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

runtime/vm/flow_graph_allocator.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/flow_graph_allocator.h"
 
 #include "vm/bit_vector.h"
 #include "vm/intermediate_language.h"
 #include "vm/il_printer.h"
 #include "vm/flow_graph_builder.h"
@@ skipping 109 matching lines @@
 
     // Handle phis.
     if (block->IsJoinEntry()) {
       JoinEntryInstr* join = block->AsJoinEntry();
       if (join->phis() != NULL) {
         for (intptr_t j = 0; j < join->phis()->length(); j++) {
           PhiInstr* phi = (*join->phis())[j];
           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);
+              }
+            }
+          }
         }
       }
     }
   }
 
   // Process incoming parameters.
   GraphEntryInstr* graph_entry = postorder_[block_count - 1]->AsGraphEntry();
   for (intptr_t i = 0; i < graph_entry->start_env()->values().length(); i++) {
     Value* val = graph_entry->start_env()->values()[i];
     if (val->IsUse()) {
@@ skipping 1519 matching lines @@
 
   if (FLAG_trace_ssa_allocator) {
     OS::Print("-- ir after allocation -------------------------\n");
     FlowGraphPrinter printer(Function::Handle(), block_order_, true);
     printer.PrintBlocks();
   }
 }
 
 
 }  // namespace dart