Fix build warning after llvm rebranch: Alignment::operator MaybeAlign()

Author: atrick

lib/IRGen/IRGen.h

@@ -263,6 +263,8 @@ class Alignment {
 
   explicit operator bool() const { return Value != 0; }
 
+  explicit operator llvm::MaybeAlign() const { return llvm::MaybeAlign(Value); }
+
   friend bool operator< (Alignment L, Alignment R){ return L.Value <  R.Value; }
   friend bool operator<=(Alignment L, Alignment R){ return L.Value <= R.Value; }
   friend bool operator> (Alignment L, Alignment R){ return L.Value >  R.Value; }

lib/IRGen/TypeLayout.cpp

@@ -1270,8 +1270,8 @@ static void emitMemCpy(IRGenFunction &IGF, Address dest, Address src,
   auto byteDestAddr = Builder.CreateBitOrPointerCast(dest.getAddress(), IGM.Int8PtrTy);
   auto byteSrcAddr =
       Builder.CreateBitOrPointerCast(src.getAddress(), IGM.Int8PtrTy);
-  Builder.CreateMemCpy(byteDestAddr, dest.getAlignment().getValue(),
-                       byteSrcAddr, src.getAlignment().getValue(), size);
+  Builder.CreateMemCpy(byteDestAddr, llvm::MaybeAlign(dest.getAlignment()),
+                       byteSrcAddr, llvm::MaybeAlign(src.getAlignment()), size);
 }
 
 llvm::BasicBlock *