src/hotspot/share/opto/macro.cpp

*** 346,355 ****
--- 346,356 ----
      bt = T_OBJECT;
      type = ftype->make_oopptr();
    }
    Node* res = NULL;
    if (ac->is_clonebasic()) {
+     assert(ac->in(ArrayCopyNode::Src) != ac->in(ArrayCopyNode::Dest), "clone source equals destination");
      Node* base = ac->in(ArrayCopyNode::Src)->in(AddPNode::Base);
      Node* adr = _igvn.transform(new AddPNode(base, base, MakeConX(offset)));
      const TypePtr* adr_type = _igvn.type(base)->is_ptr()->add_offset(offset);
      res = LoadNode::make(_igvn, ctl, mem, adr, adr_type, type, bt, MemNode::unordered, LoadNode::UnknownControl);
    } else {
*** 364,373 ****
--- 365,378 ----
  
        Node* off = _igvn.transform(new AddXNode(MakeConX(offset), diff));
        Node* base = ac->in(ArrayCopyNode::Src);
        Node* adr = _igvn.transform(new AddPNode(base, base, off));
        const TypePtr* adr_type = _igvn.type(base)->is_ptr()->add_offset(offset);
+       if (ac->in(ArrayCopyNode::Src) == ac->in(ArrayCopyNode::Dest)) {
+         // Don't emit a new load from src if src == dst but try to get the value from memory instead
+         return value_from_mem(ac->in(TypeFunc::Memory), ctl, ft, ftype, adr_type->isa_oopptr(), alloc);
+       }
        res = LoadNode::make(_igvn, ctl, mem, adr, adr_type, type, bt, MemNode::unordered, LoadNode::UnknownControl);
      }
    }
    if (res != NULL) {
      res = _igvn.transform(res);
*** 495,505 ****
    Node *alloc_ctrl = alloc->in(TypeFunc::Control);
    Node *alloc_mem = alloc->in(TypeFunc::Memory);
    Arena *a = Thread::current()->resource_area();
    VectorSet visited(a);
  
- 
    bool done = sfpt_mem == alloc_mem;
    Node *mem = sfpt_mem;
    while (!done) {
      if (visited.test_set(mem->_idx)) {
        return NULL;  // found a loop, give up
--- 500,509 ----