torch::AtenLenTOp>(
+            binder.getLoc(), rewriter.getType<Torch::IntType>(), x);
+
+        // AtenLenTOp returns a torch.int, so we have to
+        // put that in a tensor.
+        rewriter.replaceOpWithNewOp<Torch::AtenTensorIntOp>(
+            binder.op, resultType, len, none, none, cstFalse);
+
+        return success();
+      });
   patterns.onOp(
       "Sigmoid", 1, [](OpBinder binder, ConversionPatternRewriter &rewriter) {
         Torch::ValueTensorType resultType;

test/Conversion/TorchOnnxToTorch/simple_ops_q_to_z.mlir

@@ -2099,6 +2099,21 @@ module {
 
 // -----
 
+// CHECK-LABEL: func.func @test_sequence_length
+module {
+  func.func @test_sequence_length(%arg0: !torch.list<vtensor<[?,?,?],f32>>) ->  !torch.vtensor<[],si64> attributes {torch.onnx_meta.ir_version = 8 : si64, torch.onnx_meta.opset_version = 17 : si64, torch.onnx_meta.producer_name = "backend-test", torch.onnx_meta.producer_version = ""} {
+// CHECK: %[[FALSE:.+]] = torch.constant.bool false
+// CHECK: %[[NONE:.+]] = torch.constant.none
+// CHECK: %[[LEN:.+]] = torch.aten.len.t %arg0 : !torch.list<vtensor<[?,?,?],f32>> -> !torch.int
+// CHECK: %[[LEN_AS_TEN:.+]] = torch.aten.tensor.int %[[LEN]],  %[[NONE]],  %[[NONE]], %[[FALSE]] : !torch.int, !torch.none, !torch.none, !torch.bool -> !torch.vtensor<[],si64>
+// CHECK: return %[[LEN_AS_TEN]] : !torch.vtensor<[],si64>
+    %0 = torch.operator "onnx.SequenceLength"(%arg0) : (!torch.list<vtensor<[?,?,?],f32>>) -> !torch.vtensor<[],si64>
+    return %0 : !torch.vtensor<[],si64>
+  }
+}
+
+// -----
+
 // CHECK-LABEL: func.func @test_sce_mean_3d
 func.func @test_sce_mean_3d(%arg0: !torch.vtensor<[3,5,2],f32>, %arg1: !torch.vtensor<[3,2],si64>) -> !torch.vtensor<[],f32> attributes {torch.onnx_meta.ir_version = 7 : si64, torch.onnx_meta.opset_version = 13 : si64, torch.onnx_meta.producer_name = "backend-test", torch.onnx_meta.producer_version = ""} {
   // CHECK: %[[NONE:.+]] = torch.constant.none