src/share/vm/opto/library_call.cpp

rev 5728 : 8029101: PPC64 (part 211): ordering of Independent Reads of Independent Writes
Contributed-by: mdoerr

*** 2625,2636 ****
      // volatile membars (for stores; compare Parse::do_put_xxx), which
      // we cannot do effectively here because we probably only have a
      // rough approximation of type.
      need_mem_bar = true;
      // For Stores, place a memory ordering barrier now.
!     if (is_store)
        insert_mem_bar(Op_MemBarRelease);
    }
  
    // Memory barrier to prevent normal and 'unsafe' accesses from
    // bypassing each other.  Happens after null checks, so the
    // exception paths do not take memory state from the memory barrier,
--- 2625,2641 ----
      // volatile membars (for stores; compare Parse::do_put_xxx), which
      // we cannot do effectively here because we probably only have a
      // rough approximation of type.
      need_mem_bar = true;
      // For Stores, place a memory ordering barrier now.
!     if (is_store) {
        insert_mem_bar(Op_MemBarRelease);
+     } else {
+       // Support ordering of "Independent Reads of Independent Writes" (see Parse::do_get_xxx).
+       // Solution: implement volatile read as sync-load-acquire
+       PPC64_ONLY(insert_mem_bar(Op_MemBarVolatile));
+     }
    }
  
    // Memory barrier to prevent normal and 'unsafe' accesses from
    // bypassing each other.  Happens after null checks, so the
    // exception paths do not take memory state from the memory barrier,
*** 2715,2728 ****
        }
      }
    }
  
    if (is_volatile) {
!     if (!is_store)
        insert_mem_bar(Op_MemBarAcquire);
!     else
!       insert_mem_bar(Op_MemBarVolatile);
    }
  
    if (need_mem_bar) insert_mem_bar(Op_MemBarCPUOrder);
  
    return true;
--- 2720,2735 ----
        }
      }
    }
  
    if (is_volatile) {
!     if (!is_store) {
        insert_mem_bar(Op_MemBarAcquire);
!     } else {
!       // Changed volatiles/Unsafe: lwsync-store, sync-load-acquire.
!       NOT_PPC64(insert_mem_bar(Op_MemBarVolatile));
!     }
    }
  
    if (need_mem_bar) insert_mem_bar(Op_MemBarCPUOrder);
  
    return true;