Uses a conditional move for usage counter increment instead of a branch

runtime/vm/stub_code_x64.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/globals.h"
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/assembler.h"
 #include "vm/compiler.h"
 #include "vm/dart_entry.h"
@@ skipping 1352 matching lines @@
   __ popq(R10);  // Restore arguments descriptor array.
   __ LeaveStubFrame();
   Label call_target_function;
   __ jmp(&call_target_function);
 
   __ Bind(&found);
   // R12: Pointer to an IC data check group.
   const intptr_t target_offset = ICData::TargetIndexFor(num_args) * kWordSize;
   const intptr_t count_offset = ICData::CountIndexFor(num_args) * kWordSize;
   __ movq(RAX, Address(R12, target_offset));
-  __ addq(Address(R12, count_offset), Immediate(Smi::RawValue(1)));
-  __ j(NO_OVERFLOW, &call_target_function, Assembler::kNearJump);
-  __ movq(Address(R12, count_offset),
-          Immediate(Smi::RawValue(Smi::kMaxValue)));
+
+  // Update counter.
+  __ movq(R8, Address(R12, count_offset));
+  __ addq(R8, Immediate(Smi::RawValue(1)));
+  __ movq(R9, Immediate(Smi::RawValue(Smi::kMaxValue)));
+  __ cmovnoq(R9, R8);
+  __ movq(Address(R12, count_offset), R9);

[srdjan, 2014/07/10 17:07:36]

ditto

[zra, 2014/07/10 17:15:40]

See link.

 
   __ Bind(&call_target_function);
   // RAX: Target function.
   Label is_compiled;
   __ movq(RCX, FieldAddress(RAX, Function::instructions_offset()));
   __ addq(RCX, Immediate(Instructions::HeaderSize() - kHeapObjectTag));
   __ jmp(RCX);
 }
 
 
@@ skipping 473 matching lines @@
 
   __ movq(left, Address(RSP, 2 * kWordSize));
   __ movq(right, Address(RSP, 1 * kWordSize));
   GenerateIdenticalWithNumberCheckStub(assembler, left, right);
   __ ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64