Cherry-pick r234714: [MC] Write padding into fragments when -mc-relax-all flag is used

include/llvm/MC/MCAssembler.h

Index: include/llvm/MC/MCAssembler.h
diff --git a/include/llvm/MC/MCAssembler.h b/include/llvm/MC/MCAssembler.h
index 681a317287992794c2f9bb10ec3cab197e32311c..10efc09ed1424de649385563425d98bfedb4753a 100644
--- a/include/llvm/MC/MCAssembler.h
+++ b/include/llvm/MC/MCAssembler.h
@@ -1243,11 +1243,23 @@ public:
       FileNames.push_back(FileName);
   }
 
+  /// \brief Write the necessary bundle padding to the given object writer.
+  /// Expects a fragment \p F containing instructions and its size \p FSize.
+  void writeFragmentPadding(const MCFragment &F, uint64_t FSize,
+                            MCObjectWriter *OW) const;
+
   /// @}
 
   void dump();
 };
 
+/// \brief Compute the amount of padding required before the fragment \p F to
+/// obey bundling restrictions, where \p FOffset is the fragment's offset in
+/// its section and \p FSize is the fragment's size.
+uint64_t computeBundlePadding(const MCAssembler &Assembler,
+                              const MCFragment *F,
+                              uint64_t FOffset, uint64_t FSize);
+
 } // end namespace llvm
 
 #endif