ICData::NumberOfChecks is O(n) so don't call it in loops

runtime/vm/code_generator.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/code_generator.h"
 
 #include "vm/assembler.h"
 #include "vm/ast.h"
 #include "vm/code_patcher.h"
 #include "vm/compiler.h"
@@ skipping 920 matching lines @@
 
 
 // Handles a static call in unoptimized code that has one argument type not
 // seen before. Compile the target if necessary and update the ICData.
 // Arg0: argument.
 // Arg1: IC data object.
 DEFINE_RUNTIME_ENTRY(StaticCallMissHandlerOneArg, 2) {
   const Instance& arg = Instance::CheckedHandle(arguments.ArgAt(0));
   const ICData& ic_data = ICData::CheckedHandle(arguments.ArgAt(1));
   // IC data for static call is prepopulated with the statically known target.
-  ASSERT(ic_data.NumberOfChecks() == 1);
+  ASSERT(ic_data.NumberOfChecksIs(1));
   const Function& target = Function::Handle(ic_data.GetTargetAt(0));
   if (!target.HasCode()) {
     const Error& error =
         Error::Handle(Compiler::CompileFunction(thread, target));
     if (!error.IsNull()) {
       Exceptions::PropagateError(error);
     }
   }
   ASSERT(!target.IsNull() && target.HasCode());
   ic_data.AddReceiverCheck(arg.GetClassId(), target, 1);
@@ skipping 11 matching lines @@
 // Handles a static call in unoptimized code that has two argument types not
 // seen before. Compile the target if necessary and update the ICData.
 // Arg0: argument 0.
 // Arg1: argument 1.
 // Arg2: IC data object.
 DEFINE_RUNTIME_ENTRY(StaticCallMissHandlerTwoArgs, 3) {
   const Instance& arg0 = Instance::CheckedHandle(arguments.ArgAt(0));
   const Instance& arg1 = Instance::CheckedHandle(arguments.ArgAt(1));
   const ICData& ic_data = ICData::CheckedHandle(arguments.ArgAt(2));
   // IC data for static call is prepopulated with the statically known target.
-  ASSERT(ic_data.NumberOfChecks() > 0);
+  ASSERT(!ic_data.NumberOfChecksIs(0));
   const Function& target = Function::Handle(ic_data.GetTargetAt(0));
   if (!target.HasCode()) {
     const Error& error =
         Error::Handle(Compiler::CompileFunction(thread, target));
     if (!error.IsNull()) {
       Exceptions::PropagateError(error);
     }
   }
   ASSERT(!target.IsNull() && target.HasCode());
   GrowableArray<intptr_t> cids(2);
@@ skipping 319 matching lines @@
     target_function = InlineCacheMissHelper(receiver, descriptor, name);
   }
   if (target_function.IsNull()) {
     ASSERT(!FLAG_lazy_dispatchers);
     arguments.SetReturn(target_function);
     return;
   }
 
   if (ic_data_or_cache.IsICData()) {
     const ICData& ic_data = ICData::Cast(ic_data_or_cache);
+    const intptr_t number_of_checks = ic_data.NumberOfChecks();
 
-    if ((ic_data.NumberOfChecks() == 0) &&
-        !target_function.HasOptionalParameters() &&
+    if (number_of_checks == 0 && !target_function.HasOptionalParameters() &&
         !Isolate::Current()->compilation_allowed()) {
       // This call site is unlinked: transition to a monomorphic direct call.
       // Note we cannot do this if the target has optional parameters because
       // the monomorphic direct call does not load the arguments descriptor.
       // We cannot do this if we are still in the middle of precompiling because
       // the monomorphic case hides an live instance selector from the
       // treeshaker.
 
       if (!target_function.HasCode()) {
         const Error& error =
@@ skipping 12 matching lines @@
           Code::Handle(zone, caller_frame->LookupDartCode());
       const Code& target_code =
           Code::Handle(zone, target_function.CurrentCode());
       const Smi& expected_cid =
           Smi::Handle(zone, Smi::New(receiver.GetClassId()));
 
       CodePatcher::PatchSwitchableCallAt(caller_frame->pc(), caller_code,
                                          expected_cid, target_code);
     } else {
       ic_data.AddReceiverCheck(receiver.GetClassId(), target_function);
-      if (ic_data.NumberOfChecks() > FLAG_max_polymorphic_checks) {
+      if (number_of_checks > FLAG_max_polymorphic_checks) {
         // Switch to megamorphic call.
         const MegamorphicCache& cache = MegamorphicCache::Handle(
             zone, MegamorphicCacheTable::Lookup(isolate, name, descriptor));
         DartFrameIterator iterator;
         StackFrame* miss_function_frame = iterator.NextFrame();
         ASSERT(miss_function_frame->IsDartFrame());
         StackFrame* caller_frame = iterator.NextFrame();
         ASSERT(caller_frame->IsDartFrame());
         const Code& caller_code =
             Code::Handle(zone, caller_frame->LookupDartCode());
@@ skipping 902 matching lines @@
   const intptr_t elm_size = old_data.ElementSizeInBytes();
   const TypedData& new_data =
       TypedData::Handle(TypedData::New(cid, new_size, Heap::kOld));
   TypedData::Copy(new_data, 0, old_data, 0, old_size * elm_size);
   typed_data_cell.SetAt(0, new_data);
   arguments.SetReturn(new_data);
 }
 
 
 }  // namespace dart