Implement range analysis for smi values.

runtime/vm/compiler.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/compiler.h"
 
 #include "vm/assembler.h"
 #include "vm/ast_printer.h"
 #include "vm/code_generator.h"
 #include "vm/code_patcher.h"
@@ skipping 187 matching lines @@
 
         // Unbox doubles.
         flow_graph->ComputeUseLists();
         optimizer.SelectRepresentations();
 
         if (FLAG_cp || FLAG_cse) flow_graph->ComputeUseLists();
         if (FLAG_cp) ConstantPropagator::Optimize(flow_graph);
         if (FLAG_cse) DominatorBasedCSE::Optimize(flow_graph);
         if (FLAG_licm) LICM::Optimize(flow_graph);
 
+        // We have to perform range analysis after LICM because it
+        // optimistically moves CheckSmi through phis into loop preheaders
+        // making some phis smi.

[ngeoffray, 2012/09/24 21:44:15]

The first part of the sentence makes you think it's a requirement, but the
second part makes you think it's actually just an optimization.

+        flow_graph->ComputeUseLists();
+        optimizer.InferSmiRanges();
+
         // Perform register allocation on the SSA graph.
         FlowGraphAllocator allocator(*flow_graph);
         allocator.AllocateRegisters();
 
         if (FLAG_print_flow_graph) {
           OS::Print("After Optimizations:\n");
           FlowGraphPrinter printer(*flow_graph);
           printer.PrintBlocks();
         }
       }
@@ skipping 344 matching lines @@
     result = isolate->object_store()->sticky_error();
     isolate->object_store()->clear_sticky_error();
     isolate->set_long_jump_base(base);
     return result.raw();
   }
   UNREACHABLE();
   return Object::null();
 }
 
 }  // namespace dart