Support verified heap pointer writes on x64.

runtime/vm/code_patcher_x64.cc

 // Copyright (c) 2012, 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_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/assembler.h"
 #include "vm/code_patcher.h"
 #include "vm/cpu.h"
 #include "vm/dart_entry.h"
+#include "vm/flow_graph_compiler.h"
 #include "vm/instructions.h"
 #include "vm/object.h"
 #include "vm/raw_object.h"
 
 namespace dart {
 
 // The expected pattern of a Dart unoptimized call (static and instance):
 //  00: 49 8b 9f imm32  mov RBX, [PP + off]
 //  07: 4d 8b 9f imm32  mov R11, [PP + off]
 //  14: 41 ff d3        call R11
@@ skipping 274 matching lines @@
   }
   return ic_data.GetTargetAt(0);
 }
 
 
 // The expected code pattern of an edge counter in unoptimized code:
 //  49 8b 87 imm32    mov RAX, [PP + offset]
 class EdgeCounter : public ValueObject {
  public:
   EdgeCounter(uword pc, const Code& code)
-      : end_(pc - kAdjust), object_pool_(Array::Handle(code.ObjectPool())) {
+      : end_(pc - FlowGraphCompiler::EdgeCounterIncrementSizeInBytes()),
+        object_pool_(Array::Handle(code.ObjectPool())) {
     ASSERT(IsValid(end_));
   }
 
   static bool IsValid(uword end) {
     uint8_t* bytes = reinterpret_cast<uint8_t*>(end - 7);
     return (bytes[0] == 0x49) && (bytes[1] == 0x8b) && (bytes[2] == 0x87);
   }
 
   RawObject* edge_counter() const {
     return object_pool_.At(InstructionPattern::IndexFromPPLoad(end_ - 4));
   }
 
  private:
-  // The edge counter load is followed by the fixed-size edge counter
-  // incrementing code:
-  //     48 83 40 17 02             addq [rax+0x17],0x2
-  static const intptr_t kAdjust = 5;
-
   uword end_;
   const Array& object_pool_;
 };
 
 
 RawObject* CodePatcher::GetEdgeCounterAt(uword pc, const Code& code) {
   ASSERT(code.ContainsInstructionAt(pc));
   EdgeCounter counter(pc, code);
   return counter.edge_counter();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64