Clean up emitInst() in the integrated ARM assembler.

src/IceAssemblerARM32.h

 //===- subzero/src/IceAssemblerARM32.h - Assembler for ARM32 ----*- C++ -*-===//
 //
 // 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.
 //
 // Modified by the Subzero authors.
 //
 //===----------------------------------------------------------------------===//
 //
@@ skipping 437 matching lines @@
     DA_W = (0 | 0 | 1) << 21, // decrement after with writeback to base
     IA_W = (0 | 4 | 1) << 21, // increment after with writeback to base
     DB_W = (8 | 0 | 1) << 21, // decrement before with writeback to base
     IB_W = (8 | 4 | 1) << 21  // increment before with writeback to base
   };
 
   Label *getOrCreateLabel(SizeT Number, LabelVector &Labels);
 
   void bindCfgNodeLabel(const CfgNode *Node) override;
 
-  void emitInst(IValueT Value) { Buffer.emit<IValueT>(Value); }
+  void emitInst(IValueT Value) {
+    AssemblerBuffer::EnsureCapacity ensured(&Buffer);

[Jim Stichnoth, 2016/01/25 16:57:14]

John has a coding style I like where these RAII placeholder variables are named
"_".  I.e.:

  AssemblerBuffer::EnsureCapacity _(&Buffer);

[Karl, 2016/01/25 17:14:07]

I really don't like this style! However, if we are using it, so will I.

+    Buffer.emit<IValueT>(Value);
+  }
 
   // List of possible checks to apply when calling emitType01() (below).
   enum EmitChecks { NoChecks, RdIsPcAndSetFlags };
 
   // Pattern cccctttoooosnnnnddddiiiiiiiiiiii where cccc=Cond, ttt=InstType,
   // s=SetFlags, oooo=Opcode, nnnn=Rn, dddd=Rd, iiiiiiiiiiii=imm12 (See ARM
   // section A5.2.3).
   void emitType01(CondARM32::Cond Cond, IValueT InstType, IValueT Opcode,
                   bool SetFlags, IValueT Rn, IValueT Rd, IValueT imm12,
                   EmitChecks RuleChecks, const char *InstName);
@@ skipping 109 matching lines @@
 
   // Emit VFP instruction with 3 S registers.
   void emitVFPsss(CondARM32::Cond Cond, IValueT Opcode, IValueT Sd, IValueT Sn,
                   IValueT Sm);
 };
 
 } // end of namespace ARM32
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICEASSEMBLERARM32_H