Reuse data fragments while lowering

include/llvm/MC/MCAsmLayout.h

 //===- MCAsmLayout.h - Assembly Layout Object -------------------*- C++ -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_MC_MCASMLAYOUT_H
@@ skipping 41 matching lines @@
   MCAsmLayout(MCAssembler &_Assembler);
 
   /// Get the assembler object this is a layout for.
   MCAssembler &getAssembler() const { return Assembler; }
 
   /// \brief Update the layout because a fragment has been resized. The
   /// fragments size should have already been updated, the \arg SlideAmount is
   /// the delta from the old size.
   void UpdateForSlide(MCFragment *F, int SlideAmount);
 
-  /// \brief Update the layout because a fragment has been replaced.
-  void FragmentReplaced(MCFragment *Src, MCFragment *Dst);
+  /// \brief Update the layout, replacing Src with Dst. The contents
+  /// of Src and Dst are not modified, and must be copied by the caller.
+  /// Src will be removed from the layout, but not deleted.
+  void ReplaceFragment(MCFragment *Src, MCFragment *Dst);
+
+  /// \brief Update the layout to coalesce Src into Dst. The contents
+  /// of Src and Dst are not modified, and must be coalesced by the caller.
+  /// Src will be removed from the layout, but not deleted.
+  void CoalesceFragments(MCFragment *Src, MCFragment *Dst);
 
   /// \brief Perform a full layout.
   void LayoutFile();
 
   /// \brief Perform layout for a single fragment, assuming that the previous
   /// fragment has already been layed out correctly, and the parent section has
   /// been initialized.
   void LayoutFragment(MCFragment *Fragment);
 
   /// \brief Performs initial layout for a single section, assuming that the
@@ skipping 52 matching lines @@
   /// \brief Get the address of the given symbol, as computed in the current
   /// layout.
   uint64_t getSymbolAddress(const MCSymbolData *SD) const;
 
   /// @}
 };
 
 } // end namespace llvm
 
 #endif