[Git][ghc/ghc][wip/keepAlive-the-return-of-the-primop] 16 commits: GHC.Utils.Binary: Eliminate allocating withForeignPtr uses

Ben Gamari gitlab at gitlab.haskell.org
Fri Dec 4 03:20:00 UTC 2020



Ben Gamari pushed to branch wip/keepAlive-the-return-of-the-primop at Glasgow Haskell Compiler / GHC


Commits:
d935c519 by Ben Gamari at 2020-12-03T17:18:24-05:00
GHC.Utils.Binary: Eliminate allocating withForeignPtr uses

- - - - -
a34cf3d0 by Ben Gamari at 2020-12-03T17:18:24-05:00
base: Eliminate allocating withForeignPtrs from GHC.Event.Array

- - - - -
9787420a by Ben Gamari at 2020-12-03T17:18:24-05:00
base: Use unsafeWithForeignPtr in GHC.IO.Buffer

- - - - -
397776c9 by Ben Gamari at 2020-12-03T17:18:24-05:00
base: Use unsafeWithForeignPtr in GHC.Event.IntTable

- - - - -
ade9666d by Ben Gamari at 2020-12-03T17:18:24-05:00
Bump bytestring submodule

Teach it to use unsafeWithForeignPtr where appropriate.

- - - - -
8b249760 by Ben Gamari at 2020-12-03T17:18:24-05:00
Sized

- - - - -
10217769 by Ben Gamari at 2020-12-03T17:18:24-05:00
StringBuffer: Use unsafeWithForeignPtr

- - - - -
0bd3eb8d by Ben Gamari at 2020-12-03T17:26:14-05:00
genprimopcode: Add a second levity-polymorphic tyvar

This will be needed shortly.

- - - - -
934d56fc by GHC GitLab CI at 2020-12-03T17:26:14-05:00
Introduce keepAlive primop

- - - - -
da7af3b3 by Ben Gamari at 2020-12-03T17:26:14-05:00
base: Use keepAlive# in withForeignPtr

- - - - -
b0b95338 by Ben Gamari at 2020-12-03T17:26:14-05:00
Implement withByteArrayContents in terms of keepAlive#

- - - - -
44b0f9b3 by Ben Gamari at 2020-12-03T17:26:14-05:00
base: Implement GHC.ForeignPtr.Ops in terms of keepAlive#

- - - - -
df0a7551 by Ben Gamari at 2020-12-03T17:26:14-05:00
base: Use keepAlive# in Foreign.Marshal.Alloc

- - - - -
cccd9dbe by Ben Gamari at 2020-12-03T17:26:14-05:00
ghc-compact: Use keepAlive# in GHC.Compact.Serialized

- - - - -
806283f2 by Ben Gamari at 2020-12-03T17:26:14-05:00
iFix it

- - - - -
8ae19c3a by Ben Gamari at 2020-12-03T17:26:14-05:00
testsuite fixes

Metric Increase:
    T10421
    T12227
    T12234
    T12425
    T13035
    T5536

- - - - -


18 changed files:

- compiler/GHC/Builtin/primops.txt.pp
- compiler/GHC/Core/Utils.hs
- compiler/GHC/CoreToStg/Prep.hs
- compiler/GHC/Data/ByteArray.hs
- compiler/GHC/Data/StringBuffer.hs
- compiler/GHC/StgToCmm/Prim.hs
- compiler/GHC/Utils/Binary.hs
- libraries/base/Foreign/Marshal/Alloc.hs
- libraries/base/GHC/Event/Array.hs
- libraries/base/GHC/Event/IntTable.hs
- libraries/base/GHC/ForeignPtr.hs
- libraries/base/GHC/ForeignPtr/Ops.hs
- libraries/base/GHC/IO/Buffer.hs
- libraries/bytestring
- libraries/ghc-compact/GHC/Compact/Serialized.hs
- testsuite/tests/ghci/should_run/T16012.script
- testsuite/tests/ghci/should_run/T16012.stdout
- utils/genprimopcode/Main.hs


Changes:

=====================================
compiler/GHC/Builtin/primops.txt.pp
=====================================
@@ -2983,6 +2983,20 @@ primop NumSparks "numSparks#" GenPrimOp
    has_side_effects = True
    out_of_line = True
 
+
+------------------------------------------------------------------------
+section "Controlling object lifetime"
+        {Ensuring that objects don't die a premature death.}
+------------------------------------------------------------------------
+
+-- See Note [keepAlive# magic] in GHC.CoreToStg.Prep.
+primop KeepAliveOp "keepAlive#" GenPrimOp
+   o -> State# RealWorld -> (State# RealWorld -> p) -> p
+   { TODO. }
+   with
+   strictness = { \ _arity -> mkClosedStrictSig [topDmd, topDmd, strictOnceApply1Dmd] topDiv }
+
+
 ------------------------------------------------------------------------
 section "Tag to enum stuff"
         {Convert back and forth between values of enumerated types


=====================================
compiler/GHC/Core/Utils.hs
=====================================
@@ -1642,6 +1642,8 @@ app_ok primop_ok fun args
         -> False       --     for the special cases for SeqOp and DataToTagOp
         | DataToTagOp <- op
         -> False
+        | KeepAliveOp <- op
+        -> False
 
         | otherwise
         -> primop_ok op  -- Check the primop itself


=====================================
compiler/GHC/CoreToStg/Prep.hs
=====================================
@@ -32,7 +32,10 @@ import GHC.Tc.Utils.Env
 import GHC.Unit
 
 import GHC.Builtin.Names
+import GHC.Builtin.PrimOps
 import GHC.Builtin.Types
+import GHC.Builtin.Types.Prim ( realWorldStatePrimTy )
+import GHC.Types.Id.Make ( realWorldPrimId, mkPrimOpId )
 
 import GHC.Core.Utils
 import GHC.Core.Opt.Arity
@@ -47,6 +50,7 @@ import GHC.Core.TyCon
 import GHC.Core.DataCon
 import GHC.Core.Opt.OccurAnal
 
+
 import GHC.Data.Maybe
 import GHC.Data.OrdList
 import GHC.Data.FastString
@@ -63,7 +67,6 @@ import GHC.Types.Var.Set
 import GHC.Types.Var.Env
 import GHC.Types.Id
 import GHC.Types.Id.Info
-import GHC.Types.Id.Make ( realWorldPrimId )
 import GHC.Types.Basic
 import GHC.Types.Name   ( NamedThing(..), nameSrcSpan, isInternalName )
 import GHC.Types.SrcLoc ( SrcSpan(..), realSrcLocSpan, mkRealSrcLoc )
@@ -784,6 +787,38 @@ cpeApp top_env expr
         -- rather than the far superior "f x y".  Test case is par01.
         = let (terminal, args', depth') = collect_args arg
           in cpe_app env terminal (args' ++ args) (depth + depth' - 1)
+
+    cpe_app env
+            (Var f)
+            args
+            n
+        | Just KeepAliveOp <- isPrimOpId_maybe f
+        , CpeApp (Type arg_rep)
+          : CpeApp (Type arg_ty)
+          : CpeApp (Type _result_rep)
+          : CpeApp (Type result_ty)
+          : CpeApp arg
+          : CpeApp s0
+          : CpeApp k
+          : rest <- pprTrace "cpe_app keepAlive#" (ppr args) args
+        = do { pprTraceM "cpe_app(keepAlive#)" (ppr n)
+             ; y <- newVar result_ty
+             ; s2 <- newVar realWorldStatePrimTy
+             ; -- beta reduce if possible
+             ; (floats, k') <- case k of
+                  Lam s body -> cpe_app (extendCorePrepEnvExpr env s s0) body rest (n-2)
+                  _          -> cpe_app env k (CpeApp s0 : rest) (n-1)
+             ; let touchId = mkPrimOpId TouchOp
+                   expr = Case k' y result_ty [(DEFAULT, [], rhs)]
+                   rhs = let scrut = mkApps (Var touchId) [Type arg_rep, Type arg_ty, arg, Var realWorldPrimId]
+                         in Case scrut s2 result_ty [(DEFAULT, [], Var y)]
+             ; pprTraceM "cpe_app(keepAlive)" (ppr expr)
+             ; (floats', expr') <- cpeBody env expr
+             ; return (floats `appendFloats` floats', expr')
+             }
+        | Just KeepAliveOp <- isPrimOpId_maybe f
+        = panic "invalid keepAlive# application"
+
     cpe_app env (Var f) (CpeApp _runtimeRep at Type{} : CpeApp _type at Type{} : CpeApp arg : rest) n
         | f `hasKey` runRWKey
         -- N.B. While it may appear that n == 1 in the case of runRW#


=====================================
compiler/GHC/Data/ByteArray.hs
=====================================
@@ -77,10 +77,15 @@ unsafeMutableByteArrayContents :: MutableByteArray -> Ptr a
 unsafeMutableByteArrayContents = unsafeByteArrayContents . unsafeCoerce
 
 withByteArrayContents :: ByteArray -> (Ptr a -> IO b) -> IO b
+#if MIN_VERSION_base(4,15,0)
+withByteArrayContents (ByteArray ba) f =
+  IO $ \s -> keepAlive# ba s (unIO (f (Ptr (byteArrayContents# ba))))
+#else
 withByteArrayContents (ByteArray ba) f = do
   r <- f $ Ptr (byteArrayContents# ba)
   IO $ \s -> case touch# ba s of s' -> (# s', () #)
   return r
+#endif
 
 newMutableByteArray :: Int -> IO MutableByteArray
 newMutableByteArray (I# size) = IO $ \s ->


=====================================
compiler/GHC/Data/StringBuffer.hs
=====================================
@@ -68,6 +68,12 @@ import GHC.IO.Encoding.Failure  ( CodingFailureMode(IgnoreCodingFailure) )
 import GHC.Exts
 
 import Foreign
+#if MIN_VERSION_base(4,15,0)
+import GHC.ForeignPtr (unsafeWithForeignPtr)
+#else
+unsafeWithForeignPtr :: ForeignPtr a -> (Ptr a -> IO b) -> IO b
+unsafeWithForeignPtr = withForeignPtr
+#endif
 
 -- -----------------------------------------------------------------------------
 -- The StringBuffer type
@@ -107,7 +113,7 @@ hGetStringBuffer fname = do
    offset_i <- skipBOM h size_i 0  -- offset is 0 initially
    let size = fromIntegral $ size_i - offset_i
    buf <- mallocForeignPtrArray (size+3)
-   withForeignPtr buf $ \ptr -> do
+   unsafeWithForeignPtr buf $ \ptr -> do
      r <- if size == 0 then return 0 else hGetBuf h ptr size
      hClose h
      if (r /= size)
@@ -120,7 +126,7 @@ hGetStringBufferBlock handle wanted
          offset_i <- hTell handle >>= skipBOM handle size_i
          let size = min wanted (fromIntegral $ size_i-offset_i)
          buf <- mallocForeignPtrArray (size+3)
-         withForeignPtr buf $ \ptr ->
+         unsafeWithForeignPtr buf $ \ptr ->
              do r <- if size == 0 then return 0 else hGetBuf handle ptr size
                 if r /= size
                    then ioError (userError $ "short read of file: "++show(r,size,size_i,handle))
@@ -128,7 +134,7 @@ hGetStringBufferBlock handle wanted
 
 hPutStringBuffer :: Handle -> StringBuffer -> IO ()
 hPutStringBuffer hdl (StringBuffer buf len cur)
-    = withForeignPtr (plusForeignPtr buf cur) $ \ptr ->
+    = unsafeWithForeignPtr (plusForeignPtr buf cur) $ \ptr ->
           hPutBuf hdl ptr len
 
 -- | Skip the byte-order mark if there is one (see #1744 and #6016),
@@ -165,9 +171,9 @@ newUTF8StringBuffer buf ptr size = do
 appendStringBuffers :: StringBuffer -> StringBuffer -> IO StringBuffer
 appendStringBuffers sb1 sb2
     = do newBuf <- mallocForeignPtrArray (size+3)
-         withForeignPtr newBuf $ \ptr ->
-          withForeignPtr (buf sb1) $ \sb1Ptr ->
-           withForeignPtr (buf sb2) $ \sb2Ptr ->
+         unsafeWithForeignPtr newBuf $ \ptr ->
+          unsafeWithForeignPtr (buf sb1) $ \sb1Ptr ->
+           unsafeWithForeignPtr (buf sb2) $ \sb2Ptr ->
              do copyArray ptr (sb1Ptr `advancePtr` cur sb1) sb1_len
                 copyArray (ptr `advancePtr` sb1_len) (sb2Ptr `advancePtr` cur sb2) sb2_len
                 pokeArray (ptr `advancePtr` size) [0,0,0]
@@ -184,7 +190,7 @@ stringToStringBuffer str =
  unsafePerformIO $ do
   let size = utf8EncodedLength str
   buf <- mallocForeignPtrArray (size+3)
-  withForeignPtr buf $ \ptr -> do
+  unsafeWithForeignPtr buf $ \ptr -> do
     utf8EncodeString ptr str
     pokeArray (ptr `plusPtr` size :: Ptr Word8) [0,0,0]
     -- sentinels for UTF-8 decoding
@@ -203,7 +209,7 @@ nextChar :: StringBuffer -> (Char,StringBuffer)
 nextChar (StringBuffer buf len (I# cur#)) =
   -- Getting our fingers dirty a little here, but this is performance-critical
   inlinePerformIO $
-    withForeignPtr buf $ \(Ptr a#) ->
+    unsafeWithForeignPtr buf $ \(Ptr a#) ->
         case utf8DecodeCharAddr# (a# `plusAddr#` cur#) 0# of
           (# c#, nBytes# #) ->
              let cur' = I# (cur# +# nBytes#) in
@@ -220,7 +226,7 @@ prevChar :: StringBuffer -> Char -> Char
 prevChar (StringBuffer _   _   0)   deflt = deflt
 prevChar (StringBuffer buf _   cur) _     =
   inlinePerformIO $
-    withForeignPtr buf $ \p -> do
+    unsafeWithForeignPtr buf $ \p -> do
       p' <- utf8PrevChar (p `plusPtr` cur)
       return (fst (utf8DecodeChar p'))
 
@@ -258,7 +264,7 @@ atEnd (StringBuffer _ l c) = l == c
 atLine :: Int -> StringBuffer -> Maybe StringBuffer
 atLine line sb@(StringBuffer buf len _) =
   inlinePerformIO $
-    withForeignPtr buf $ \p -> do
+    unsafeWithForeignPtr buf $ \p -> do
       p' <- skipToLine line len p
       if p' == nullPtr
         then return Nothing
@@ -309,14 +315,14 @@ lexemeToFastString :: StringBuffer
 lexemeToFastString _ 0 = nilFS
 lexemeToFastString (StringBuffer buf _ cur) len =
    inlinePerformIO $
-     withForeignPtr buf $ \ptr ->
+     unsafeWithForeignPtr buf $ \ptr ->
        return $! mkFastStringBytes (ptr `plusPtr` cur) len
 
 -- | Return the previous @n@ characters (or fewer if we are less than @n@
 -- characters into the buffer.
 decodePrevNChars :: Int -> StringBuffer -> String
 decodePrevNChars n (StringBuffer buf _ cur) =
-    inlinePerformIO $ withForeignPtr buf $ \p0 ->
+    inlinePerformIO $ unsafeWithForeignPtr buf $ \p0 ->
       go p0 n "" (p0 `plusPtr` (cur - 1))
   where
     go :: Ptr Word8 -> Int -> String -> Ptr Word8 -> IO String


=====================================
compiler/GHC/StgToCmm/Prim.hs
=====================================
@@ -1551,6 +1551,8 @@ emitPrimOp dflags primop = case primop of
   TraceMarkerOp -> alwaysExternal
   SetThreadAllocationCounter -> alwaysExternal
 
+  KeepAliveOp -> panic "keepAlive# should have been eliminated in CorePrep"
+
  where
   profile = targetProfile dflags
   platform = profilePlatform profile


=====================================
compiler/GHC/Utils/Binary.hs
=====================================
@@ -6,6 +6,7 @@
 {-# LANGUAGE BangPatterns #-}
 {-# LANGUAGE StandaloneDeriving #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE UnboxedTuples #-}
 
 {-# OPTIONS_GHC -O2 -funbox-strict-fields #-}
 -- We always optimise this, otherwise performance of a non-optimised
@@ -93,10 +94,16 @@ import System.IO as IO
 import System.IO.Unsafe         ( unsafeInterleaveIO )
 import System.IO.Error          ( mkIOError, eofErrorType )
 import GHC.Real                 ( Ratio(..) )
+#if MIN_VERSION_base(4,15,0)
+import GHC.ForeignPtr           ( unsafeWithForeignPtr )
+#endif
 
 type BinArray = ForeignPtr Word8
 
-
+#if !MIN_VERSION_base(4,15,0)
+unsafeWithForeignPtr :: ForeignPtr a -> (Ptr a -> IO b) -> IO b
+unsafeWithForeignPtr = withForeignPtr
+#endif
 
 ---------------------------------------------------------------
 -- BinData
@@ -111,14 +118,14 @@ instance Binary BinData where
   put_ bh (BinData sz dat) = do
     put_ bh sz
     putPrim bh sz $ \dest ->
-      withForeignPtr dat $ \orig ->
+      unsafeWithForeignPtr dat $ \orig ->
         copyBytes dest orig sz
   --
   get bh = do
     sz <- get bh
     dat <- mallocForeignPtrBytes sz
     getPrim bh sz $ \orig ->
-      withForeignPtr dat $ \dest ->
+      unsafeWithForeignPtr dat $ \dest ->
         copyBytes dest orig sz
     return (BinData sz dat)
 
@@ -226,7 +233,7 @@ writeBinMem (BinMem _ ix_r _ arr_r) fn = do
   h <- openBinaryFile fn WriteMode
   arr <- readIORef arr_r
   ix  <- readFastMutInt ix_r
-  withForeignPtr arr $ \p -> hPutBuf h p ix
+  unsafeWithForeignPtr arr $ \p -> hPutBuf h p ix
   hClose h
 
 readBinMem :: FilePath -> IO BinHandle
@@ -236,7 +243,7 @@ readBinMem filename = do
   filesize' <- hFileSize h
   let filesize = fromIntegral filesize'
   arr <- mallocForeignPtrBytes filesize
-  count <- withForeignPtr arr $ \p -> hGetBuf h p filesize
+  count <- unsafeWithForeignPtr arr $ \p -> hGetBuf h p filesize
   when (count /= filesize) $
        error ("Binary.readBinMem: only read " ++ show count ++ " bytes")
   hClose h
@@ -280,7 +287,7 @@ putPrim h@(BinMem _ ix_r sz_r arr_r) size f = do
   when (ix + size > sz) $
     expandBin h (ix + size)
   arr <- readIORef arr_r
-  withForeignPtr arr $ \op -> f (op `plusPtr` ix)
+  unsafeWithForeignPtr arr $ \op -> f (op `plusPtr` ix)
   writeFastMutInt ix_r (ix + size)
 
 -- -- | Similar to putPrim but advances the index by the actual number of
@@ -302,7 +309,9 @@ getPrim (BinMem _ ix_r sz_r arr_r) size f = do
   when (ix + size > sz) $
       ioError (mkIOError eofErrorType "Data.Binary.getPrim" Nothing Nothing)
   arr <- readIORef arr_r
-  w <- withForeignPtr arr $ \op -> f (op `plusPtr` ix)
+  w <- unsafeWithForeignPtr arr $ \p -> f (p `plusPtr` ix)
+    -- This is safe WRT #17760 as we we guarantee that the above line doesn't
+    -- diverge
   writeFastMutInt ix_r (ix + size)
   return w
 


=====================================
libraries/base/Foreign/Marshal/Alloc.hs
=====================================
@@ -116,19 +116,6 @@ alloca :: forall a b . Storable a => (Ptr a -> IO b) -> IO b
 alloca  =
   allocaBytesAligned (sizeOf (undefined :: a)) (alignment (undefined :: a))
 
--- Note [NOINLINE for touch#]
--- ~~~~~~~~~~~~~~~~~~~~~~~~~~
--- Both allocaBytes and allocaBytesAligned use the touch#, which is notoriously
--- fragile in the presence of simplification (see #14346). In particular, the
--- simplifier may drop the continuation containing the touch# if it can prove
--- that the action passed to allocaBytes will not return. The hack introduced to
--- fix this for 8.2.2 is to mark allocaBytes as NOINLINE, ensuring that the
--- simplifier can't see the divergence.
---
--- These can be removed once #14375 is fixed, which suggests that we instead do
--- away with touch# in favor of a primitive that will capture the scoping left
--- implicit in the case of touch#.
-
 -- |@'allocaBytes' n f@ executes the computation @f@, passing as argument
 -- a pointer to a temporarily allocated block of memory of @n@ bytes.
 -- The block of memory is sufficiently aligned for any of the basic
@@ -143,12 +130,8 @@ allocaBytes (I# size) action = IO $ \ s0 ->
      case unsafeFreezeByteArray# mbarr# s1 of { (# s2, barr#  #) ->
      let addr = Ptr (byteArrayContents# barr#) in
      case action addr     of { IO action' ->
-     case action' s2      of { (# s3, r #) ->
-     case touch# barr# s3 of { s4 ->
-     (# s4, r #)
-  }}}}}
--- See Note [NOINLINE for touch#]
-{-# NOINLINE allocaBytes #-}
+     keepAlive# barr# s2 action'
+  }}}
 
 allocaBytesAligned :: Int -> Int -> (Ptr a -> IO b) -> IO b
 allocaBytesAligned (I# size) (I# align) action = IO $ \ s0 ->
@@ -156,12 +139,8 @@ allocaBytesAligned (I# size) (I# align) action = IO $ \ s0 ->
      case unsafeFreezeByteArray# mbarr# s1 of { (# s2, barr#  #) ->
      let addr = Ptr (byteArrayContents# barr#) in
      case action addr     of { IO action' ->
-     case action' s2      of { (# s3, r #) ->
-     case touch# barr# s3 of { s4 ->
-     (# s4, r #)
-  }}}}}
--- See Note [NOINLINE for touch#]
-{-# NOINLINE allocaBytesAligned #-}
+     keepAlive# barr# s2 action'
+  }}}
 
 -- |Resize a memory area that was allocated with 'malloc' or 'mallocBytes'
 -- to the size needed to store values of type @b at .  The returned pointer


=====================================
libraries/base/GHC/Event/Array.hs
=====================================
@@ -33,7 +33,7 @@ import Foreign.ForeignPtr (ForeignPtr, withForeignPtr)
 import Foreign.Ptr (Ptr, nullPtr, plusPtr)
 import Foreign.Storable (Storable(..))
 import GHC.Base hiding (empty)
-import GHC.ForeignPtr (mallocPlainForeignPtrBytes, newForeignPtr_)
+import GHC.ForeignPtr (mallocPlainForeignPtrBytes, newForeignPtr_, unsafeWithForeignPtr)
 import GHC.Num (Num(..))
 import GHC.Real (fromIntegral)
 import GHC.Show (show)
@@ -78,9 +78,9 @@ reallocArray p newSize oldSize = reallocHack undefined p
   reallocHack dummy src = do
       let size = sizeOf dummy
       dst <- mallocPlainForeignPtrBytes (newSize * size)
-      withForeignPtr src $ \s ->
+      unsafeWithForeignPtr src $ \s ->
         when (s /= nullPtr && oldSize > 0) .
-          withForeignPtr dst $ \d -> do
+          unsafeWithForeignPtr dst $ \d -> do
             _ <- memcpy d s (fromIntegral (oldSize * size))
             return ()
       return dst
@@ -99,8 +99,8 @@ duplicate a = dupHack undefined a
   dupHack dummy (Array ref) = do
     AC es len cap <- readIORef ref
     ary <- allocArray cap
-    withForeignPtr ary $ \dest ->
-      withForeignPtr es $ \src -> do
+    unsafeWithForeignPtr ary $ \dest ->
+      unsafeWithForeignPtr es $ \src -> do
         _ <- memcpy dest src (fromIntegral (len * sizeOf dummy))
         return ()
     Array `fmap` newIORef (AC ary len cap)
@@ -119,8 +119,8 @@ unsafeRead :: Storable a => Array a -> Int -> IO a
 unsafeRead (Array ref) ix = do
     AC es _ cap <- readIORef ref
     CHECK_BOUNDS("unsafeRead",cap,ix)
-      withForeignPtr es $ \p ->
-        peekElemOff p ix
+      unsafeWithForeignPtr es $ \ptr -> peekElemOff ptr ix
+        -- this is safe WRT #17760 as we assume that peekElemOff doesn't diverge
 
 unsafeWrite :: Storable a => Array a -> Int -> a -> IO ()
 unsafeWrite (Array ref) ix a = do
@@ -130,13 +130,15 @@ unsafeWrite (Array ref) ix a = do
 unsafeWrite' :: Storable a => AC a -> Int -> a -> IO ()
 unsafeWrite' (AC es _ cap) ix a =
     CHECK_BOUNDS("unsafeWrite'",cap,ix)
-      withForeignPtr es $ \p ->
-        pokeElemOff p ix a
+      unsafeWithForeignPtr es $ \ptr -> pokeElemOff ptr ix a
+        -- this is safe WRT #17760 as we assume that peekElemOff doesn't diverge
 
+-- | Precondition: continuation must not diverge due to use of
+-- 'unsafeWithForeignPtr'.
 unsafeLoad :: Array a -> (Ptr a -> Int -> IO Int) -> IO Int
 unsafeLoad (Array ref) load = do
     AC es _ cap <- readIORef ref
-    len' <- withForeignPtr es $ \p -> load p cap
+    len' <- unsafeWithForeignPtr es $ \p -> load p cap
     writeIORef ref (AC es len' cap)
     return len'
 
@@ -146,7 +148,7 @@ unsafeCopyFromBuffer :: Storable a => Array a -> Ptr a -> Int -> IO ()
 unsafeCopyFromBuffer (Array ref) sptr n =
     readIORef ref >>= \(AC es _ cap) ->
     CHECK_BOUNDS("unsafeCopyFromBuffer", cap, n)
-    withForeignPtr es $ \pdest -> do
+    unsafeWithForeignPtr es $ \pdest -> do
       let size = sizeOfPtr sptr undefined
       _ <- memcpy pdest sptr (fromIntegral $ n * size)
       writeIORef ref (AC es n cap)
@@ -198,7 +200,7 @@ forM_ ary g = forHack ary g undefined
       AC es len _ <- readIORef ref
       let size = sizeOf dummy
           offset = len * size
-      withForeignPtr es $ \p -> do
+      unsafeWithForeignPtr es $ \p -> do
         let go n | n >= offset = return ()
                  | otherwise = do
               f =<< peek (p `plusPtr` n)
@@ -269,8 +271,8 @@ copy' d dstart s sstart maxCount = copyHack d s undefined
       then return dac
       else do
         AC dst dlen dcap <- ensureCapacity' dac (dstart + count)
-        withForeignPtr dst $ \dptr ->
-          withForeignPtr src $ \sptr -> do
+        unsafeWithForeignPtr dst $ \dptr ->
+          unsafeWithForeignPtr src $ \sptr -> do
             _ <- memcpy (dptr `plusPtr` (dstart * size))
                         (sptr `plusPtr` (sstart * size))
                         (fromIntegral (count * size))
@@ -286,7 +288,7 @@ removeAt a i = removeHack a undefined
     let size   = sizeOf dummy
         newLen = oldLen - 1
     when (newLen > 0 && i < newLen) .
-      withForeignPtr fp $ \ptr -> do
+      unsafeWithForeignPtr fp $ \ptr -> do
         _ <- memmove (ptr `plusPtr` (size * i))
                      (ptr `plusPtr` (size * (i+1)))
                      (fromIntegral (size * (newLen-i)))


=====================================
libraries/base/GHC/Event/IntTable.hs
=====================================
@@ -17,7 +17,8 @@ module GHC.Event.IntTable
 import Data.Bits ((.&.), shiftL, shiftR)
 import Data.IORef (IORef, newIORef, readIORef, writeIORef)
 import Data.Maybe (Maybe(..), isJust)
-import Foreign.ForeignPtr (ForeignPtr, mallocForeignPtr, withForeignPtr)
+import Foreign.ForeignPtr (ForeignPtr, mallocForeignPtr)
+import GHC.ForeignPtr (unsafeWithForeignPtr)
 import Foreign.Storable (peek, poke)
 import GHC.Base (Monad(..), (=<<), ($), ($!), const, liftM, otherwise, when)
 import GHC.Classes (Eq(..), Ord(..))
@@ -62,7 +63,7 @@ new_ :: Int -> IO (IT a)
 new_ capacity = do
   arr <- Arr.new Empty capacity
   size <- mallocForeignPtr
-  withForeignPtr size $ \ptr -> poke ptr 0
+  unsafeWithForeignPtr size $ \ptr -> poke ptr 0
   return IT { tabArr = arr
             , tabSize = size
             }
@@ -81,7 +82,7 @@ grow oldit ref size = do
                 copyBucket (m+1) bucketNext
           copyBucket n =<< Arr.read (tabArr oldit) i
   copySlot 0 0
-  withForeignPtr (tabSize newit) $ \ptr -> poke ptr size
+  unsafeWithForeignPtr (tabSize newit) $ \ptr -> poke ptr size
   writeIORef ref newit
 
 -- | @insertWith f k v table@ inserts @k@ into @table@ with value @v at .
@@ -100,7 +101,7 @@ insertWith f k v inttable@(IntTable ref) = do
           Arr.write tabArr idx (Bucket k v' next)
           return (Just bucketValue)
         | otherwise = go bkt { bucketNext = seen } bucketNext
-      go seen _ = withForeignPtr tabSize $ \ptr -> do
+      go seen _ = unsafeWithForeignPtr tabSize $ \ptr -> do
         size <- peek ptr
         if size + 1 >= Arr.size tabArr - (Arr.size tabArr `shiftR` 2)
           then grow it ref size >> insertWith f k v inttable
@@ -139,7 +140,7 @@ updateWith f k (IntTable ref) = do
   when (isJust oldVal) $ do
     Arr.write tabArr idx newBucket
     when del $
-      withForeignPtr tabSize $ \ptr -> do
+      unsafeWithForeignPtr tabSize $ \ptr -> do
         size <- peek ptr
         poke ptr (size - 1)
   return oldVal


=====================================
libraries/base/GHC/ForeignPtr.hs
=====================================
@@ -526,7 +526,9 @@ withForeignPtr :: ForeignPtr a -> (Ptr a -> IO b) -> IO b
 -- or from the object pointed to by the
 -- 'ForeignPtr', using the operations from the
 -- 'Storable' class.
-withForeignPtr = unsafeWithForeignPtr
+withForeignPtr fo@(ForeignPtr _ r) f = IO $ \s ->
+  case f (unsafeForeignPtrToPtr fo) of
+    IO action# -> keepAlive# r s action#
 
 -- | This is similar to 'withForeignPtr' but comes with an important caveat:
 -- the user must guarantee that the continuation does not diverge (e.g. loop or


=====================================
libraries/base/GHC/ForeignPtr/Ops.hs
=====================================
@@ -51,121 +51,114 @@ import GHC.Word
 import GHC.Int
 import GHC.Base
 import GHC.ForeignPtr
-import GHC.Ptr
-
-withFP :: ForeignPtr a
-       -> (Addr# -> State# RealWorld -> (# State# RealWorld, b #))
-       -> IO b
-withFP fp f =
-  withForeignPtr fp (\(Ptr addr) -> IO (f addr))
 
 peekWord8ForeignPtr :: ForeignPtr ty -> Int -> IO Word8
-peekWord8ForeignPtr fp (I# d) = withFP fp $ \addr s0 ->
-    case readWord8OffAddr# addr d s0 of
-      (# s1, r #) -> (# s1, W8# r #)
+peekWord8ForeignPtr (ForeignPtr addr c) (I# d) = IO $ \s0 ->
+    case keepAlive# c s0 (readWord8OffAddr# addr d) of
+      (# s1, r #) -> (# s1, W8# (narrowWord8# r) #)
 
 peekWord16ForeignPtr :: ForeignPtr ty -> Int -> IO Word16
-peekWord16ForeignPtr fp (I# d) = withFP fp $ \addr s0 ->
-    case readWord16OffAddr# addr d s0 of
-      (# s1, r #) -> (# s1, W16# r #)
+peekWord16ForeignPtr (ForeignPtr addr c) (I# d) = IO $ \s0 ->
+    case keepAlive# c s0 (readWord16OffAddr# addr d) of
+      (# s1, r #) -> (# s1, W16# (narrowWord16# r) #)
 
 peekWord32ForeignPtr :: ForeignPtr ty -> Int -> IO Word32
-peekWord32ForeignPtr fp (I# d) = withFP fp $ \addr s0 ->
-    case readWord32OffAddr# addr d s0 of
-      (# s1, r #) -> (# s1, W32# r #)
+peekWord32ForeignPtr (ForeignPtr addr c) (I# d) = IO $ \s0 ->
+    case keepAlive# c s0 (readWord32OffAddr# addr d) of
+      (# s1, r #) -> (# s1, W32# (narrowWord32# r) #)
 
 peekWord64ForeignPtr :: ForeignPtr ty -> Int -> IO Word64
-peekWord64ForeignPtr fp (I# d) = withFP fp $ \addr s0 ->
-    case readWord64OffAddr# addr d s0 of
+peekWord64ForeignPtr (ForeignPtr addr c) (I# d) = IO $ \s0 ->
+    case keepAlive# c s0 (readWord64OffAddr# addr d) of
       (# s1, r #) -> (# s1, W64# r #)
 
 peekWordForeignPtr :: ForeignPtr ty -> Int -> IO Word
-peekWordForeignPtr fp (I# d) = withFP fp $ \addr s0 ->
-    case readWordOffAddr# addr d s0 of
+peekWordForeignPtr (ForeignPtr addr c) (I# d) = IO $ \s0 ->
+    case keepAlive# c s0 (readWordOffAddr# addr d) of
       (# s1, r #) -> (# s1, W# r #)
 
 peekInt8ForeignPtr :: ForeignPtr ty -> Int -> IO Int8
-peekInt8ForeignPtr fp (I# d) = withFP fp $ \addr s0 ->
-    case readInt8OffAddr# addr d s0 of
-      (# s1, r #) -> (# s1, I8# r #)
+peekInt8ForeignPtr (ForeignPtr addr c) (I# d) = IO $ \s0 ->
+    case keepAlive# c s0 (readInt8OffAddr# addr d) of
+      (# s1, r #) -> (# s1, I8# (narrowInt8# r) #)
 
 peekInt16ForeignPtr :: ForeignPtr ty -> Int -> IO Int16
-peekInt16ForeignPtr fp (I# d) = withFP fp $ \addr s0 ->
-    case readInt16OffAddr# addr d s0 of
-      (# s1, r #) -> (# s1, I16# r #)
+peekInt16ForeignPtr (ForeignPtr addr c) (I# d) = IO $ \s0 ->
+    case keepAlive# c s0 (readInt16OffAddr# addr d) of
+      (# s1, r #) -> (# s1, I16# (narrowInt16# r) #)
 
 peekInt32ForeignPtr :: ForeignPtr ty -> Int -> IO Int32
-peekInt32ForeignPtr fp (I# d) = withFP fp $ \addr s0 ->
-    case readInt32OffAddr# addr d s0 of
-      (# s1, r #) -> (# s1, I32# r #)
+peekInt32ForeignPtr (ForeignPtr addr c) (I# d) = IO $ \s0 ->
+    case keepAlive# c s0 (readInt32OffAddr# addr d) of
+      (# s1, r #) -> (# s1, I32# (narrowInt32# r) #)
 
 peekInt64ForeignPtr :: ForeignPtr ty -> Int -> IO Int64
-peekInt64ForeignPtr fp (I# d) = withFP fp $ \addr s0 ->
-    case readInt64OffAddr# addr d s0 of
+peekInt64ForeignPtr (ForeignPtr addr c) (I# d) = IO $ \s0 ->
+    case keepAlive# c s0 (readInt64OffAddr# addr d) of
       (# s1, r #) -> (# s1, I64# r #)
 
 peekIntForeignPtr :: ForeignPtr ty -> Int -> IO Int
-peekIntForeignPtr fp (I# d) = withFP fp $ \addr s0 ->
-    case readIntOffAddr# addr d s0 of
+peekIntForeignPtr (ForeignPtr addr c) (I# d) = IO $ \s0 ->
+    case keepAlive# c s0 (readIntOffAddr# addr d) of
       (# s1, r #) -> (# s1, I# r #)
 
 peekCharForeignPtr :: ForeignPtr ty -> Int -> IO Char
-peekCharForeignPtr fp (I# d) = withFP fp $ \addr s0 ->
-    case readCharOffAddr# addr d s0 of
+peekCharForeignPtr (ForeignPtr addr c) (I# d) = IO $ \s0 ->
+    case keepAlive# c s0 (readCharOffAddr# addr d) of
       (# s1, r #) -> (# s1, C# r #)
 
 pokeWord8ForeignPtr :: ForeignPtr ty -> Int -> Word8 -> IO ()
-pokeWord8ForeignPtr fp (I# d) (W8# n) = withFP fp $ \addr s0 ->
-    case writeWord8OffAddr# addr d n s0 of
+pokeWord8ForeignPtr (ForeignPtr addr c) (I# d) (W8# n) = IO $ \s0 ->
+    case keepAlive# c s0 (writeWord8OffAddr# addr d (extendWord8# n)) of
       s1 -> (# s1, () #)
 
 pokeWord16ForeignPtr :: ForeignPtr ty -> Int -> Word16 -> IO ()
-pokeWord16ForeignPtr fp (I# d) (W16# n) = withFP fp $ \addr s0 ->
-    case writeWord16OffAddr# addr d n s0 of
+pokeWord16ForeignPtr (ForeignPtr addr c) (I# d) (W16# n) = IO $ \s0 ->
+    case keepAlive# c s0 (writeWord16OffAddr# addr d (extendWord16# n)) of
       s1 -> (# s1, () #)
 
 pokeWord32ForeignPtr :: ForeignPtr ty -> Int -> Word32 -> IO ()
-pokeWord32ForeignPtr fp (I# d) (W32# n) = withFP fp $ \addr s0 ->
-    case writeWord32OffAddr# addr d n s0 of
+pokeWord32ForeignPtr (ForeignPtr addr c) (I# d) (W32# n) = IO $ \s0 ->
+    case keepAlive# c s0 (writeWord32OffAddr# addr d (extendWord32# n)) of
       s1 -> (# s1, () #)
 
 pokeWord64ForeignPtr :: ForeignPtr ty -> Int -> Word64 -> IO ()
-pokeWord64ForeignPtr fp (I# d) (W64# n) = withFP fp $ \addr s0 ->
-    case writeWord64OffAddr# addr d n s0 of
+pokeWord64ForeignPtr (ForeignPtr addr c) (I# d) (W64# n) = IO $ \s0 ->
+    case keepAlive# c s0 (writeWord64OffAddr# addr d n) of
       s1 -> (# s1, () #)
 
 pokeWordForeignPtr :: ForeignPtr ty -> Int -> Word -> IO ()
-pokeWordForeignPtr fp (I# d) (W# n) = withFP fp $ \addr s0 ->
-    case writeWord64OffAddr# addr d n s0 of
+pokeWordForeignPtr (ForeignPtr addr c) (I# d) (W# n) = IO $ \s0 ->
+    case keepAlive# c s0 (writeWordOffAddr# addr d n) of
       s1 -> (# s1, () #)
 
 pokeInt8ForeignPtr :: ForeignPtr ty -> Int -> Int8 -> IO ()
-pokeInt8ForeignPtr fp (I# d) (I8# n) = withFP fp $ \addr s0 ->
-    case writeInt8OffAddr# addr d n s0 of
+pokeInt8ForeignPtr (ForeignPtr addr c) (I# d) (I8# n) = IO $ \s0 ->
+    case keepAlive# c s0 (writeInt8OffAddr# addr d (extendInt8# n)) of
       s1 -> (# s1, () #)
 
 pokeInt16ForeignPtr :: ForeignPtr ty -> Int -> Int16 -> IO ()
-pokeInt16ForeignPtr fp (I# d) (I16# n) = withFP fp $ \addr s0 ->
-    case writeInt16OffAddr# addr d n s0 of
+pokeInt16ForeignPtr (ForeignPtr addr c) (I# d) (I16# n) = IO $ \s0 ->
+    case keepAlive# c s0 (writeInt16OffAddr# addr d (extendInt16# n)) of
       s1 -> (# s1, () #)
 
 pokeInt32ForeignPtr :: ForeignPtr ty -> Int -> Int32 -> IO ()
-pokeInt32ForeignPtr fp (I# d) (I32# n) = withFP fp $ \addr s0 ->
-    case writeInt32OffAddr# addr d n s0 of
+pokeInt32ForeignPtr (ForeignPtr addr c) (I# d) (I32# n) = IO $ \s0 ->
+    case keepAlive# c s0 (writeInt32OffAddr# addr d (extendInt32# n)) of
       s1 -> (# s1, () #)
 
 pokeInt64ForeignPtr :: ForeignPtr ty -> Int -> Int64 -> IO ()
-pokeInt64ForeignPtr fp (I# d) (I64# n) = withFP fp $ \addr s0 ->
-    case writeInt64OffAddr# addr d n s0 of
+pokeInt64ForeignPtr (ForeignPtr addr c) (I# d) (I64# n) = IO $ \s0 ->
+    case keepAlive# c s0 (writeInt64OffAddr# addr d n) of
       s1 -> (# s1, () #)
 
 pokeIntForeignPtr :: ForeignPtr ty -> Int -> Int -> IO ()
-pokeIntForeignPtr fp (I# d) (I# n) = withFP fp $ \addr s0 ->
-    case writeIntOffAddr# addr d n s0 of
+pokeIntForeignPtr (ForeignPtr addr c) (I# d) (I# n) = IO $ \s0 ->
+    case keepAlive# c s0 (writeIntOffAddr# addr d n) of
       s1 -> (# s1, () #)
 
 pokeCharForeignPtr :: ForeignPtr ty -> Int -> Char -> IO ()
-pokeCharForeignPtr fp (I# d) (C# n) = withFP fp $ \addr s0 ->
-    case writeCharOffAddr# addr d n s0 of
+pokeCharForeignPtr (ForeignPtr addr c) (I# d) (C# n) = IO $ \s0 ->
+    case keepAlive# c s0 (writeCharOffAddr# addr d n) of
       s1 -> (# s1, () #)
 


=====================================
libraries/base/GHC/IO/Buffer.hs
=====================================
@@ -73,6 +73,7 @@ import GHC.Show
 import GHC.Real
 import GHC.List
 import GHC.ForeignPtr.Ops
+import GHC.ForeignPtr  (unsafeWithForeignPtr)
 import Foreign.C.Types
 import Foreign.ForeignPtr
 import Foreign.Storable
@@ -118,17 +119,17 @@ type CharBufElem = Char
 type RawCharBuffer = RawBuffer CharBufElem
 
 peekCharBuf :: RawCharBuffer -> Int -> IO Char
-peekCharBuf arr ix = withForeignPtr arr $ \p -> do
+peekCharBuf arr ix = unsafeWithForeignPtr arr $ \p -> do
                         (c,_) <- readCharBufPtr p ix
                         return c
 
 {-# INLINE readCharBuf #-}
 readCharBuf :: RawCharBuffer -> Int -> IO (Char, Int)
-readCharBuf arr ix = withForeignPtr arr $ \p -> readCharBufPtr p ix
+readCharBuf arr ix = unsafeWithForeignPtr arr $ \p -> readCharBufPtr p ix
 
 {-# INLINE writeCharBuf #-}
 writeCharBuf :: RawCharBuffer -> Int -> Char -> IO Int
-writeCharBuf arr ix c = withForeignPtr arr $ \p -> writeCharBufPtr p ix c
+writeCharBuf arr ix c = unsafeWithForeignPtr arr $ \p -> writeCharBufPtr p ix c
 
 {-# INLINE readCharBufPtr #-}
 readCharBufPtr :: Ptr CharBufElem -> Int -> IO (Char, Int)


=====================================
libraries/bytestring
=====================================
@@ -1 +1 @@
-Subproject commit 8b5d8d0da24aefdc4d950174bf396b32335d7e0f
+Subproject commit 36c2df1feaf10fde8d5848ac47b98d6d62c4e1d7


=====================================
libraries/ghc-compact/GHC/Compact/Serialized.hs
=====================================
@@ -29,6 +29,7 @@ module GHC.Compact.Serialized(
 import GHC.Prim
 import GHC.Types
 import GHC.Word (Word8)
+import GHC.IO (unIO)
 
 import GHC.Ptr (Ptr(..), plusPtr)
 
@@ -74,12 +75,6 @@ mkBlockList buffer = compactGetFirstBlock buffer >>= go
       rest <- go next
       return $ item : rest
 
--- We MUST mark withSerializedCompact as NOINLINE
--- Otherwise the compiler will eliminate the call to touch#
--- causing the Compact# to be potentially GCed too eagerly,
--- before func had a chance to copy everything into its own
--- buffers/sockets/whatever
-
 -- | Serialize the 'Compact', and call the provided function with
 -- with the 'Compact' serialized representation.  It is not safe
 -- to return the pointer from the action and use it after
@@ -89,7 +84,6 @@ mkBlockList buffer = compactGetFirstBlock buffer >>= go
 -- unsound to use 'unsafeInterleaveIO' to lazily construct
 -- a lazy bytestring from the 'Ptr'.
 --
-{-# NOINLINE withSerializedCompact #-}
 withSerializedCompact :: Compact a ->
                          (SerializedCompact a -> IO c) -> IO c
 withSerializedCompact (Compact buffer root lock) func = withMVar lock $ \_ -> do
@@ -97,9 +91,7 @@ withSerializedCompact (Compact buffer root lock) func = withMVar lock $ \_ -> do
                     (# s', rootAddr #) -> (# s', Ptr rootAddr #) )
   blockList <- mkBlockList buffer
   let serialized = SerializedCompact blockList rootPtr
-  r <- func serialized
-  IO (\s -> case touch# buffer s of
-         s' -> (# s', r #) )
+  IO $ \s -> keepAlive# buffer s (unIO $ func serialized)
 
 fixupPointers :: Addr# -> Addr# -> State# RealWorld ->
                  (# State# RealWorld, Maybe (Compact a) #)


=====================================
testsuite/tests/ghci/should_run/T16012.script
=====================================
@@ -3,4 +3,4 @@
 -- should always return a reasonably low result.
 
 n <- System.Mem.getAllocationCounter
-if (n < 0 && n >= -160000) then putStrLn "Alloction counter in expected range" else (putStrLn $ "Unexpected allocation counter result:" ++ show n)
+if (n < 0 && n >= -200000) then putStrLn "Allocation counter in expected range" else (putStrLn $ "Unexpected allocation counter result:" ++ show n)


=====================================
testsuite/tests/ghci/should_run/T16012.stdout
=====================================
@@ -1 +1 @@
-Alloction counter in expected range
+Allocation counter in expected range


=====================================
utils/genprimopcode/Main.hs
=====================================
@@ -503,6 +503,7 @@ gen_latex_doc (Info defaults entries)
                    tvars = tvars_of typ
                    tbinds [] = ". "
                    tbinds ("o":tbs) = "(o::?) " ++ (tbinds tbs)
+                   tbinds ("p":tbs) = "(p::?) " ++ (tbinds tbs)
                    tbinds (tv:tbs) = tv ++ " " ++ (tbinds tbs)
            tvars_of (TyF t1 t2) = tvars_of t1 `union` tvars_of t2
            tvars_of (TyC t1 t2) = tvars_of t1 `union` tvars_of t2
@@ -852,6 +853,7 @@ ppTyVar "b" = "betaTyVar"
 ppTyVar "c" = "gammaTyVar"
 ppTyVar "s" = "deltaTyVar"
 ppTyVar "o" = "runtimeRep1TyVar, openAlphaTyVar"
+ppTyVar "p" = "runtimeRep2TyVar, openBetaTyVar"
 ppTyVar _   = error "Unknown type var"
 
 ppType :: Ty -> String
@@ -885,6 +887,7 @@ ppType (TyVar "b")                      = "betaTy"
 ppType (TyVar "c")                      = "gammaTy"
 ppType (TyVar "s")                      = "deltaTy"
 ppType (TyVar "o")                      = "openAlphaTy"
+ppType (TyVar "p")                      = "openBetaTy"
 
 ppType (TyApp (TyCon "State#") [x])             = "mkStatePrimTy " ++ ppType x
 ppType (TyApp (TyCon "MutVar#") [x,y])          = "mkMutVarPrimTy " ++ ppType x



View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/30c6583356d13284f470f9104d6838bb0a7a6f3b...8ae19c3ab8176ec8be5b9a5e1b441e529b814f8b

-- 
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/30c6583356d13284f470f9104d6838bb0a7a6f3b...8ae19c3ab8176ec8be5b9a5e1b441e529b814f8b
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