Optimization of Box nodes in uncommon_trap

JDK-8075052 has removed useless autobox. However, in some cases, the box is still saved. For instance:

@Benchmark
public void testMethod(Blackhole bh) {
  int sum = 0;
  for (int i = 0; i < data.length; i++) {
      Integer ii = Integer.valueOf(data[i]);
      if (i < data.length) {
          sum += ii.intValue();
      }
  }
  bh.consume(sum);
}

Although the variable ii is only used at ii.intValue(), it cannot be eliminated as a result of being used by a hidden uncommon_trap.
The uncommon_trap is generated by the optimized "if", because its condition is always true.

We can postpone box in uncommon_trap in this situation. We treat box as a scalarized object by adding a SafePointScalarObjectNode in the uncommon_trap node,
and deleting the use of box:

```
@@ -603,6 +603,51 @@ void CallGenerator::do_late_inline_helper() {
     C->remove_macro_node(call);
   }
 
+ if (callprojs.resproj != NULL && call->is_CallStaticJava() &&
+ call->as_CallStaticJava()->is_boxing_method()) {
+ GraphKit kit(call->jvms());
+ PhaseGVN& gvn = kit.gvn();
+
+ Node_List delay_boxes;
+ bool no_use = true;
+ for (DUIterator_Fast imax, i = callprojs.resproj->fast_outs(imax); i < imax; i++) {
+ Node* m = callprojs.resproj->fast_out(i);
+ if (m->is_CallStaticJava() &&
+ m->as_CallStaticJava()->uncommon_trap_request() != 0) {
+ delay_boxes.push(m);
+ } else {
+ no_use = false;
+ break;
+ }
+ }
+
+ if (no_use) {
+ // delay box node in uncommon_trap runtime, treat box as a scalarized object
+ while (delay_boxes.size() > 0) {
+ ProjNode* res = callprojs.resproj->as_Proj();
+ Node* uncommon_trap_node = delay_boxes.pop();
+ int in_edge = uncommon_trap_node->find_edge(res);
+ assert(in_edge > 0, "sanity");
+
+ ciInstanceKlass* klass = call->as_CallStaticJava()->method()->holder();
+ int n_fields = klass->nof_nonstatic_fields();
+ assert(n_fields == 1, "sanity");
+
+ uint first_ind = (uncommon_trap_node->req() - uncommon_trap_node->jvms()->scloff());
+ Node* sobj = new SafePointScalarObjectNode(gvn.type(res)->isa_oopptr(),
+#ifdef ASSERT
+ NULL,
+#endif // ASSERT
+ first_ind, n_fields);
+ sobj->init_req(0, C->root());
+ uncommon_trap_node->add_req(call->in(res->_con));
+ sobj = gvn.transform(sobj);
+ uncommon_trap_node->jvms()->set_endoff(uncommon_trap_node->req());
+ uncommon_trap_node->set_req(in_edge, sobj);
+ }
+ }
+ }
+
```
It is shown in the following table that the patch improves the performance on x64 and aarch64.
The following table shows results of the performance test on x64 and aarch64:
x64:
base:
Benchmark Mode Samples Score Score error Units
o.s.MyBenchmark.testMethod avgt 30 50.374 3.927 us/op
delay box in uncommon_trap:
Benchmark Mode Samples Score Score error Units
o.s.MyBenchmark.testMethod avgt 30 4.571 0.004 us/op
aarch64:
base:
Benchmark Mode Samples Score Score error Units
o.s.MyBenchmark.testMethod avgt 30 51.782 0.357 us/op
delay box in uncommon_trap:
Benchmark Mode Samples Score Score error Units
o.s.MyBenchmark.testMethod avgt 30 3.876 0.002 us/op

There is no additional fail/error(s) of jtreg after this patch.