Really really fix mac x64 debug build by using more fixed-length encoding and long jumps.

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"
@@ skipping 3041 matching lines @@
 
 #if defined(DEBUG)
 void Assembler::VerifyObjectOrSmi(const Address& dest) {
   Label ok;
   testb(dest, Immediate(kHeapObjectTag));
   j(ZERO, &ok, Assembler::kNearJump);
   // Non-smi case: Verify object pointer is word-aligned when untagged.
   COMPILE_ASSERT(kHeapObjectTag == 1);
   testb(dest, Immediate((kWordSize - 1) - kHeapObjectTag));
   j(ZERO, &ok, Assembler::kNearJump);
-  Stop("Expected heap object or Smi");
+  static const bool kFixedLengthEncoding = true;

[Florian Schneider, 2015/01/12 10:31:51]

It does not matter here, but I think we tend not to use static linkage for local
variables. There isn't any benefit here either, so I'd just drop static for this
local.

+  Stop("Expected heap object or Smi", kFixedLengthEncoding);
   Bind(&ok);
 }
 
 
 void Assembler::VerifyUninitialized(const Address& dest) {
   Label ok;
   testb(dest, Immediate(kHeapObjectTag));
   j(ZERO, &ok, Assembler::kNearJump);
   // Non-smi case: Check for the special zap word or null.
 #if defined(DEBUG)
   cmpq(dest, Immediate(Heap::kZap64Bits));
   j(EQUAL, &ok, Assembler::kNearJump);
 #else
 #error Only supported in DEBUG mode
 #endif
   cmpq(dest, Immediate(reinterpret_cast<uint64_t>(Object::null())));
   j(EQUAL, &ok, Assembler::kNearJump);
-  Stop("Expected zapped, Smi or null");
+  static const bool kFixedLengthEncoding = true;

[Florian Schneider, 2015/01/12 10:31:51]

Same.

+  Stop("Expected zapped, Smi or null", kFixedLengthEncoding);
   Bind(&ok);
 }
 
 
 void Assembler::VerifySmi(const Address& dest, const char* stop_msg) {
   Label done;
   testb(dest, Immediate(kHeapObjectTag));
   j(ZERO, &done, Assembler::kNearJump);
   static const bool kFixedLengthEncoding = true;
   Stop(stop_msg, kFixedLengthEncoding);
@@ skipping 909 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