src/cpu/x86/vm/assembler_x86_64.cpp

*** 4425,4437 ****
  void MacroAssembler::store_check_part_2(Register obj) {
    BarrierSet* bs = Universe::heap()->barrier_set();
    assert(bs->kind() == BarrierSet::CardTableModRef, "Wrong barrier set kind");
    CardTableModRefBS* ct = (CardTableModRefBS*)bs;
    assert(sizeof(*ct->byte_map_base) == sizeof(jbyte), "adjust this code");
!   ExternalAddress cardtable((address)ct->byte_map_base);
    Address index(noreg, obj, Address::times_1);
    movb(as_Address(ArrayAddress(cardtable, index)), 0);
  }
  
  void MacroAssembler::c2bool(Register x) {
    // implements x == 0 ? 0 : 1
    // note: must only look at least-significant byte of x
--- 4425,4460 ----
  void MacroAssembler::store_check_part_2(Register obj) {
    BarrierSet* bs = Universe::heap()->barrier_set();
    assert(bs->kind() == BarrierSet::CardTableModRef, "Wrong barrier set kind");
    CardTableModRefBS* ct = (CardTableModRefBS*)bs;
    assert(sizeof(*ct->byte_map_base) == sizeof(jbyte), "adjust this code");
! 
!   // The calculation for byte_map_base is as follows:
!   // byte_map_base = _byte_map - (uintptr_t(low_bound) >> card_shift);
!   // So this essentially converts an address to a displacement and
!   // it will never need to be relocated. On 64bit however the value may be too
!   // large for a 32bit displacement
! 
!   intptr_t disp = (intptr_t) ct->byte_map_base;
!   if (is_simm32(disp)) {
!     Address cardtable(noreg, obj, Address::times_1, disp);
!     movb(cardtable, 0);
!   } else {
!     // By doing it as an ExternalAddress disp could be converted to a rip-relative
!     // displacement and done in a single instruction given favorable mapping and
!     // a smarter version of as_Address. Worst case it is two instructions which
!     // is no worse off then loading disp into a register and doing as a simple
!     // Address() as above.
!     // We can't do as ExternalAddress as the only style since if disp == 0 we'll
!     // assert since NULL isn't acceptable in a reloci (see 6644928). In any case
!     // in some cases we'll get a single instruction version.
! 
!     ExternalAddress cardtable((address)disp);
      Address index(noreg, obj, Address::times_1);
      movb(as_Address(ArrayAddress(cardtable, index)), 0);
+   }
+ 
  }
  
  void MacroAssembler::c2bool(Register x) {
    // implements x == 0 ? 0 : 1
    // note: must only look at least-significant byte of x