remove kept flag after tensor is replaced or popped (#6759)

Author: pyu10055

tfjs-converter/src/executor/tensor_list.ts

@@ -143,6 +143,7 @@ export class TensorList {
     const outputElementShape =
         inferElementShape(this.elementShape, this.tensors, elementShape);
     const tensor = this.tensors.pop();
+    tensor.kept = false;
 
     assertShapesMatchAllowUndefinedSize(
         tensor.shape, elementShape, 'TensorList shape mismatch: ');
@@ -243,6 +244,12 @@ export class TensorList {
     assertShapesMatchAllowUndefinedSize(
         this.elementShape, tensor.shape, 'TensorList shape mismatch: ');
     keep(tensor);
+
+    // dispose the previous value if it is replacing.
+    if (this.tensors[elementIndex] != null) {
+      this.tensors[elementIndex].kept = false;
+    }
+
     this.tensors[elementIndex] = tensor;
   }
 

tfjs-converter/src/executor/tensor_list_test.ts

@@ -122,7 +122,8 @@ describe('TensorList', () => {
     it('should create no new tensors', () => {
       tensorList.pushBack(tensor);
       const numTensors = memory().numTensors;
-      tensorList.popBack(SHAPE, DTYPE);
+      const tensorPoped = tensorList.popBack(SHAPE, DTYPE);
+      expect(tensorPoped.kept).toBeFalsy();
       // a new reshaped tensor
       expect(memory().numTensors).toEqual(numTensors + 1);
     });
@@ -164,6 +165,14 @@ describe('TensorList', () => {
       tensorList.setItem(0, tensor);
       expect(memory().numTensors).toEqual(numTensors);
     });
+    it('should remove kept flag for replaced tensor', () => {
+      tensorList = new TensorList([], [-1, 1], DTYPE, SIZE);
+      tensorList.setItem(0, tensor);
+      expect(tensor.kept).toBeTruthy();
+      tensorList.setItem(0, tensor2);
+      expect(tensor.kept).toBeFalsy();
+      expect(tensor2.kept).toBeTruthy();
+    });
   });
 
   describe('getItem', () => {