noinline in where clauses again

[Simon Peyton-Jones]

Duncan,

I implemented this a couple of weeks ago but forgot to push it.  Now INLINE pragmas survive across interface files.  I hope it's useful.

Simon

| -----Original Message-----
| From: glasgow-haskell-users-bounces at haskell.org [mailto:glasgow-haskell-users-bounces at haskell.org] On
| Behalf Of Duncan Coutts
| Sent: 14 March 2007 11:59
| To: glasgow-haskell-users at haskell.org
| Subject: noinline in where clauses again
|
| I winged before about NOINLINE pragma on things defined locally in a
| where clause not doing what I expected:
|
| http://www.mail-archive.com/glasgow-haskell-users@haskell.org/msg10338.html
|
| Turns out that one was fixed in ghc HEAD.
|
| I've got another similar one which is not working as I expect in 6.6 or
| in head from 1st March.
|
| This example is from an experimental re-implementation of the Put monad
| in Data.Binary:
|
| write :: Int -> (Ptr Word8 -> IO ()) -> Put ()
| write !n body = Put $ \c buf@(Buffer fp o u l) ->
|   if n <= l
|     then write' c fp o u l
|     else write' (flushOld c n fp o u) (newBuffer c n) 0 0 0
|
|   where {-# NOINLINE write' #-}
|         write' c !fp !o !u !l =
|           -- warning: this is a tad hardcore
|           B.inlinePerformIO
|             (withForeignPtr fp
|               (\p -> body $! (p `plusPtr` (o+u))))
|           `seq` c () (Buffer fp o (u+n) (l-n))
| {-# INLINE [1] write #-}
|
| Then we use it with things like
|
| word8 :: Word8 -> Put ()
| word8 !w = write 1 (pokeWord8 w)
|
| pokeWord8 :: Word8 -> Ptr Word8 -> IO ()
| pokeWord8 w p = poke p w
|
| Then there's a rule so that things like:
|
| foo :: Word8 -> Put ()
| foo !n = do
|   word8 n
|   word8 (n+1)
|   word8 (n+17)
|
| get turned into a single call to write.
|
| Anyway, the point is that when we look at the stg/core we see that in
| write above, the write' has been inlined at the two call sites where as
| I want both branches of the if test to make calls to write'.
|
| The code is here:
| http://haskell.org/~duncan/binary/PutMonad.hs
| http://haskell.org/~duncan/binary/PutTest.hs
|
| the stg from ghc-6.6 is:
| http://haskell.org/~duncan/binary/PutTest.stg
|
| with ghc head from 1st March the result is different but still inlines
| write' in both branches.
|
| Duncan
|
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