Make constant propagation to fold x == x and re-run type propagation for better range analysis.

runtime/vm/compiler.cc

Index: runtime/vm/compiler.cc
===================================================================
--- runtime/vm/compiler.cc	(revision 23898)
+++ runtime/vm/compiler.cc	(working copy)
@@ -406,6 +406,13 @@
       flow_graph->RemoveRedefinitions();
 
       if (FLAG_range_analysis) {
+        if (FLAG_propagate_types) {
+          // Propagate types after store-load-forwarding. Some phis may have
+          // become smi phis that can be processed by range analysis.
+          FlowGraphTypePropagator propagator(flow_graph);
+          propagator.Propagate();
+          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.
@@ -420,7 +427,6 @@
         DEBUG_ASSERT(flow_graph->VerifyUseLists());
       }
 
-      // The final canonicalization pass before the code generation.
       if (FLAG_propagate_types) {
         // Recompute types after code movement was done to ensure correct
         // reaching types for hoisted values.
@@ -447,7 +453,7 @@
 
       // Ensure that all phis inserted by optimization passes have consistent
       // representations.
-      optimizer.UnboxPhis();
+      optimizer.SelectRepresentations();
 
       if (optimizer.Canonicalize()) {
         // To fully remove redundant boxing (e.g. BoxDouble used only in