Support Int32 representation for selected binary operations.

runtime/vm/compiler.cc

Index: runtime/vm/compiler.cc
diff --git a/runtime/vm/compiler.cc b/runtime/vm/compiler.cc
index 81ba5f3f1b18ee132c9ec68bf4a7d594c9c1765a..b78f0c721e3f150f1886e345fd73a9ffdd25ff08 100644
--- a/runtime/vm/compiler.cc
+++ b/runtime/vm/compiler.cc
@@ -411,12 +411,24 @@ static bool CompileParsedFunctionHelper(ParsedFunction* parsed_function,
           DEBUG_ASSERT(flow_graph->VerifyUseLists());
         }
 
+        // Optimistically convert loop phis that have a single non-smi input
+        // coming from the loop pre-header into smi-phis.
+        if (FLAG_loop_invariant_code_motion) {
+          LICM licm(flow_graph);
+          licm.OptimisticallySpecializeSmiPhis();
+          DEBUG_ASSERT(flow_graph->VerifyUseLists());
+        }
+
         // Propagate types and eliminate even more type tests.
         // Recompute types after constant propagation to infer more precise
         // types for uses that were previously reached by now eliminated phis.
         FlowGraphTypePropagator::Propagate(flow_graph);
         DEBUG_ASSERT(flow_graph->VerifyUseLists());
 
+        // Where beneficial convert Smi operations into Int32 operations.
+        // Only meanigful for 32bit platforms right now.
+        optimizer.WidenSmiToInt32();
+
         // Unbox doubles. Performed after constant propagation to minimize
         // interference from phis merging double values and tagged
         // values coming from dead paths.