VM: Fix bug in the new edge counter code on ARM and MIPS.

runtime/vm/flow_graph_compiler_arm.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"  // Needed here to get TARGET_ARCH_ARM.
 #if defined(TARGET_ARCH_ARM)
 
 #include "vm/flow_graph_compiler.h"
 
 #include "vm/ast_printer.h"
@@ skipping 1170 matching lines @@
 
 
 void FlowGraphCompiler::EmitEdgeCounter(intptr_t edge_id) {
   // We do not check for overflow when incrementing the edge counter.  The
   // function should normally be optimized long before the counter can
   // overflow; and though we do not reset the counters when we optimize or
   // deoptimize, there is a bound on the number of
   // optimization/deoptimization cycles we will attempt.
   ASSERT(!edge_counters_array_.IsNull());
   ASSERT(assembler_->constant_pool_allowed());
   const Array& counter = Array::ZoneHandle(zone(), Array::New(1, Heap::kOld));

[rmacnak, 2015/09/28 17:15:27]

Dead allocation.

[Florian Schneider, 2015/09/28 17:17:25]

Good catch. Done.

   counter.SetAt(0, Smi::Handle(zone(), Smi::New(0)));
   __ Comment("Edge counter");
   __ LoadObject(R0, edge_counters_array_);
 #if defined(DEBUG)
   bool old_use_far_branches = assembler_->use_far_branches();
   assembler_->set_use_far_branches(true);
 #endif  // DEBUG
-  __ ldr(IP, FieldAddress(R0, Array::element_offset(edge_id)));
-  __ add(IP, IP, Operand(Smi::RawValue(1)));
-  __ StoreIntoSmiField(FieldAddress(R0, Array::element_offset(edge_id)), IP);
+  __ LoadFieldFromOffset(kWord, R1, R0, Array::element_offset(edge_id));
+  __ add(R1, R1, Operand(Smi::RawValue(1)));
+  __ StoreIntoObjectNoBarrierOffset(
+      R0, Array::element_offset(edge_id), R1, Assembler::kOnlySmi);
 #if defined(DEBUG)
   assembler_->set_use_far_branches(old_use_far_branches);
 #endif  // DEBUG
 }
 
 
 void FlowGraphCompiler::EmitOptimizedInstanceCall(
     const StubEntry& stub_entry,
     const ICData& ic_data,
     intptr_t argument_count,
@@ skipping 653 matching lines @@
   DRegister dreg = EvenDRegisterOf(reg);
   __ vldrd(dreg, Address(SP, kDoubleSize, Address::PostIndex));
 }
 
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM