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 14ef417636405203e257387e64e59138f7776357..5b2982b2a1491bbba7cc3109071664149ada217e 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -12359,12 +12359,17 @@ 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()->GetSpillRange()->id() != -1) {
+        index = range->TopLevel()->GetSpillRange()->id();
       } else {
-        DCHECK(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 {
+        DCHECK(range->TopLevel()->Kind() == GENERAL_REGISTERS);
+        trace_.Add(" \"stack:%d\"", index);
       }
     }
     int parent_index = -1;