8276105: C2: Conv(D|F)2(I|L)Nodes::Ideal should handle rounding correctly

Reviewed-by: kvn, thartmann

Author: shipilev

src/hotspot/share/opto/convertnode.cpp

@@ -108,8 +108,10 @@ const Type* ConvD2INode::Value(PhaseGVN* phase) const {
 //------------------------------Ideal------------------------------------------
 // If converting to an int type, skip any rounding nodes
 Node *ConvD2INode::Ideal(PhaseGVN *phase, bool can_reshape) {
-  if( in(1)->Opcode() == Op_RoundDouble )
-  set_req(1,in(1)->in(1));
+  if (in(1)->Opcode() == Op_RoundDouble) {
+    set_req(1, in(1)->in(1));
+    return this;
+  }
   return NULL;
 }
 
@@ -142,8 +144,10 @@ Node* ConvD2LNode::Identity(PhaseGVN* phase) {
 //------------------------------Ideal------------------------------------------
 // If converting to an int type, skip any rounding nodes
 Node *ConvD2LNode::Ideal(PhaseGVN *phase, bool can_reshape) {
-  if( in(1)->Opcode() == Op_RoundDouble )
-  set_req(1,in(1)->in(1));
+  if (in(1)->Opcode() == Op_RoundDouble) {
+    set_req(1, in(1)->in(1));
+    return this;
+  }
   return NULL;
 }
 
@@ -179,8 +183,10 @@ Node* ConvF2INode::Identity(PhaseGVN* phase) {
 //------------------------------Ideal------------------------------------------
 // If converting to an int type, skip any rounding nodes
 Node *ConvF2INode::Ideal(PhaseGVN *phase, bool can_reshape) {
-  if( in(1)->Opcode() == Op_RoundFloat )
-  set_req(1,in(1)->in(1));
+  if (in(1)->Opcode() == Op_RoundFloat) {
+    set_req(1, in(1)->in(1));
+    return this;
+  }
   return NULL;
 }
 
@@ -206,8 +212,10 @@ Node* ConvF2LNode::Identity(PhaseGVN* phase) {
 //------------------------------Ideal------------------------------------------
 // If converting to an int type, skip any rounding nodes
 Node *ConvF2LNode::Ideal(PhaseGVN *phase, bool can_reshape) {
-  if( in(1)->Opcode() == Op_RoundFloat )
-  set_req(1,in(1)->in(1));
+  if (in(1)->Opcode() == Op_RoundFloat) {
+    set_req(1, in(1)->in(1));
+    return this;
+  }
   return NULL;
 }