Fix a register allocation crash on IA32, caused by an uninitialized finger.

runtime/vm/flow_graph_allocator.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/flow_graph_allocator.h"
 
 #include "vm/bit_vector.h"
 #include "vm/intermediate_language.h"
 #include "vm/il_printer.h"
 #include "vm/flow_graph_builder.h"
@@ skipping 1046 matching lines @@
 LiveRange* LiveRange::MakeTemp(intptr_t pos, Location* location_slot) {
   UNREACHABLE();
   return NULL;
 }
 
 
 LiveRange* LiveRange::SplitAt(intptr_t split_pos) {
   if (Start() == split_pos) return this;
 
   UseInterval* interval = finger_.first_pending_use_interval();
+  if (interval == NULL) {

[Vyacheslav Egorov (Google), 2012/08/02 13:38:56]

We should consider initializing finger eagerly.

+    finger_.Initialize(this);
+    interval = finger_.first_pending_use_interval();
+  }
+
   ASSERT(interval->start() < split_pos);
   ASSERT(split_pos < End());
 
   // Corner case. We need to start over to find previous interval.
   if (interval->start() == split_pos) interval = first_use_interval_;
 
   UseInterval* last_before_split = NULL;
   while (interval->end() <= split_pos) {
     last_before_split = interval;
     interval = interval->next();
@@ skipping 672 matching lines @@
     OS::Print("-- [after ssa allocator] ir [%s] -------------\n",
               function.ToFullyQualifiedCString());
     FlowGraphPrinter printer(Function::Handle(), block_order_, true);
     printer.PrintBlocks();
     OS::Print("----------------------------------------------\n");
   }
 }
 
 
 }  // namespace dart