Add Uint32 representation

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/block_scheduler.h"
@@ skipping 435 matching lines @@
           // Propagate types after store-load-forwarding. Some phis may have
           // become smi phis that can be processed by range analysis.
           FlowGraphTypePropagator::Propagate(flow_graph);
           DEBUG_ASSERT(flow_graph->VerifyUseLists());
 
           // We have to perform range analysis after LICM because it
           // optimistically moves CheckSmi through phis into loop preheaders
           // making some phis smi.
           optimizer.InferIntRanges();
           DEBUG_ASSERT(flow_graph->VerifyUseLists());
+
+          // Select integer instructions based on range analysis result.
+          optimizer.SelectIntegerInstructions();

[Florian Schneider, 2014/07/08 12:24:28]

I think this phase should be run as part of RangeAnalysis by moving it to
RangeAnalysis::Analyze, so that the constraints inserted for branches are still
present.

[Cutch, 2014/07/09 17:48:25]

Are you suggesting that we do a range analysis pass *after* replacing Mint
operations with Uint32 operations? Please explain more what you're thinking.

[Florian Schneider, 2014/07/10 13:05:05]

No, your pass runs after range analysis, but before
RangeAnalysis::RemoveConstraints. This way you get better constraints for
branches. e.g.

if (a > 0 && a < 16) {
  // a has range [0..15] here.
}

[Cutch, 2014/07/10 17:12:53]

I've added a TODO for a follow up CL.

+          DEBUG_ASSERT(flow_graph->VerifyUseLists());
         }
 
         if (FLAG_constant_propagation) {
           // Constant propagation can use information from range analysis to
           // find unreachable branch targets and eliminate branches that have
           // the same true- and false-target.
           ConstantPropagator::OptimizeBranches(flow_graph);
           DEBUG_ASSERT(flow_graph->VerifyUseLists());
         }
 
@@ skipping 503 matching lines @@
     const Object& result =
       Object::Handle(isolate->object_store()->sticky_error());
     isolate->object_store()->clear_sticky_error();
     return result.raw();
   }
   UNREACHABLE();
   return Object::null();
 }
 
 }  // namespace dart