src/share/vm/opto/superword.cpp

*** 1686,1696 ****
      Node *n = lp()->fast_out(i);
      if (in_bb(n) && (n->is_Phi() && n->bottom_type() == Type::MEMORY)) {
        Node* n_tail  = n->in(LoopNode::LoopBackControl);
        if (n_tail != n->in(LoopNode::EntryControl)) {
          if (!n_tail->is_Mem()) {
!           assert(n_tail->is_Mem(), err_msg_res("unexpected node for memory slice: %s", n_tail->Name()));
            return false; // Bailout
          }
          _mem_slice_head.push(n);
          _mem_slice_tail.push(n_tail);
        }
--- 1686,1696 ----
      Node *n = lp()->fast_out(i);
      if (in_bb(n) && (n->is_Phi() && n->bottom_type() == Type::MEMORY)) {
        Node* n_tail  = n->in(LoopNode::LoopBackControl);
        if (n_tail != n->in(LoopNode::EntryControl)) {
          if (!n_tail->is_Mem()) {
!           assert(n_tail->is_Mem() || n_tail == n, err_msg_res("unexpected node for memory slice: %s", n_tail->Name()));
            return false; // Bailout
          }
          _mem_slice_head.push(n);
          _mem_slice_tail.push(n_tail);
        }
*** 2315,2324 ****
--- 2315,2345 ----
    //unsafe reference could not be aligned appropriately without runtime checking
    if (base == NULL || base->bottom_type() == Type::TOP) {
      assert(!valid(), "unsafe access");
      return;
    }
+   if (UseShenandoahGC) {
+     // Detect a Shenandoah write barrier between the pre and main loop
+     // (which could break loop alignment code)
+     CountedLoopNode *main_head = slp->lp()->as_CountedLoop();
+     if (main_head->is_main_loop()) {
+       Node* c = main_head->in(LoopNode::EntryControl)->in(0)->in(0)->in(0);
+       if (!c->is_CountedLoopEnd()) {
+         // in case of a reserve copy
+         c = c->in(0)->in(0);
+         assert(c->is_CountedLoopEnd(), "where's the pre loop?");
+       }
+       CountedLoopEndNode* pre_end = c->as_CountedLoopEnd();
+       CountedLoopNode* pre_loop = pre_end->loopnode();
+       assert(pre_loop->is_pre_loop(), "where's the pre loop?");
+       
+       Node* base_c = phase()->get_ctrl(base);
+       if (!phase()->is_dominator(base_c, pre_loop)) {
+         return;
+       }
+     }
+   }
    for (int i = 0; i < 3; i++) {
      if (!scaled_iv_plus_offset(adr->in(AddPNode::Offset))) {
        assert(!valid(), "too complex");
        return;
      }