Maintain proper pointer map for branches when resolving phis.

src/lithium-allocator.cc

Index: src/lithium-allocator.cc
diff --git a/src/lithium-allocator.cc b/src/lithium-allocator.cc
index f62a7dbc0a2708fa879ff42a3a5f0063ab641972..0dd904a1bfea0263f89785cbdfc190f2a0b17639 100644
--- a/src/lithium-allocator.cc
+++ b/src/lithium-allocator.cc
@@ -1029,6 +1029,22 @@ void LAllocator::ResolvePhis(HBasicBlock* block) {
       chunk_->AddGapMove(cur_block->last_instruction_index() - 1,
                          operand,
                          phi_operand);
+
+      // 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

[fschneider, 2011/04/18 20:20:05]

->inserting

+      // 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 (phi->representation().IsTagged()) {
+        LInstruction* branch =
+            InstructionAt(cur_block->last_instruction_index());
+        if (branch->HasPointerMap()) {
+          branch->pointer_map()->RecordPointer(phi_operand);
+        }
+      }
     }
 
     LiveRange* live_range = LiveRangeFor(phi->id());