Add --check-code-pointer flag for debug builds

runtime/vm/assembler_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"  // NOLINT
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/assembler.h"
 #include "vm/cpu.h"
 #include "vm/heap.h"
 #include "vm/instructions.h"
 #include "vm/locations.h"
 #include "vm/memory_region.h"
 #include "vm/runtime_entry.h"
 #include "vm/stack_frame.h"
 #include "vm/stub_code.h"
 
 namespace dart {
 
 DECLARE_FLAG(bool, allow_absolute_addresses);
+DECLARE_FLAG(bool, check_code_pointer);
+DECLARE_FLAG(bool, inline_alloc);
+
 DEFINE_FLAG(bool, print_stop_message, true, "Print stop message.");
-DECLARE_FLAG(bool, inline_alloc);
 
 
 Assembler::Assembler(bool use_far_branches)
     : buffer_(),
       prologue_offset_(-1),
       comments_(),
       constant_pool_allowed_(false) {
   // Far branching mode is only needed and implemented for MIPS and ARM.
   ASSERT(!use_far_branches);
 }
@@ skipping 3307 matching lines @@
   CheckCodePointer();
   movq(pp, FieldAddress(CODE_REG, Code::object_pool_offset()));
   set_constant_pool_allowed(pp == PP);
 }
 
 
 void Assembler::EnterDartFrame(intptr_t frame_size, Register new_pp) {
   ASSERT(!constant_pool_allowed());
   EnterFrame(0);
   pushq(CODE_REG);
   pushq(PP);

[Florian Schneider, 2016/01/12 11:31:23]

Would it work to do CheckCodePointer here instead, after the Dart frame is
built? (and remove it from LoadPoolPointer)

   if (new_pp == kNoRegister) {
     LoadPoolPointer(PP);
   } else {
     movq(PP, new_pp);
   }
   set_constant_pool_allowed(true);
   if (frame_size != 0) {
     subq(RSP, Immediate(frame_size));
   }
 }
 
 
 void Assembler::LeaveDartFrame(RestorePP restore_pp) {
   // Restore caller's PP register that was pushed in EnterDartFrame.
   if (restore_pp == kRestoreCallerPP) {
     movq(PP, Address(RBP, (kSavedCallerPpSlotFromFp * kWordSize)));
     set_constant_pool_allowed(false);
   }
   LeaveFrame();
 }
 
 
 void Assembler::CheckCodePointer() {
 #ifdef DEBUG
+  if (!FLAG_check_code_pointer) {
+    return;
+  }
   Comment("CheckCodePointer");
   Label cid_ok, instructions_ok;
   pushq(RAX);
   LoadClassId(RAX, CODE_REG);
   cmpq(RAX, Immediate(kCodeCid));
   j(EQUAL, &cid_ok);
   int3();
   Bind(&cid_ok);
   {
     const intptr_t kRIPRelativeLeaqSize = 7;
@@ skipping 536 matching lines @@
 
 
 const char* Assembler::FpuRegisterName(FpuRegister reg) {
   ASSERT((0 <= reg) && (reg < kNumberOfXmmRegisters));
   return xmm_reg_names[reg];
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64