Adjust pointer maps for branches when connecting live ranges.

Review URL: http://codereview.chromium.org/6541024

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6858 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

diff --git a/src/lithium-allocator.cc b/src/lithium-allocator.cc
index 9f5f1b9..0842940 100644 (file)
--- a/src/lithium-allocator.cc
+++ b/src/lithium-allocator.cc
@@ -1098,6 +1098,21 @@ void LAllocator::ResolveControlFlow(LiveRange* range,
       } else {
         ASSERT(pred->end()->SecondSuccessor() == NULL);
         gap = GetLastGap(pred);
+
+        // We are going to insert a move 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);
     }