src/cpu/x86/vm/macroAssembler_x86.cpp

rev 10501 : [backport] Check heap stability in C1 WBs
rev 10524 : [backport] Some trivial-ish cleanups
rev 10557 : [backport] Assembler write barriers should consistently check for forwarded objects

*** 3748,3758 ****
  void MacroAssembler::null_check(Register reg, int offset) {
    if (needs_explicit_null_check(offset)) {
      // provoke OS NULL exception if reg = NULL by
      // accessing M[reg] w/o changing any (non-CC) registers
      // NOTE: cmpl is plenty here to provoke a segv
- 
      cmpptr(rax, Address(reg, 0));
      // Note: should probably use testl(rax, Address(reg, 0));
      //       may be shorter code (however, this version of
      //       testl needs to be implemented first)
    } else {
--- 3748,3757 ----
*** 4447,4465 ****
  void MacroAssembler::shenandoah_write_barrier(Register dst) {
    assert(UseShenandoahGC && ShenandoahWriteBarrier, "Should be enabled");
  
    Label done;
  
-   // Check for evacuation-in-progress
    Address gc_state(r15_thread, in_bytes(JavaThread::gc_state_offset()));
-   testb(gc_state, ShenandoahHeap::EVACUATION);
  
!   // The read-barrier.
    if (ShenandoahWriteBarrierRB) {
      movptr(dst, Address(dst, BrooksPointer::byte_offset()));
    }
  
    jccb(Assembler::zero, done);
  
    if (dst != rax) {
      xchgptr(dst, rax); // Move obj into rax and save rax into obj.
    }
--- 4446,4468 ----
  void MacroAssembler::shenandoah_write_barrier(Register dst) {
    assert(UseShenandoahGC && ShenandoahWriteBarrier, "Should be enabled");
  
    Label done;
  
    Address gc_state(r15_thread, in_bytes(JavaThread::gc_state_offset()));
  
!   // Check for heap stability
!   testb(gc_state, ShenandoahHeap::HAS_FORWARDED | ShenandoahHeap::EVACUATION);
!   jccb(Assembler::zero, done);
! 
!   // Heap is unstable, need to perform the read-barrier even if WB is inactive
    if (ShenandoahWriteBarrierRB) {
      movptr(dst, Address(dst, BrooksPointer::byte_offset()));
    }
  
+   // Check for evacuation-in-progress and jump to WB slow-path if needed
+   testb(gc_state, ShenandoahHeap::EVACUATION);
    jccb(Assembler::zero, done);
  
    if (dst != rax) {
      xchgptr(dst, rax); // Move obj into rax and save rax into obj.
    }