Fix bug LAllocator::FindOptimalSplitPos: it was calculating start_block and end_block incorrectly.

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 2011 matching lines @@
 
 LifetimePosition LAllocator::FindOptimalSplitPos(LifetimePosition start,
                                                  LifetimePosition end) {
   int start_instr = start.InstructionIndex();
   int end_instr = end.InstructionIndex();
   ASSERT(start_instr <= end_instr);
 
   // We have no choice
   if (start_instr == end_instr) return end;
 
-  HBasicBlock* end_block = GetBlock(start);
-  HBasicBlock* start_block = GetBlock(end);
+  HBasicBlock* start_block = GetBlock(start);
+  HBasicBlock* end_block = GetBlock(end);
 
   if (end_block == start_block) {
-    // The interval is split in the same basic block. Split at latest possible
-    // position.
+    // The interval is split in the same basic block. Split at the latest
+    // possible position.
     return end;
   }
 
   HBasicBlock* block = end_block;
   // Find header of outermost loop.
   while (block->parent_loop_header() != NULL &&
       block->parent_loop_header()->block_id() > start_block->block_id()) {
     block = block->parent_loop_header();
   }
 
-  if (block == end_block) return end;
+  // We did not find any suitable outer loop. Split at the latest possible
+  // position unless end_block is a loop header itself.
+  if (block == end_block && !end_block->IsLoopHeader()) return end;
 
   return LifetimePosition::FromInstructionIndex(
       block->first_instruction_index());
 }
 
 
 void LAllocator::SpillAfter(LiveRange* range, LifetimePosition pos) {
   LiveRange* second_part = SplitAt(range, pos);
   Spill(second_part);
 }
@@ skipping 53 matching lines @@
     LiveRange* current = live_ranges()->at(i);
     if (current != NULL) current->Verify();
   }
 }
 
 
 #endif
 
 
 } }  // namespace v8::internal