Adjust pointer maps for branches when connecting live ranges.

src/lithium-allocator.cc

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1080 matching lines @@
   if (pred_cover != cur_cover) {
     LOperand* pred_op = pred_cover->CreateAssignedOperand();
     LOperand* cur_op = cur_cover->CreateAssignedOperand();
     if (!pred_op->Equals(cur_op)) {
       LGap* gap = NULL;
       if (block->predecessors()->length() == 1) {
         gap = GapAt(block->first_instruction_index());
       } else {
         ASSERT(pred->end()->SecondSuccessor() == NULL);
         gap = GetLastGap(pred);
+
+        // We are going to insert mov from one live-range to another before the
+        // branch instruction. Some branch instructions (e.g. loops' back edges)
+        // can potentially cause a GC so they have a pointer map.
+        // By insterting a move we essentially create a copy of a
+        // value which is invisible to PopulatePointerMaps(), because we store
+        // it into a location different from the operand of a live range
+        // covering a branch instruction.
+        // Thus we need to manually record a pointer.
+        if (HasTaggedValue(range->id())) {
+          LInstruction* branch = InstructionAt(pred->last_instruction_index());
+          if (branch->HasPointerMap()) {
+            branch->pointer_map()->RecordPointer(cur_op);
+          }
+        }
       }
       gap->GetOrCreateParallelMove(LGap::START)->AddMove(pred_op, cur_op);
     }
   }
 }
 
 
 LParallelMove* LAllocator::GetConnectingParallelMove(LifetimePosition pos) {
   int index = pos.InstructionIndex();
   if (IsGapAt(index)) {
@@ skipping 963 matching lines @@
     LiveRange* current = live_ranges()->at(i);
     if (current != NULL) current->Verify();
   }
 }
 
 
 #endif
 
 
 } }  // namespace v8::internal