Mark phi-operands live-in for a predecessor if they are not defined by it.

runtime/vm/flow_graph_allocator.cc

Index: runtime/vm/flow_graph_allocator.cc
diff --git a/runtime/vm/flow_graph_allocator.cc b/runtime/vm/flow_graph_allocator.cc
index 0b5998270b467542e4f806d47a111637419b14da..73cda77f58748d43ae337014b161f4c1a4da1674 100644
--- a/runtime/vm/flow_graph_allocator.cc
+++ b/runtime/vm/flow_graph_allocator.cc
@@ -127,6 +127,19 @@ void FlowGraphAllocator::ComputeInitialSets() {
           if (phi == NULL) continue;
           kill->Add(phi->ssa_temp_index());
           live_in->Remove(phi->ssa_temp_index());
+
+          // If phi-operand is not defined by a predecessor it must be marked
+          // live-in for a predecessor.
+          for (intptr_t k = 0; k < phi->InputCount(); k++) {
+            Value* val = phi->InputAt(k);
+            if (val->IsUse()) {
+              BlockEntryInstr* pred = block->PredecessorAt(k);
+              const intptr_t use = val->AsUse()->definition()->ssa_temp_index();
+              if (!kill_[pred->postorder_number()]->Contains(use)) {
+                live_in_[pred->postorder_number()]->Add(use);
+              }
+            }
+          }
         }
       }
     }