8256481: [lworld] C2 fails to eliminate GC barriers when replacing inline type buffer allocation

Author: TobiHartmann

src/hotspot/share/gc/g1/c2/g1BarrierSetC2.cpp

@@ -698,24 +698,22 @@ void G1BarrierSetC2::eliminate_gc_barrier(PhaseIterGVN* igvn, Node* node) const
     // There is no G1 pre barrier if previous stored value is NULL
     // (for example, after initialization).
     if (this_region->is_Region() && this_region->req() == 3) {
-      int ind = 1;
-      if (!this_region->in(ind)->is_IfFalse()) {
-        ind = 2;
-      }
-      if (this_region->in(ind)->is_IfFalse() &&
-          this_region->in(ind)->in(0)->Opcode() == Op_If) {
-        Node* bol = this_region->in(ind)->in(0)->in(1);
-        assert(bol->is_Bool(), "");
-        cmpx = bol->in(1);
-        if (bol->as_Bool()->_test._test == BoolTest::ne &&
-            cmpx->is_Cmp() && cmpx->in(2) == igvn->intcon(0) &&
-            cmpx->in(1)->is_Load()) {
-          Node* adr = cmpx->in(1)->as_Load()->in(MemNode::Address);
-          const int marking_offset = in_bytes(G1ThreadLocalData::satb_mark_queue_active_offset());
-          if (adr->is_AddP() && adr->in(AddPNode::Base) == igvn->C->top() &&
-              adr->in(AddPNode::Address)->Opcode() == Op_ThreadLocal &&
-              adr->in(AddPNode::Offset) == igvn->MakeConX(marking_offset)) {
-            igvn->replace_node(cmpx, igvn->makecon(TypeInt::CC_EQ));
+      for (int i = 1; i < 3; ++i) {
+        if (this_region->in(i)->is_IfFalse() &&
+            this_region->in(i)->in(0)->is_If() &&
+            this_region->in(i)->in(0)->in(1)->is_Bool()) {
+          Node* bol = this_region->in(i)->in(0)->in(1);
+          cmpx = bol->in(1);
+          if (bol->as_Bool()->_test._test == BoolTest::ne &&
+              cmpx->is_Cmp() && cmpx->in(2) == igvn->intcon(0) &&
+              cmpx->in(1)->is_Load()) {
+            Node* adr = cmpx->in(1)->as_Load()->in(MemNode::Address);
+            const int marking_offset = in_bytes(G1ThreadLocalData::satb_mark_queue_active_offset());
+            if (adr->is_AddP() && adr->in(AddPNode::Base) == igvn->C->top() &&
+                adr->in(AddPNode::Address)->Opcode() == Op_ThreadLocal &&
+                adr->in(AddPNode::Offset) == igvn->MakeConX(marking_offset)) {
+              igvn->replace_node(cmpx, igvn->makecon(TypeInt::CC_EQ));
+            }
           }
         }
       }

src/hotspot/share/gc/shared/c2/cardTableBarrierSetC2.cpp

@@ -170,19 +170,23 @@ bool CardTableBarrierSetC2::is_gc_barrier_node(Node* node) const {
 
 void CardTableBarrierSetC2::eliminate_gc_barrier(PhaseIterGVN* igvn, Node* node) const {
   assert(node->Opcode() == Op_CastP2X, "ConvP2XNode required");
-  Node *shift = node->unique_out();
-  Node *addp = shift->unique_out();
-  for (DUIterator_Last jmin, j = addp->last_outs(jmin); j >= jmin; --j) {
-    Node *mem = addp->last_out(j);
-    if (UseCondCardMark && mem->is_Load()) {
-      assert(mem->Opcode() == Op_LoadB, "unexpected code shape");
-      // The load is checking if the card has been written so
-      // replace it with zero to fold the test.
-      igvn->replace_node(mem, igvn->intcon(0));
-      continue;
+  for (DUIterator_Last imin, i = node->last_outs(imin); i >= imin; --i) {
+    Node* shift = node->last_out(i);
+    for (DUIterator_Last jmin, j = shift->last_outs(jmin); j >= jmin; --j) {
+      Node* addp = shift->last_out(j);
+      for (DUIterator_Last kmin, k = addp->last_outs(kmin); k >= kmin; --k) {
+        Node* mem = addp->last_out(k);
+        if (UseCondCardMark && mem->is_Load()) {
+          assert(mem->Opcode() == Op_LoadB, "unexpected code shape");
+          // The load is checking if the card has been written so
+          // replace it with zero to fold the test.
+          igvn->replace_node(mem, igvn->intcon(0));
+          continue;
+        }
+        assert(mem->is_Store(), "store required");
+        igvn->replace_node(mem, mem->in(MemNode::Memory));
+      }
     }
-    assert(mem->is_Store(), "store required");
-    igvn->replace_node(mem, mem->in(MemNode::Memory));
   }
 }