Add some Haddocks to SMRep

1 files changed, 13 insertions, 2 deletions

diff --git a/compiler/cmm/SMRep.lhs b/compiler/cmm/SMRep.lhs
index 9fab530b7f..0713620c5a 100644
--- a/compiler/cmm/SMRep.lhs
+++ b/compiler/cmm/SMRep.lhs
@@ -71,19 +71,30 @@ import Data.Bits
 %************************************************************************
 
 \begin{code}
-type WordOff = Int -- Word offset, or word count
-type ByteOff = Int -- Byte offset, or byte count
+-- | Word offset, or word count
+type WordOff = Int
 
+-- | Byte offset, or byte count
+type ByteOff = Int
+
+-- | Round up the given byte count to the next byte count that's a
+-- multiple of the machine's word size.
 roundUpToWords :: DynFlags -> ByteOff -> ByteOff
 roundUpToWords dflags n =
   (n + (wORD_SIZE dflags - 1)) .&. (complement (wORD_SIZE dflags - 1))
 
+-- | Convert the given number of words to a number of bytes.
+--
+-- This function morally has type @WordOff -> ByteOff@, but uses @Num
+-- a@ to allow for overloading.
 wordsToBytes :: Num a => DynFlags -> a -> a
 wordsToBytes dflags n = fromIntegral (wORD_SIZE dflags) * n
 {-# SPECIALIZE wordsToBytes :: DynFlags -> Int -> Int #-}
 {-# SPECIALIZE wordsToBytes :: DynFlags -> Word -> Word #-}
 {-# SPECIALIZE wordsToBytes :: DynFlags -> Integer -> Integer #-}
 
+-- | First round the given byte count up to a multiple of the
+-- machine's word size and then convert the result to words.
 bytesToWordsRoundUp :: DynFlags -> ByteOff -> WordOff
 bytesToWordsRoundUp dflags n = (n + word_size - 1) `quot` word_size
  where word_size = wORD_SIZE dflags