!4150 Enable the identity op can be eliminated in pynative mode

Merge pull request !4150 from JoyLvliang/enable-the-identity-op-can-be-eliminated-in-pynative-mode

mindspore/ccsrc/frontend/optimizer/irpass/arithmetic_simplify.cc

@@ -20,9 +20,6 @@ namespace mindspore {
 namespace opt {
 namespace irpass {
 AnfNodePtr ArithmeticSimplify::operator()(const OptimizerPtr &, const AnfNodePtr &node) {
-  if (MsContext::GetInstance()->execution_mode() == kPynativeMode) {
-    return nullptr;
-  }
   PatternNode x, y, z, xs;
   PConstant one_(node, false, 1);
   PConstant one_scalar_(node, false, 1, true);
@@ -32,14 +29,16 @@ AnfNodePtr ArithmeticSimplify::operator()(const OptimizerPtr &, const AnfNodePtr
   PConstant const_2(node);
   PConstant any_const(node);
 
-  MATCH_REPLACE(node, x + zero_, x);                                                           // Add by zero
-  MATCH_REPLACE(node, x + zero_scalar_, x);                                                    // Add by zero
-  MATCH_REPLACE(node, PBinOperation(prim::kPrimScalarAdd, x, zero_scalar_, true), x);          // Scalar Add by zero
-  MATCH_REPLACE_IF(node, x * one_, any_const.WithValueOf(x), !one_.CheckFunc(IsParam, node));  // Multiply by one
-  MATCH_REPLACE(node, PBinOperation(prim::kPrimScalarMul, x, one_scalar_, true), x);           // Scalar Mul by one
+  if (MsContext::GetInstance()->execution_mode() != kPynativeMode) {
+    MATCH_REPLACE(node, x + zero_, x);                                                           // Add by zero
+    MATCH_REPLACE(node, x + zero_scalar_, x);                                                    // Add by zero
+    MATCH_REPLACE(node, PBinOperation(prim::kPrimScalarAdd, x, zero_scalar_, true), x);          // Scalar Add by zero
+    MATCH_REPLACE_IF(node, x * one_, any_const.WithValueOf(x), !one_.CheckFunc(IsParam, node));  // Multiply by one
+    MATCH_REPLACE(node, PBinOperation(prim::kPrimScalarMul, x, one_scalar_, true), x);           // Scalar Mul by one
 
-  // Scalar Mul by zero
-  MATCH_REPLACE(node, PBinOperation(prim::kPrimScalarMul, x, zero_scalar_, true), zero_scalar_.NewValue());
+    // Scalar Mul by zero
+    MATCH_REPLACE(node, PBinOperation(prim::kPrimScalarMul, x, zero_scalar_, true), zero_scalar_.NewValue());
+  }
   // Prim Eliminate (identity)
   MATCH_REPLACE(node, PPrimitive(prim::kPrimIdentity, x), x);