VM-codegen: For polymorphic methods don't expand Cids at call sites

runtime/vm/intermediate_language.cc

 // Copyright (c) 2013, 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/intermediate_language.h"
 
 #include "vm/bit_vector.h"
 #include "vm/bootstrap.h"
 #include "vm/compiler.h"
 #include "vm/constant_propagator.h"
@@ skipping 2927 matching lines @@
 
   Array& args_desc_array = Array::Handle(zone, ic_data.arguments_descriptor());
   ArgumentsDescriptor args_desc(args_desc_array);
   String& name = String::Handle(zone, ic_data.target_name());
 
   Function& fn = Function::Handle(zone);
 
   intptr_t length = targets.length();
 
   // Spread class-ids to preceding classes where a lookup yields the same
-  // method.
+  // method.  A polymorphic target is not really the same method since its
+  // behaviour depends on the receiver class-id, so we don't spread the
+  // class-ids in that case.
   for (int idx = 0; idx < length; idx++) {
     int lower_limit_cid = (idx == 0) ? -1 : targets[idx - 1].cid_end;
     const Function& target = *targets.TargetAt(idx)->target;
+    if (MethodRecognizer::PolymorphicTarget(target)) continue;
     for (int i = targets[idx].cid_start - 1; i > lower_limit_cid; i--) {
       if (FlowGraphCompiler::LookupMethodFor(i, name, args_desc, &fn) &&
           fn.raw() == target.raw()) {
         targets[idx].cid_start = i;
       } else {
         break;
       }
     }
   }
   // Spread class-ids to following classes where a lookup yields the same
   // method.
   for (int idx = 0; idx < length; idx++) {
     int upper_limit_cid =
         (idx == length - 1) ? 1000000000 : targets[idx + 1].cid_start;
     const Function& target = *targets.TargetAt(idx)->target;
+    if (MethodRecognizer::PolymorphicTarget(target)) continue;
     for (int i = targets[idx].cid_end + 1; i < upper_limit_cid; i++) {
       if (FlowGraphCompiler::LookupMethodFor(i, name, args_desc, &fn) &&
           fn.raw() == target.raw()) {
         targets[idx].cid_end = i;
       } else {
         break;
       }
     }
   }
   targets.MergeIntoRanges();
   return &targets;
 }
 
 
 void CallTargets::MergeIntoRanges() {
   // Merge adjacent class id ranges.
   int dest = 0;
+  // We merge entries that dispatch to the same target, but polymorphic targets
+  // are not really the same target since they depend on the class-id, so we
+  // don't merge them.
   for (int src = 1; src < length(); src++) {
+    const Function& target = *TargetAt(dest)->target;
     if (TargetAt(dest)->cid_end + 1 >= TargetAt(src)->cid_start &&
-        TargetAt(dest)->target->raw() == TargetAt(src)->target->raw()) {
+        target.raw() == TargetAt(src)->target->raw() &&
+        !MethodRecognizer::PolymorphicTarget(target)) {
       TargetAt(dest)->cid_end = TargetAt(src)->cid_end;
       TargetAt(dest)->count += TargetAt(src)->count;
     } else {
       dest++;
       if (src != dest) {
         // Use cid_ranges_ instead of TargetAt when updating the pointer.
         cid_ranges_[dest] = TargetAt(src);
       }
     }
   }
@@ skipping 1362 matching lines @@
                      "native function '%s' (%" Pd " arguments) cannot be found",
                      native_name().ToCString(), function().NumParameters());
   }
   set_is_auto_scope(auto_setup_scope);
   set_native_c_function(native_function);
 }
 
 #undef __
 
 }  // namespace dart