More aggressive reuse of spill slots in the register allocator.

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index 39554993d8c39144801849a0a1c83aa9ba046c73..f7b8e6a9c6b02b586958266322f762266be4be0a 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -11929,12 +11929,17 @@ void HTracer::TraceLiveRange(LiveRange* range, const char* type,
         trace_.Add(" \"%s\"", Register::AllocationIndexToString(assigned_reg));
       }
     } else if (range->IsSpilled()) {
-      LOperand* op = range->TopLevel()->GetSpillOperand();
-      if (op->IsDoubleStackSlot()) {
-        trace_.Add(" \"double_stack:%d\"", op->index());
+      int index = -1;
+      if (range->TopLevel()->GetSpillRangeId() != -1) {
+        index = range->TopLevel()->GetSpillRangeId();
       } else {
-        ASSERT(op->IsStackSlot());
-        trace_.Add(" \"stack:%d\"", op->index());
+        index = range->TopLevel()->GetSpillOperand()->index();
+      }
+      if (range->TopLevel()->Kind() == DOUBLE_REGISTERS) {
+        trace_.Add(" \"double_stack:%d\"", index);
+      } else {
+        ASSERT(range->TopLevel()->Kind() == GENERAL_REGISTERS);
+        trace_.Add(" \"stack:%d\"", index);
       }
     }
     int parent_index = -1;