8026293: Schedule part of G1 pre-barrier late

Summary: move rare executed part of G1 write barrier from hot path.
Reviewed-by: kvn, twisti, roland
Contributed-by: staffan.friberg@oracle.com

src/share/vm/opto/graphKit.cpp

@@ -3615,7 +3615,7 @@ void GraphKit::g1_write_barrier_pre(bool do_load,
   Node* marking = __ load(__ ctrl(), marking_adr, TypeInt::INT, active_type, Compile::AliasIdxRaw);
 
   // if (!marking)
-  __ if_then(marking, BoolTest::ne, zero); {
+  __ if_then(marking, BoolTest::ne, zero, unlikely); {
     BasicType index_bt = TypeX_X->basic_type();
     assert(sizeof(size_t) == type2aelembytes(index_bt), "Loading G1 PtrQueue::_index with wrong size.");
     Node* index   = __ load(__ ctrl(), index_adr, TypeX_X, index_bt, Compile::AliasIdxRaw);