!6339 fix strided slice infershape error when stride is negative

Merge pull request !6339 from zhaozhenlong/lite/issue/stride_neg_infershape

mindspore/lite/src/ops/strided_slice.cc

@@ -226,6 +226,17 @@ void StridedSlice::ApplyEndMask() {
   }
 }
 
+void StridedSlice::TransIndexToPositive() {
+  for (int i = 0; i < static_cast<int>(begins_.size()); ++i) {
+    if (begins_.at(i) < 0) {
+      begins_.at(i) += in_shape_.at(i);
+    }
+    if (ends_.at(i) < 0) {
+      ends_.at(i) += in_shape_.at(i);
+    }
+  }
+}
+
 int StridedSlice::InferShape(std::vector<lite::Tensor *> inputs, std::vector<lite::Tensor *> outputs) {
   MS_ASSERT(this->primitive_ != nullptr);
   if (outputs.size() != kStridedSliceOutputNum) {
@@ -266,7 +277,7 @@ int StridedSlice::InferShape(std::vector<lite::Tensor *> inputs, std::vector<lit
       return RET_INFER_ERR;
     }
     ndim_ = begin_tensor->ElementsNum();
-    for (int i=0; i< ndim_; ++i) {
+    for (int i = 0; i < ndim_; ++i) {
       in_shape_.emplace_back(input_shape.at(i));
       begins_.emplace_back(begin_data[i]);
       ends_.emplace_back(end_data[i]);
@@ -297,13 +308,13 @@ int StridedSlice::InferShape(std::vector<lite::Tensor *> inputs, std::vector<lit
 
   output_shape.clear();
   output_shape.resize(in_shape_.size());
+
+  TransIndexToPositive();
   for (int i = 0; i < static_cast<int>(in_shape_.size()); i++) {
     if (i < ndim_ && new_axis_mask_.at(i)) {
       output_shape.at(i) = 1;
-    } else if (ends_.at(i) > 0) {
-      output_shape.at(i) = (ends_.at(i) - begins_.at(i)) / strides_.at(i);
     } else {
-      output_shape.at(i) = (input_shape.at(i) + ends_.at(i) - begins_.at(i)) % input_shape.at(i) / strides_.at(i);
+      output_shape.at(i) = (ends_.at(i) - begins_.at(i)) / strides_.at(i);
     }
   }
 

mindspore/lite/src/ops/strided_slice.h

@@ -80,6 +80,7 @@ class StridedSlice : public PrimitiveC {
   std::vector<bool> ellipsis_mask_;
   std::vector<bool> new_axis_mask_;
   std::vector<bool> shrink_axis_mask_;
+  void TransIndexToPositive();
 };
 }  // namespace lite
 }  // namespace mindspore