RFR(XL): 8224675: Late GC barrier insertion for ZGC

[Per Liden]

Hi Nils,

We should now also be able to remove the following ugly hacks (yay!):

diff --git a/src/hotspot/share/classfile/vmSymbols.cpp 
b/src/hotspot/share/classfile/vmSymbols.cpp
--- a/src/hotspot/share/classfile/vmSymbols.cpp
+++ b/src/hotspot/share/classfile/vmSymbols.cpp
@@ -778,9 +778,6 @@
  #endif // COMPILER1
  #ifdef COMPILER2
    case vmIntrinsics::_clone:
-#if INCLUDE_ZGC
-    if (UseZGC) return true;
-#endif
    case vmIntrinsics::_copyOf:
    case vmIntrinsics::_copyOfRange:
      // These intrinsics use both the objectcopy and the arraycopy
diff --git a/src/hotspot/share/gc/z/c2/zBarrierSetC2.cpp 
b/src/hotspot/share/gc/z/c2/zBarrierSetC2.cpp
--- a/src/hotspot/share/gc/z/c2/zBarrierSetC2.cpp
+++ b/src/hotspot/share/gc/z/c2/zBarrierSetC2.cpp
@@ -462,7 +462,6 @@
    }

    bool weak = (access.decorators() & ON_WEAK_OOP_REF) != 0;
-  assert(access.is_parse_access(), "entry not supported at optimization 
time");
    if (p->isa_Load()) {
      p->as_Load()->set_barrier(weak);
    }
diff --git a/src/hotspot/share/runtime/stackValue.cpp 
b/src/hotspot/share/runtime/stackValue.cpp
--- a/src/hotspot/share/runtime/stackValue.cpp
+++ b/src/hotspot/share/runtime/stackValue.cpp
@@ -133,11 +133,6 @@
        }
  #endif
        // Deoptimization must make sure all oops have passed load barriers
-#if INCLUDE_ZGC
-      if (UseZGC) {
-        val = 
ZBarrier::load_barrier_on_oop_field_preloaded((oop*)value_addr, val);
-      }
-#endif
  #if INCLUDE_SHENANDOAHGC
        if (UseShenandoahGC) {
          val = 
ShenandoahBarrierSet::barrier_set()->load_reference_barrier(val);

cheers,
Per

On 5/24/19 11:41 AM, Nils Eliasson wrote:
> Hi Per,
> 
> I removed the code and updated the webrev.
> 
> Thanks,
> 
> Nils
> 
> On 2019-05-23 21:32, Per Liden wrote:
>> Hi Nils,
>>
>> On 2019-05-23 16:25, Nils Eliasson wrote:
>> [...]
>>> The wart that was fixup_partial_loads in zHeap has also been made 
>>> redundant.
>>
>> We should also be able to remove the function, task and closure for this:
>>
>>  327 class ZFixupPartialLoadsClosure : public ZRootsIteratorClosure {
>>  328 public:
>>  329   virtual void do_oop(oop* p) {
>>  330     ZBarrier::mark_barrier_on_root_oop_field(p);
>>  331   }
>>  332
>>  333   virtual void do_oop(narrowOop* p) {
>>  334     ShouldNotReachHere();
>>  335   }
>>  336 };
>>  337
>>  338 class ZFixupPartialLoadsTask : public ZTask {
>>  339 private:
>>  340   ZThreadRootsIterator _thread_roots;
>>  341
>>  342 public:
>>  343   ZFixupPartialLoadsTask() :
>>  344       ZTask("ZFixupPartialLoadsTask"),
>>  345       _thread_roots() {}
>>  346
>>  347   virtual void work() {
>>  348     ZFixupPartialLoadsClosure cl;
>>  349     _thread_roots.oops_do(&cl);
>>  350   }
>>  351 };
>>  352
>>  353 void ZHeap::fixup_partial_loads() {
>>  354   ZFixupPartialLoadsTask task;
>>  355   _workers.run_parallel(&task);
>>  356 }
>>
>> cheers,
>> Per
>>
>>> Testing:
>>>
>>> Hotspot tier 1-6, CTW, jcstress, micros, runthese, kitchensink, and 
>>> then some. All with -XX:+ZVerifyViews.
>>>
>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8224675
>>>
>>> Webrev: http://cr.openjdk.java.net/~neliasso/8224675/webrev.01/
>>>
>>>
>>> Please review,
>>>
>>> Regards,
>>>
>>> Nils
>>>