ghc-prim

GHC primitives

Version on this page:0.10.0
LTS Haskell 22.29:0.10.0
Stackage Nightly 2024-07-20:0.11.0
Latest on Hackage:0.11.0

See all snapshots ghc-prim appears in

BSD-3-Clause licensed
Maintained by [email protected]
This version can be pinned in stack with:ghc-prim-0.10.0@sha256:9d268988ee93289b0938b9b07edcbe25d212049e853d867be39f8dfb8f41d108,2968

This package contains the primitive types and operations supplied by GHC. It is an internal package, only for the use of GHC developers. GHC users should not use it! If you do use it then expect breaking changes at any time without warning. You should prefer to import GHC.Exts from the base package instead.

Changes

0.10.0

  • Shipped with GHC 9.6.1

  • The listThreads# primop was added, allowing the user to enumerate all threads (running and blocked) in the program:

    listThreads# :: State# RealWorld -> (# State# RealWorld, Array# ThreadId# #)
    
  • The type of the labelThread# primop was changed from:

    labelThread# :: ThreadId# -> Addr# -> State# RealWorld -> State# RealWorld
    

    to

    labelThread# :: ThreadId# -> ByteArray# -> State# RealWorld -> State# RealWorld
    

    Where the ByteArray# must contain a UTF-8-encoded string.

  • The threadLabel# primop was added, allowing the user to query the label of a given ThreadId#.

  • isByteArrayPinned# now only considers an array pinned if it was explicitly pinned by the user. This is required to avoid ghc issue #22255 which showed that the old behaviour could cause segfaults when used in combination with compact regions. We are working on ways to allow users and library authors to get back the performance benefits of the old behaviour where possible.

0.9.0 August 2022

  • Shipped with GHC 9.4.1

  • magicDict has been renamed to withDict and is now defined in GHC.Magic.Dict instead of GHC.Prim. withDict now has the type:

    withDict :: forall {rr :: RuntimeRep} st dt (r :: TYPE rr). st -> (dt => r) -> r
    

    Unlike magicDict, withDict can be used without defining an intermediate data type. For example, the withTypeable function from the Data.Typeable module can now be defined as:

    withTypeable :: forall k (a :: k) rep (r :: TYPE rep). ()
                 => TypeRep a -> (Typeable a => r) -> r
    withTypeable rep k = withDict @(TypeRep a) @(Typeable a) rep k
    

    Note that the explicit type applications are required, as the call to withDict would be ambiguous otherwise.

  • Primitive types and functions which handle boxed values are now levity-polymorphic, meaning that they now also work with unlifted boxed values (i.e. values whose type has kind TYPE (BoxedRep Unlifted)).

    The following type constructors are now levity-polymorphic:

    • Array#, SmallArray#, Weak#, StablePtr#, StableName#,

    • MutableArray#, SmallMutableArray#, MutVar#, TVar#, MVar#, IOPort#.

    For example, Array# used to have kind:

    Type -> UnliftedType
    

    but it now has kind:

    forall {l :: Levity}. TYPE (BoxedRep l) -> UnliftedType
    

    Similarly, MutVar# used to have kind:

    Type -> Type -> UnliftedType
    

    but it now has kind:

    forall {l :: Levity}. Type -> TYPE (BoxedRep l) -> UnliftedType
    

    This means that in Array# a, MutableArray# s a, MutVar# s a, …, the element type a, must always be boxed, but it can now either be lifted or unlifted. In particular, arrays and mutable variables can now be used to store other arrays and mutable variables.

    All functions which use these updated primitive types are also levity-polymorphic:

    • all array operations (reading/writing/copying/…), for both arrays and small arrays, mutable and immutable:

      • newArray#, readArray#, writeArray#, sizeofArray#, sizeofMutableArray#, indexArray#, unsafeFreezeArray#, unsafeThawArray#, copyArray#, copyMutableArray#, cloneArray#, cloneMutableArray#, freezeArray#, thawArray#, casArray#,

      • newSmallArray#, shrinkSmallMutableArray#, readSmallArray#, writeSmallArray#, sizeofSmallArray#, getSizeofSmallMutableArray#, indexSmallArray#, unsafeFreezeSmallArray#, unsafeThawSmallArray#, copySmallArray#, copySmallMutableArray#, cloneSmallArray#, cloneSmallMutableArray#, freezeSmallArray#, thawSmallArray#, casSmallArray#,

    • newMutVar#, readMutVar#, writeMutVar#,casMutVar#,

    • operations on MVar# and TVar#:

      • newTVar#, readTVar#, readTVarIO#, writeTVar#,

      • newMVar#, takeMVar#, tryTakeMVar#, putMVar#, tryPutMVar#, readMVar#, tryReadMVar#,

    • STM operations atomically#, retry#, catchRetry# and catchSTM#.

    • newIOPort#, readIOPort#, writeIOPort#,

    • mkWeak#, mkWeakNoFinalizer#, addCFinalizerToWeak#, deRefWeak#, finalizeWeak#,

    • makeStablePtr#, deRefStablePtr#, eqStablePtr#, makeStableName#, stableNameToInt#,

    For example, the full type of newMutVar# is now:

    newMutVar#
      :: forall {l :: Levity} s (a :: TYPE (BoxedRep l)).
         a -> State# s -> (# State# s, MVar# s a #)
    

    and the full type of writeSmallArray# is:

    writeSmallArray#
      :: forall {l :: Levity} s (a :: TYPE ('BoxedRep l)).
         SmallMutableArray# s a -> Int# -> a -> State# s -> State# s
    
  • ArrayArray# and MutableArrayArray# have been moved from GHC.Prim to GHC.Exts. They are deprecated, because their functionality is now subsumed by Array# and MutableArray#.

  • mkWeak#, mkWeakNoFinalizer#, touch# and keepAlive# are now levity-polymorphic instead of representation-polymorphic. For instance:

    mkWeakNoFinalizer#
      :: forall {l :: Levity} {k :: Levity}
                (a :: TYPE ('BoxedRep l))
                (b :: TYPE ('BoxedRep k)).
         a -> b -> State# RealWorld -> (# State# RealWorld, Weak# b #)
    

    That is, the type signature now quantifies over the Levity of a instead of its RuntimeRep. In addition, this variable is now inferred, instead of specified, meaning that it is no longer eligible for visible type application. Note that b is now also levity-polymorphic, due to the change outlined in the previous point.

  • Primitive functions for throwing and catching exceptions are now more polymorphic than before. For example, catch# now has type:

    catch#
      :: forall {r :: RuntimeRep} {l :: Levity}
                (a :: TYPE r)
                (b :: TYPE ('BoxedRep l)).
          ( State# RealWorld -> (# State# RealWorld, a #) )
      -> ( b -> State# RealWorld -> (# State# RealWorld, a #) )
      -> State# RealWorld -> (# State# RealWorld, a #)
    

    The following functions are concerned:

    • catch#,

    • raise#, raiseIO#,

    • maskAsyncExceptions#, maskUninterruptible#, unmaskAsyncExceptions#.

    Note in particular that raise# is now both representation-polymorphic (with an inferred RuntimeRep argument) and levity-polymorphic, with type:

    raise# :: forall {l :: Levity} {r :: RuntimeRep}
                     (a :: TYPE (BoxedRep l))
                     (b :: TYPE r).
              a -> b
    
  • fork# and forkOn# are now representation-polymorphic. For example, fork# now has type: ::

    fork# :: forall {r :: RuntimeRep} (a :: TYPE r).
             (State# RealWorld -> (# State# RealWorld, a #))
          -> (State# RealWorld -> (# State# RealWorld, a #))
    
  • reallyUnsafePtrEquality# has been made more general, as it is now both levity-polymorphic and heterogeneous:

    reallyUnsafePtrEquality#
      :: forall {l :: Levity} {k :: Levity}
                (a :: TYPE (BoxedRep l))
                (b :: TYPE (BoxedRep k))
      . a -> b -> Int#
    

    This means that reallyUnsafePtrEquality# can be used on primitive arrays such as Array# and ByteArray#. It can also be used on values of different types, without needing to call unsafeCoerce#.

  • The following functions have been moved from GHC.Prim to GHC.Exts:

    • sameMutableArray#, sameSmallMutableArray#, sameMutableByteArray# and sameMutableArrayArray#,
    • sameMutVar#, sameTVar# andsameMVar#,
    • sameIOPort#,
    • eqStableName#.
  • The following functions have been added to GHC.Exts:

    sameArray# :: Array# a -> Array# a -> Int#
    sameSmallArray# :: SmallArray# a -> SmallArray# a -> Int#
    sameByteArray# :: ByteArray# -> ByteArray# -> Int#
    sameArrayArray# :: ArrayArray# -> ArrayArray# -> Int#
    

0.8.0

  • Change array access primops to use type with size maxing the element size:

    • index{Int,Word}<N>Array# :: ByteArray# -> Int# -> {Int,Word}<N>#
    • indexWord8ArrayAs{Int,Word}<N># :: ByteArray# -> Int# -> {Int,Word}<N>#
    • read{Int,Word}<N>Array# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, {Int,Word}<N># #)
    • write{Int,Word}<N>Array# :: MutableByteArray# s -> Int# -> {Int,Word}<N># -> State# s -> State# s
    • readWord8ArrayAs{Int,Word}<N># :: MutableByteArray# s -> Int# -> State# s -> (# State# s, {Int,Word}<N># #)
    • writeWord8ArrayAs{Int,Word}<N># :: MutableByteArray# s -> Int# -> {Int,Word}<N># -> State# s -> State# s

    This was already the for the 64-bit access primops, but not the smaller ones.

  • Rename some numeric prim type conversion primops:

    • extend{Int,Word}<N># -> extend<N>To{Int,Word}#
    • narrow{Int,Word}<N># -> intTo{Int,Word}<N>#
  • Add primops for atomic compare and swap for sizes other that wordsize:

    casInt8Array# :: MutableByteArray# s -> Int# -> Int8# -> Int8# -> State# s -> (# State# s, Int8# #) casInt16Array# :: MutableByteArray# s -> Int# -> Int16# -> Int16# -> State# s -> (# State# s, Int16# #) casInt32Array# :: MutableByteArray# s -> Int# -> Int32# -> Int32# -> State# s -> (# State# s, Int32# #) casInt64Array# :: MutableByteArray# s -> Int# -> Int64# -> Int64# -> State# s -> (# State# s, Int64# #) atomicCasWord8Addr# :: Addr# -> Word8# -> Word8# -> State# s -> (# State# s, Word8# #) atomicCasWord16Addr# :: Addr# -> Word16# -> Word16# -> State# s -> (# State# s, Word16# #) atomicCasWord32Addr# :: Addr# -> Word32# -> Word32# -> State# s -> (# State# s, Word32# #) atomicCasWord64Addr# :: Addr# -> WORD64 -> WORD64 -> State# s -> (# State# s, WORD64 #)

0.7.0

  • Shipped with GHC 9.0.1

  • Add known-key cstringLength# to GHC.CString. This is just the C function strlen, but a built-in rewrite rule allows GHC to compute the result at compile time when the argument is known.

  • In order to support unicode better the following functions in GHC.CString gained UTF8 counterparts:

      unpackAppendCStringUtf8# :: Addr# -> [Char] -> [Char]
      unpackFoldrCStringUtf8# :: Addr# -> (Char -> a -> a) -> a -> a
    
  • unpackFoldrCString* variants can now inline in phase [0].

    If the folding function is known this allows for unboxing of the Char argument resulting in much faster code.

  • Renamed the singleton tuple GHC.Tuple.Unit to GHC.Tuple.Solo.

  • Add primops for atomic exchange:

      atomicExchangeAddrAddr# :: Addr# -> Addr# -> State# s -> (# State# s, Addr# #)
      atomicExchangeWordAddr# :: Addr# -> Word# -> State# s -> (# State# s, Word# #)
    
  • Add primops for atomic compare and swap at a given Addr#:

      atomicCasAddrAddr# :: Addr# -> Addr# -> Addr# -> State# s -> (# State# s, Addr# #)
      atomicCasWordAddr# :: Addr# -> Word# -> Word# -> State# s -> (# State# s, Word# #)
    
  • Add an explicit fixity for (~) and (~~):

      infix 4 ~, ~~
    
  • Introduce keepAlive# to replace touch# in controlling object lifetime without the soundness issues of the latter (see #17760).

0.6.1

  • Shipped with GHC 8.10.1

  • Add primop for shrinking SmallMutableArray# to GHC.Prim:

      shrinkSmallMutableArray# :: SmallMutableArray# s a -> Int# -> State# s -> State# s
    

    Note that resizeSmallMutableArray# is not included as as primitive. It has been implemented in library space in GHC.Exts. See the release notes of base.

  • Added to GHC.Prim:

      closureSize# :: a -> Int#
    
  • Added to GHC.Prim:

      bitReverse# :: Word# -> Word#
      bitReverse8# :: Word# -> Word#
      bitReverse16# :: Word# -> Word#
      bitReverse32# :: Word# -> Word#
      bitReverse64# :: Word# -> Word#
    

    bitReverse# is a primop that, for a Word of 8, 16, 32 or 64 bits, reverses the order of its bits e.g. 0b110001 becomes 0b100011. These primitives use optimized machine instructions when available.

  • Add Int# multiplication primop:

    timesInt2# :: Int# -> Int# -> (# Int#, Int#, Int# #)
    

    timesInt2# computes the multiplication of its two parameters and returns a triple (isHighNeeded,high,low) where high and low are respectively the high and low bits of the double-word result. isHighNeeded is a cheap way to test if the high word is a sign-extension of the low word (isHighNeeded = 0#) or not (isHighNeeded = 1#).

0.6.0

  • Shipped with GHC 8.8.1

  • Added to GHC.Prim:

      traceBinaryEvent# :: Addr# -> Int# -> State# s -> State# s
    

0.5.3

  • Shipped with GHC 8.6.1

  • Added to GHC.Prim:

      addWordC# :: Word# -> Word# -> (# Word#, Int# #)
    
  • unpackClosure# can now unpack any valid Haskell closure. Previously it returned empty pointer and non-pointer arrays for thunks.

  • Add unaligned bytearray access primops (#4442)

       readWord8ArrayAsChar# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, Char# #)
       readWord8ArrayAsAddr# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, Addr# #)
       readWord8ArrayAsFloat# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, Float# #)
       readWord8ArrayAsDouble# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, Double# #)
       readWord8ArrayAsStablePtr# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, StablePtr# #)
       readWord8ArrayAsInt16# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, Int16# #)
       readWord8ArrayAsInt32# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, Int32# #)
       readWord8ArrayAsInt64# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, Int64# #)
       readWord8ArrayAsInt# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, Int# #)
    
       readWord8ArrayAsWord16# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, Word16# #)
       readWord8ArrayAsWord32# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, Word32# #)
       readWord8ArrayAsWord64# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, Word64# #)
       readWord8ArrayAsWord# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, Word# #)
    
       writeWord8ArrayAsChar# :: MutableByteArray# s -> Int# -> Char# -> State# s -> State# s
       writeWord8ArrayAsAddr# :: MutableByteArray# s -> Int# -> Addr# -> State# s -> State# s
       writeWord8ArrayAsFloat# :: MutableByteArray# s -> Int# -> Float# -> State# s -> State# s
       writeWord8ArrayAsDouble# :: MutableByteArray# s -> Int# -> Double# -> State# s -> State# s
       writeWord8ArrayAsStablePtr# :: MutableByteArray# s -> Int# -> StablePtr# -> State# s -> State# s
    
       writeWord8ArrayAsInt16# :: MutableByteArray# s -> Int# -> Int16# -> State# s -> State# s
       writeWord8ArrayAsInt32# :: MutableByteArray# s -> Int# -> Int32# -> State# s -> State# s
       writeWord8ArrayAsInt64# :: MutableByteArray# s -> Int# -> Int64# -> State# s -> State# s
       writeWord8ArrayAsInt# :: MutableByteArray# s -> Int# -> Int# -> State# s -> State# s
    
       writeWord8ArrayAsWord16# :: MutableByteArray# s -> Int# -> Word16# -> State# s -> State# s
       writeWord8ArrayAsWord32# :: MutableByteArray# s -> Int# -> Word32# -> State# s -> State# s
       writeWord8ArrayAsWord64# :: MutableByteArray# s -> Int# -> Word64# -> State# s -> State# s
       writeWord8ArrayAsWord# :: MutableByteArray# s -> Int# -> Word# -> State# s -> State# s
    

0.5.2.0

  • Shipped with GHC 8.4.1

  • Added to GHC.Prim:

      compareByteArrays# :: ByteArray# -> Int# -> ByteArray# -> Int# -> Int# -> Int#
    
  • Don’t allocate a thunk for each unpacked UTF-8 character in unpackCStringUtf8#

0.5.1.1 November 2017

  • Shipped with GHC 8.2.2

  • Changed strictness properties of catchRetry# (#14171)

0.5.1.0 July 2017

  • Shipped with GHC 8.2.1

  • Added to GHC.Prim:

      fabsDouble# :: Double# -> Double#
      fabsFloat# :: Float# -> Float#
      isByteArrayPinned# :: ByteArray# -> Int#
      isMutableByteArrayPinned# :: MutableByteArray# s -> Int#
      anyToAddr# :: a -> State# (RealWorld) -> (# State# (RealWorld),Addr# #)
    
  • New primitives for compact regions in GHC.Prim:

      Compact#
      compactNew#
      compactResize#
      compactContains#
      compactContainsAny#
      compactGetFirstBlock#
      compactGetNextBlock#
      compactAllocateBlock#
      compactFixupPointers#
      compactAdd#
      compactAddWithSharing#
      compactSize#
    
  • Generalised noDuplicate# from

      noDuplicate# :: State# (RealWorld) -> State# (RealWorld)
    

    to

      noDuplicate# :: State# s -> State# s
    

0.5.0.0

  • Shipped with GHC 8.0.1

  • GHC.Classes: new class IP (a :: Symbol) b | a -> b

  • GHC.Prim: changed type signatures from

      check# :: (State# RealWorld -> (# State# RealWorld, a #)) -> State# RealWorld -> (# State# RealWorld, () #)
      finalizeWeak# :: Weak# a -> State# RealWorld -> (# State# RealWorld, Int#, State# RealWorld -> (# State# RealWorld, () #) #)
      mkWeak# :: a -> b -> c -> State# RealWorld -> (# State# RealWorld, Weak# b #)
    

    to

      check# :: (State# RealWorld -> (# State# RealWorld, a #)) -> State# RealWorld -> State# RealWorld
      finalizeWeak# :: Weak# a -> State# RealWorld -> (# State# RealWorld, Int#, State# RealWorld -> (# State# RealWorld, b #) #)
      mkWeak# :: a -> b -> (State# RealWorld -> (# State# RealWorld, c #)) -> State# RealWorld -> (# State# RealWorld, Weak# b #)
    
  • Removed from GHC.Prim:

      parAt# :: b -> a -> Int# -> Int# -> Int# -> Int# -> c -> Int#
      parAtAbs# :: a -> Int# -> Int# -> Int# -> Int# -> Int# -> b -> Int#
      parAtForNow# :: b -> a -> Int# -> Int# -> Int# -> Int# -> c -> Int#
      parAtRel# :: a -> Int# -> Int# -> Int# -> Int# -> Int# -> b -> Int#
      parGlobal# :: a -> Int# -> Int# -> Int# -> Int# -> b -> Int#
      parLocal# :: a -> Int# -> Int# -> Int# -> Int# -> b -> Int#
    
  • Added to GHC.Prim:

      getSizeofMutableByteArray# :: MutableByteArray# d -> State# d -> (# State# d, Int# #)
      subWordC# :: Word# -> Word# -> (# Word#, Int# #)
      runRW# :: (State# RealWorld -> (# State# RealWorld, o #)) -> (# State# RealWorld, o #)
    
  • Added to GHC.Types:

      data Module = Module TrName TrName
      data Nat
      data Symbol
      data TrName = TrNameS Addr# | TrNameD [Char]
      data TyCon = TyCon Word# Word# Module TrName