Fix bug in register allocation at catch entry blocks.

runtime/vm/flow_graph_allocator.cc

Index: runtime/vm/flow_graph_allocator.cc
===================================================================
--- runtime/vm/flow_graph_allocator.cc	(revision 24096)
+++ runtime/vm/flow_graph_allocator.cc	(working copy)
@@ -60,6 +60,12 @@
 }
 
 
+static intptr_t NextInstructionPos(intptr_t pos) {
+  ASSERT(IsInstructionStartPosition(pos));
+  return pos + 2;
+}
+
+
 FlowGraphAllocator::FlowGraphAllocator(const FlowGraph& flow_graph)
   : flow_graph_(flow_graph),
     reaching_defs_(flow_graph),
@@ -512,6 +518,15 @@
         range->DefineAt(catch_entry->start_pos());  // Defined at block entry.
         ProcessInitialDefinition(defn, range, catch_entry);
       }
+      // Block the two registers used by CatchEntryInstr from the block start to
+      // until the end of the instruction so that they are preserved.
+      intptr_t start = catch_entry->start_pos();
+      BlockLocation(Location::RegisterLocation(kExceptionObjectReg),
+                    start,
+                    ToInstructionEnd(NextInstructionPos(start)));
+      BlockLocation(Location::RegisterLocation(kStackTraceObjectReg),
+                    start,
+                    ToInstructionEnd(NextInstructionPos(start)));

[Vyacheslav Egorov (Google), 2013/06/17 15:11:39]

Assert that the next instruction is actually CatchEntryInstr

[Florian Schneider, 2013/06/17 17:35:35]

Done.

     }
   }