8320907: Shenandoah: Remove ShenandoahSelfFixing flag

Backport-of: 43c7f6a673c2fa0b4dbec232e92b621619a98246

Author: shipilev

src/hotspot/share/gc/shenandoah/c2/shenandoahSupport.cpp

@@ -1386,11 +1386,9 @@ void ShenandoahBarrierC2Support::pin_and_expand(PhaseIdealLoop* phase) {
     Node* result_mem = nullptr;
 
     Node* addr;
-    if (ShenandoahSelfFixing) {
+    {
       VectorSet visited;
       addr = get_load_addr(phase, visited, lrb);
-    } else {
-      addr = phase->igvn().zerocon(T_OBJECT);
     }
     if (addr->Opcode() == Op_AddP) {
       Node* orig_base = addr->in(AddPNode::Base);

src/hotspot/share/gc/shenandoah/shenandoahBarrierSet.inline.hpp

@@ -123,7 +123,7 @@ inline oop ShenandoahBarrierSet::load_reference_barrier(DecoratorSet decorators,
   }
 
   oop fwd = load_reference_barrier(obj);
-  if (ShenandoahSelfFixing && load_addr != nullptr && fwd != obj) {
+  if (load_addr != nullptr && fwd != obj) {
     // Since we are here and we know the load address, update the reference.
     ShenandoahHeap::atomic_update_oop(fwd, load_addr, obj);
   }

src/hotspot/share/gc/shenandoah/shenandoah_globals.hpp

@@ -361,9 +361,6 @@
   product(bool, ShenandoahLoopOptsAfterExpansion, true, DIAGNOSTIC,         \
           "Attempt more loop opts after barrier expansion.")                \
                                                                             \
-  product(bool, ShenandoahSelfFixing, true, DIAGNOSTIC,                     \
-          "Fix references with load reference barrier. Disabling this "     \
-          "might degrade performance.")
 
 // end of GC_SHENANDOAH_FLAGS