src/hotspot/share/gc/shenandoah/c2/shenandoahBarrierSetC2.cpp

rev 56771 : 8233339: Shenandoah: Centralize load barrier decisions into ShenandoahBarrierSet

*** 533,590 ****
    return BarrierSetC2::store_at_resolved(access, val);
  }
  
  Node* ShenandoahBarrierSetC2::load_at_resolved(C2Access& access, const Type* val_type) const {
    DecoratorSet decorators = access.decorators();
  
    Node* adr = access.addr().node();
    Node* obj = access.base();
  
    bool mismatched = (decorators & C2_MISMATCHED) != 0;
    bool unknown = (decorators & ON_UNKNOWN_OOP_REF) != 0;
    bool on_heap = (decorators & IN_HEAP) != 0;
    bool on_weak_ref = (decorators & (ON_WEAK_OOP_REF | ON_PHANTOM_OOP_REF)) != 0;
    bool is_unordered = (decorators & MO_UNORDERED) != 0;
    bool need_cpu_mem_bar = !is_unordered || mismatched || !on_heap;
-   bool is_traversal_mode = ShenandoahHeap::heap()->is_traversal_mode();
-   bool keep_alive = (decorators & AS_NO_KEEPALIVE) == 0 || is_traversal_mode;
-   bool in_native = (decorators & IN_NATIVE) != 0;
  
    Node* top = Compile::current()->top();
  
    Node* offset = adr->is_AddP() ? adr->in(AddPNode::Offset) : top;
    Node* load = BarrierSetC2::load_at_resolved(access, val_type);
  
!   if (access.is_oop()) {
!     if (ShenandoahLoadRefBarrier) {
!       load = new ShenandoahLoadReferenceBarrierNode(NULL, load, in_native && !is_traversal_mode);
        if (access.is_parse_access()) {
          load = static_cast<C2ParseAccess &>(access).kit()->gvn().transform(load);
        } else {
          load = static_cast<C2OptAccess &>(access).gvn().transform(load);
        }
-     }
-   }
  
    // If we are reading the value of the referent field of a Reference
    // object (either by using Unsafe directly or through reflection)
    // then, if SATB is enabled, we need to record the referent in an
    // SATB log buffer using the pre-barrier mechanism.
    // Also we need to add memory barrier to prevent commoning reads
    // from this field across safepoint since GC can change its value.
!   bool need_read_barrier = ShenandoahKeepAliveBarrier &&
!     (on_weak_ref || (unknown && offset != top && obj != top));
! 
!   if (!access.is_oop() || !need_read_barrier) {
      return load;
    }
  
    assert(access.is_parse_access(), "entry not supported at optimization time");
    C2ParseAccess& parse_access = static_cast<C2ParseAccess&>(access);
    GraphKit* kit = parse_access.kit();
  
!   if (on_weak_ref && keep_alive) {
      // Use the pre-barrier to record the value in the referent field
      satb_write_barrier_pre(kit, false /* do_load */,
                             NULL /* obj */, NULL /* adr */, max_juint /* alias_idx */, NULL /* val */, NULL /* val_type */,
                             load /* pre_val */, T_OBJECT);
      // Add memory barrier to prevent commoning reads from this field
--- 533,590 ----
    return BarrierSetC2::store_at_resolved(access, val);
  }
  
  Node* ShenandoahBarrierSetC2::load_at_resolved(C2Access& access, const Type* val_type) const {
    DecoratorSet decorators = access.decorators();
+   BasicType type = access.type();
+ 
+   assert((decorators & AS_RAW) == 0, "Unexpected decorator");
+   assert((decorators & AS_NO_KEEPALIVE) == 0, "Unexpected decorator");
  
    Node* adr = access.addr().node();
    Node* obj = access.base();
  
    bool mismatched = (decorators & C2_MISMATCHED) != 0;
    bool unknown = (decorators & ON_UNKNOWN_OOP_REF) != 0;
    bool on_heap = (decorators & IN_HEAP) != 0;
    bool on_weak_ref = (decorators & (ON_WEAK_OOP_REF | ON_PHANTOM_OOP_REF)) != 0;
    bool is_unordered = (decorators & MO_UNORDERED) != 0;
    bool need_cpu_mem_bar = !is_unordered || mismatched || !on_heap;
  
    Node* top = Compile::current()->top();
  
    Node* offset = adr->is_AddP() ? adr->in(AddPNode::Offset) : top;
    Node* load = BarrierSetC2::load_at_resolved(access, val_type);
+   if (!ShenandoahBarrierSet::need_load_reference_barrier(decorators, type)) {
+     return load;
+   }
  
!   load = new ShenandoahLoadReferenceBarrierNode(NULL, load, ShenandoahBarrierSet::use_native_load_reference_barrier(decorators, type));
    if (access.is_parse_access()) {
      load = static_cast<C2ParseAccess &>(access).kit()->gvn().transform(load);
    } else {
      load = static_cast<C2OptAccess &>(access).gvn().transform(load);
    }
  
+   if (!ShenandoahBarrierSet::need_keep_alive_barrier(decorators, type)) {
+     return load;
+   }
    // If we are reading the value of the referent field of a Reference
    // object (either by using Unsafe directly or through reflection)
    // then, if SATB is enabled, we need to record the referent in an
    // SATB log buffer using the pre-barrier mechanism.
    // Also we need to add memory barrier to prevent commoning reads
    // from this field across safepoint since GC can change its value.
!   if (unknown && (offset == top || obj == top)) {
      return load;
    }
  
    assert(access.is_parse_access(), "entry not supported at optimization time");
    C2ParseAccess& parse_access = static_cast<C2ParseAccess&>(access);
    GraphKit* kit = parse_access.kit();
  
!   if (on_weak_ref) {
      // Use the pre-barrier to record the value in the referent field
      satb_write_barrier_pre(kit, false /* do_load */,
                             NULL /* obj */, NULL /* adr */, max_juint /* alias_idx */, NULL /* val */, NULL /* val_type */,
                             load /* pre_val */, T_OBJECT);
      // Add memory barrier to prevent commoning reads from this field