Fix bug in register allocation at catch entry blocks.

runtime/vm/flow_graph_allocator.cc

 // Copyright (c) 2013, 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.h"
@@ skipping 42 matching lines @@
 static intptr_t ToInstructionStart(intptr_t pos) {
   return (pos & ~1);
 }
 
 
 static intptr_t ToInstructionEnd(intptr_t pos) {
   return (pos | 1);
 }
 
 
+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),
     value_representations_(flow_graph.max_virtual_register_number()),
     block_order_(flow_graph.reverse_postorder()),
     postorder_(flow_graph.postorder()),
     liveness_(flow_graph),
     vreg_count_(flow_graph.max_virtual_register_number()),
     live_ranges_(flow_graph.max_virtual_register_number()),
     cpu_regs_(),
@@ skipping 432 matching lines @@
       // Process initial definitions.
       CatchBlockEntryInstr* catch_entry = block->AsCatchBlockEntry();
       for (intptr_t i = 0;
            i < catch_entry->initial_definitions()->length();
            i++) {
         Definition* defn = (*catch_entry->initial_definitions())[i];
         LiveRange* range = GetLiveRange(defn->ssa_temp_index());
         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.

     }
   }
 
   // Process incoming parameters and constants.  Do this after all other
   // instructions so that safepoints for all calls have already been found.
   GraphEntryInstr* graph_entry = flow_graph_.graph_entry();
   for (intptr_t i = 0; i < graph_entry->initial_definitions()->length(); i++) {
     Definition* defn = (*graph_entry->initial_definitions())[i];
     LiveRange* range = GetLiveRange(defn->ssa_temp_index());
     range->AddUseInterval(graph_entry->start_pos(), graph_entry->end_pos());
@@ skipping 2060 matching lines @@
     OS::Print("-- [after ssa allocator] ir [%s] -------------\n",
               function.ToFullyQualifiedCString());
     FlowGraphPrinter printer(flow_graph_, true);
     printer.PrintBlocks();
     OS::Print("----------------------------------------------\n");
   }
 }
 
 
 }  // namespace dart