Follow-up fix to my change to IsPowerOfTwo: Alignment of one means no alignment, not zero.

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"
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/assembler.h"
 #include "vm/heap.h"
 #include "vm/memory_region.h"
@@ skipping 2284 matching lines @@
 void Assembler::LeaveFrame() {
   movq(RSP, RBP);
   popq(RBP);
 }
 
 
 void Assembler::ReserveAlignedFrameSpace(intptr_t frame_space) {
   // Reserve space for arguments and align frame before entering
   // the C++ world.
   AddImmediate(RSP, Immediate(-frame_space));
-  if (OS::ActivationFrameAlignment() > 0) {
+  if (OS::ActivationFrameAlignment() > 1) {
     andq(RSP, Immediate(~(OS::ActivationFrameAlignment() - 1)));
   }
 }
 
 
 // TODO(srdjan): Add XMM registers once they are used by the compiler.
 // Based on http://x86-64.org/documentation/abi.pdf Fig. 3.4
 static const intptr_t kNumberOfVolatileCpuRegisters = 9;
 static const Register volatile_cpu_registers[kNumberOfVolatileCpuRegisters] = {
     RAX, RCX, RDX, RSI, RDI, R8, R9, R10, R11
@@ skipping 328 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