VM: Improve polymorphic check-class in optimized code.

runtime/vm/intermediate_language_arm.cc

Index: runtime/vm/intermediate_language_arm.cc
===================================================================
--- runtime/vm/intermediate_language_arm.cc	(revision 43352)
+++ runtime/vm/intermediate_language_arm.cc	(working copy)
@@ -6029,11 +6029,9 @@
   const Register value = locs()->in(0).reg();
   const Register temp = locs()->temp(0).reg();
   Label is_ok;
-  intptr_t cix = 0;
-  if (unary_checks().GetReceiverClassIdAt(cix) == kSmiCid) {
+  if (unary_checks().GetReceiverClassIdAt(0) == kSmiCid) {
     __ tst(value, Operand(kSmiTagMask));
     __ b(&is_ok, EQ);
-    cix++;  // Skip first check.
   } else {
     __ tst(value, Operand(kSmiTagMask));
     __ b(deopt, EQ);
@@ -6057,10 +6055,15 @@
       __ b(deopt, EQ);
     }
   } else {
-    const intptr_t num_checks = unary_checks().NumberOfChecks();
-    for (intptr_t i = cix; i < num_checks; i++) {
-      ASSERT(unary_checks().GetReceiverClassIdAt(i) != kSmiCid);
-      __ CompareImmediate(temp, unary_checks().GetReceiverClassIdAt(i));
+    GrowableArray<CidTarget> sorted_ic_data;
+    FlowGraphCompiler::SortICDataByCount(unary_checks(),
+                                         &sorted_ic_data,
+                                         /* drop_smi = */ true);
+    const intptr_t num_checks = sorted_ic_data.length();
+    for (intptr_t i = 0; i < num_checks; i++) {
+      const intptr_t cid = sorted_ic_data[i].cid;
+      ASSERT(cid != kSmiCid);
+      __ CompareImmediate(temp, cid);
       if (i == (num_checks - 1)) {
         __ b(deopt, NE);
       } else {