Fix issue 982.

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 278 matching lines @@
 }
 
 
 void LiveRange::SplitAt(LifetimePosition position, LiveRange* result) {
   ASSERT(Start().Value() < position.Value());
   ASSERT(result->IsEmpty());
   // Find the last interval that ends before the position. If the
   // position is contained in one of the intervals in the chain, we
   // split that interval and use the first part.
   UseInterval* current = FirstSearchIntervalForPosition(position);
+
+  // If split position coincides with the beginning of use interval

[Kevin Millikin (Chromium), 2010/12/15 14:01:52]

"the split position"..."a use interval" :)

+  // we need to split use positons in a special way.
+  bool split_at_start = false;
+
   while (current != NULL) {
     if (current->Contains(position)) {
       current->SplitAt(position);
       break;
     }
     UseInterval* next = current->next();
-    if (next->start().Value() >= position.Value()) break;
+    if (next->start().Value() >= position.Value()) {
+      split_at_start = (next->start().Value() == position.Value());
+      break;
+    }
     current = next;
   }
 
   // Partition original use intervals to the two live ranges.
   UseInterval* before = current;
   UseInterval* after = before->next();
   result->last_interval_ = (last_interval_ == before)
       ? after            // Only interval in the range after split.
       : last_interval_;  // Last interval of the original range.
   result->first_interval_ = after;
   last_interval_ = before;
 
   // Find the last use position before the split and the first use
   // position after it.
   UsePosition* use_after = first_pos_;
   UsePosition* use_before = NULL;
-  while (use_after != NULL && use_after->pos().Value() <= position.Value()) {
-    use_before = use_after;
-    use_after = use_after->next();
+  if (split_at_start) {
+    while (use_after != NULL && use_after->pos().Value() < position.Value()) {

[Kevin Millikin (Chromium), 2010/12/15 14:01:52]

Maybe this case needs a short comment too, something like "We are splitting at
the start of an interval.  The use position at the start of the interval belongs
after the split."

+      use_before = use_after;
+      use_after = use_after->next();
+    }
+  } else {
+    while (use_after != NULL && use_after->pos().Value() <= position.Value()) {
+      use_before = use_after;
+      use_after = use_after->next();
+    }
   }
 
   // Partition original use positions to the two live ranges.
   if (use_before != NULL) {
     use_before->next_ = NULL;
   } else {
     first_pos_ = NULL;
   }
   result->first_pos_ = use_after;
 
@@ skipping 1759 matching lines @@
     LiveRange* current = live_ranges()->at(i);
     if (current != NULL) current->Verify();
   }
 }
 
 
 #endif
 
 
 } }  // namespace v8::internal