Handle ARM "ret void" and function alignment with proper padding.

src/assembler.h

 //===- subzero/src/assembler.h - Integrated assembler -----------*- C++ -*-===//
 // 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.
 //
 // Modified by the Subzero authors.
 //
 //===----------------------------------------------------------------------===//
 //
 //                        The Subzero Code Generator
@@ skipping 164 matching lines @@
   template <typename T> T *Allocate() { return Allocator.Allocate<T>(); }
 
   // Align the tail end of the function to the required target alignment.
   virtual void alignFunction() = 0;
 
   // Add nop padding of a particular width to the current bundle.
   virtual void padWithNop(intptr_t Padding) = 0;
 
   virtual SizeT getBundleAlignLog2Bytes() const = 0;
 
+  virtual const char *getNonExecPadDirective() const = 0;
   virtual llvm::ArrayRef<uint8_t> getNonExecBundlePadding() const = 0;
 
   // Mark the current text location as the start of a CFG node
   // (represented by NodeNumber).
   virtual void BindCfgNodeLabel(SizeT NodeNumber) = 0;
 
   virtual bool fixupIsPCRel(FixupKind Kind) const = 0;
 
   // Return a view of all the bytes of code for the current function.
   llvm::StringRef getBufferView() const;
@@ skipping 28 matching lines @@
   // relocation fixups are fully committed (Preliminary=false).
   bool Preliminary;
 
 protected:
   AssemblerBuffer buffer_;
 };
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ASSEMBLER_H_