Optimize branches in polymorphic equality operations.

runtime/vm/intermediate_language_ia32.cc

Index: runtime/vm/intermediate_language_ia32.cc
===================================================================
--- runtime/vm/intermediate_language_ia32.cc	(revision 18211)
+++ runtime/vm/intermediate_language_ia32.cc	(working copy)
@@ -462,7 +462,11 @@
     ASSERT((ic_data.GetReceiverClassIdAt(i) != kSmiCid) || (i == 0));
     Label next_test;
     __ cmpl(temp, Immediate(ic_data.GetReceiverClassIdAt(i)));
-    __ j(NOT_EQUAL, &next_test);
+    if (i < len - 1) {
+      __ j(NOT_EQUAL, &next_test);
+    } else {
+      __ j(NOT_EQUAL, deopt);
+    }
     const Function& target = Function::ZoneHandle(ic_data.GetTargetAt(i));
     if (target.Owner() == object_store->object_class()) {
       // Object.== is same as ===.
@@ -497,7 +501,6 @@
           __ jmp(&done);
           __ Bind(&false_label);
           __ LoadObject(EAX, Bool::False());
-          __ jmp(&done);
         }
       } else {
         if (branch->is_checked()) {
@@ -507,11 +510,11 @@
         branch->EmitBranchOnCondition(compiler, cond);
       }
     }
-    __ jmp(&done);
+    if (i < len - 1) {
+      __ jmp(&done);
+    }
     __ Bind(&next_test);

[Kevin Millikin (Google), 2013/02/08 14:21:29]

This can go inside the if, no?  That might be clearer.

[Florian Schneider, 2013/02/08 15:30:28]

Yes, it can. Done.

   }
-  // Fall through leads to deoptimization
-  __ jmp(deopt);
   __ Bind(&done);
 }