src/share/vm/opto/lcm.cpp

rev 12685 : 8176518: [9] C2: Invalid ImplicitNullChecks with non-protected heap base
Reviewed-by:

*** 253,264 ****
        intptr_t offset = 0;
        const TypePtr *adr_type = NULL;  // Do not need this return value here
        const Node* base = mach->get_base_and_disp(offset, adr_type);
        if (base == NULL || base == NodeSentinel) {
          // Narrow oop address doesn't have base, only index
!         if( val->bottom_type()->isa_narrowoop() &&
!             MacroAssembler::needs_explicit_null_check(offset) )
            continue;             // Give up if offset is beyond page size
          // cannot reason about it; is probably not implicit null exception
        } else {
          const TypePtr* tptr;
          if (UseCompressedOops && (Universe::narrow_oop_shift() == 0 ||
--- 253,265 ----
        intptr_t offset = 0;
        const TypePtr *adr_type = NULL;  // Do not need this return value here
        const Node* base = mach->get_base_and_disp(offset, adr_type);
        if (base == NULL || base == NodeSentinel) {
          // Narrow oop address doesn't have base, only index
!         if (val->bottom_type()->isa_narrowoop() &&
!             (MacroAssembler::needs_explicit_null_check(offset) ||
!              !Universe::narrow_oop_use_implicit_null_checks()))
            continue;             // Give up if offset is beyond page size
          // cannot reason about it; is probably not implicit null exception
        } else {
          const TypePtr* tptr;
          if (UseCompressedOops && (Universe::narrow_oop_shift() == 0 ||
*** 268,282 ****
          } else {
            // only regular oops are expected here
            tptr = base->bottom_type()->is_ptr();
          }
          // Give up if offset is not a compile-time constant
!         if( offset == Type::OffsetBot || tptr->_offset == Type::OffsetBot )
            continue;
          offset += tptr->_offset; // correct if base is offseted
!         if( MacroAssembler::needs_explicit_null_check(offset) )
            continue;             // Give up is reference is beyond 4K page size
        }
      }
  
      // Check ctrl input to see if the null-check dominates the memory op
      Block *cb = get_block_for_node(mach);
--- 269,287 ----
          } else {
            // only regular oops are expected here
            tptr = base->bottom_type()->is_ptr();
          }
          // Give up if offset is not a compile-time constant
!         if (offset == Type::OffsetBot || tptr->_offset == Type::OffsetBot)
            continue;
          offset += tptr->_offset; // correct if base is offseted
!         if (MacroAssembler::needs_explicit_null_check(offset))
            continue;             // Give up is reference is beyond 4K page size
+         // Access to non-protected heap base
+         if (base->is_Mach() && base->as_Mach()->ideal_Opcode() == Op_DecodeN &&
+             !Universe::narrow_oop_use_implicit_null_checks())
+           continue;
        }
      }
  
      // Check ctrl input to see if the null-check dominates the memory op
      Block *cb = get_block_for_node(mach);