Canonicalize away redundant checks that appear after store-to-load forwarding.

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"
@@ skipping 228 matching lines @@
       }
 
       if (FLAG_range_analysis) {
         // We have to perform range analysis after LICM because it
         // optimistically moves CheckSmi through phis into loop preheaders
         // making some phis smi.
         flow_graph->ComputeUseLists();
         optimizer.InferSmiRanges();
       }
 
+      // The final canonicalization pass before the code generation.
+      optimizer.Canonicalize();
+
       // Perform register allocation on the SSA graph.
       FlowGraphAllocator allocator(*flow_graph);
       allocator.AllocateRegisters();
 
       if (FLAG_print_flow_graph || FLAG_print_flow_graph_optimized) {
         OS::Print("After Optimizations:\n");
         FlowGraphPrinter printer(*flow_graph);
         printer.PrintBlocks();
       }
     }
@@ skipping 378 matching lines @@
       Object::Handle(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