Re-export GHC.Bits from GHC.Prelude with custom shift implementation.wip/andreask/unsafe-shifts

This allows us to use the unsafe shifts in non-debug builds for performance.
For older versions of base we instead export Data.Bits

See also #19618

38 files changed, 76 insertions, 53 deletions

diff --git a/compiler/GHC/Builtin/Uniques.hs b/compiler/GHC/Builtin/Uniques.hs
index 4b3f3e00b6..317670bb37 100644
--- a/compiler/GHC/Builtin/Uniques.hs
+++ b/compiler/GHC/Builtin/Uniques.hs
@@ -68,7 +68,6 @@ import GHC.Utils.Outputable
 import GHC.Utils.Misc
 import GHC.Utils.Panic
 
-import Data.Bits
 import Data.Maybe
 
 -- | Get the 'Name' associated with a known-key 'Unique'.
diff --git a/compiler/GHC/ByteCode/Asm.hs b/compiler/GHC/ByteCode/Asm.hs
index 30f2c2b633..1f11938517 100644
--- a/compiler/GHC/ByteCode/Asm.hs
+++ b/compiler/GHC/ByteCode/Asm.hs
@@ -56,7 +56,7 @@ import Data.Array.Base  ( UArray(..) )
 
 import Data.Array.Unsafe( castSTUArray )
 
-import Foreign
+import Foreign hiding (shiftL, shiftR)
 import Data.Char        ( ord )
 import Data.List        ( genericLength )
 import Data.Map.Strict (Map)
diff --git a/compiler/GHC/Cmm/CommonBlockElim.hs b/compiler/GHC/Cmm/CommonBlockElim.hs
index ffb4562c40..9ed08a2d12 100644
--- a/compiler/GHC/Cmm/CommonBlockElim.hs
+++ b/compiler/GHC/Cmm/CommonBlockElim.hs
@@ -18,7 +18,6 @@ import GHC.Cmm.Dataflow.Block
 import GHC.Cmm.Dataflow.Graph
 import GHC.Cmm.Dataflow.Label
 import GHC.Cmm.Dataflow.Collections
-import Data.Bits
 import Data.Maybe (mapMaybe)
 import qualified Data.List as List
 import Data.Word
diff --git a/compiler/GHC/Cmm/Info.hs b/compiler/GHC/Cmm/Info.hs
index eaa3c2a923..996821ab3b 100644
--- a/compiler/GHC/Cmm/Info.hs
+++ b/compiler/GHC/Cmm/Info.hs
@@ -58,7 +58,6 @@ import GHC.Utils.Misc
 import GHC.Utils.Outputable
 
 import Data.ByteString (ByteString)
-import Data.Bits
 
 -- When we split at proc points, we need an empty info table.
 mkEmptyContInfoTable :: CLabel -> CmmInfoTable
diff --git a/compiler/GHC/Cmm/LayoutStack.hs b/compiler/GHC/Cmm/LayoutStack.hs
index ac46f23f1f..2fdbb1fe5a 100644
--- a/compiler/GHC/Cmm/LayoutStack.hs
+++ b/compiler/GHC/Cmm/LayoutStack.hs
@@ -40,7 +40,6 @@ import GHC.Utils.Panic
 import qualified Data.Set as Set
 import Control.Monad.Fix
 import Data.Array as Array
-import Data.Bits
 import Data.List (nub)
 
 {- Note [Stack Layout]
diff --git a/compiler/GHC/Cmm/Opt.hs b/compiler/GHC/Cmm/Opt.hs
index f4be9520ee..6a2945c4f8 100644
--- a/compiler/GHC/Cmm/Opt.hs
+++ b/compiler/GHC/Cmm/Opt.hs
@@ -22,7 +22,6 @@ import GHC.Utils.Misc
 import GHC.Utils.Panic
 import GHC.Platform
 
-import Data.Bits
 import Data.Maybe
 
 
diff --git a/compiler/GHC/Cmm/Utils.hs b/compiler/GHC/Cmm/Utils.hs
index 3ac8b3c3ac..b42cd691f5 100644
--- a/compiler/GHC/Cmm/Utils.hs
+++ b/compiler/GHC/Cmm/Utils.hs
@@ -85,7 +85,6 @@ import GHC.Platform.Regs
 
 import Data.ByteString (ByteString)
 import qualified Data.ByteString as BS
-import Data.Bits
 import GHC.Cmm.Dataflow.Graph
 import GHC.Cmm.Dataflow.Label
 import GHC.Cmm.Dataflow.Block
diff --git a/compiler/GHC/CmmToAsm/Dwarf/Types.hs b/compiler/GHC/CmmToAsm/Dwarf/Types.hs
index cad6a63515..43d902d106 100644
--- a/compiler/GHC/CmmToAsm/Dwarf/Types.hs
+++ b/compiler/GHC/CmmToAsm/Dwarf/Types.hs
@@ -46,7 +46,6 @@ import GHC.CmmToAsm.Dwarf.Constants
 import qualified Data.ByteString as BS
 import qualified Control.Monad.Trans.State.Strict as S
 import Control.Monad (zipWithM, join)
-import Data.Bits
 import qualified Data.Map as Map
 import Data.Word
 import Data.Char
diff --git a/compiler/GHC/CmmToAsm/PPC/CodeGen.hs b/compiler/GHC/CmmToAsm/PPC/CodeGen.hs
index 0a78722c85..f1a411ab27 100644
--- a/compiler/GHC/CmmToAsm/PPC/CodeGen.hs
+++ b/compiler/GHC/CmmToAsm/PPC/CodeGen.hs
@@ -66,7 +66,6 @@ import GHC.Utils.Outputable
 import GHC.Utils.Panic
 
 import Control.Monad    ( mapAndUnzipM, when )
-import Data.Bits
 import Data.Word
 
 import GHC.Types.Basic
diff --git a/compiler/GHC/CmmToAsm/PPC/Ppr.hs b/compiler/GHC/CmmToAsm/PPC/Ppr.hs
index 5f8ab214cb..7ed13b298f 100644
--- a/compiler/GHC/CmmToAsm/PPC/Ppr.hs
+++ b/compiler/GHC/CmmToAsm/PPC/Ppr.hs
@@ -44,7 +44,6 @@ import GHC.Utils.Panic
 
 import Data.Word
 import Data.Int
-import Data.Bits
 
 -- -----------------------------------------------------------------------------
 -- Printing this stuff out
diff --git a/compiler/GHC/CmmToAsm/Ppr.hs b/compiler/GHC/CmmToAsm/Ppr.hs
index 8fba238cd1..dd656a9906 100644
--- a/compiler/GHC/CmmToAsm/Ppr.hs
+++ b/compiler/GHC/CmmToAsm/Ppr.hs
@@ -35,7 +35,6 @@ import Data.Array.ST
 import Control.Monad.ST
 
 import Data.Word
-import Data.Bits
 import Data.ByteString (ByteString)
 import qualified Data.ByteString as BS
 import GHC.Exts
diff --git a/compiler/GHC/CmmToAsm/Reg/Linear/PPC.hs b/compiler/GHC/CmmToAsm/Reg/Linear/PPC.hs
index fc9f9c0f89..e6c6015540 100644
--- a/compiler/GHC/CmmToAsm/Reg/Linear/PPC.hs
+++ b/compiler/GHC/CmmToAsm/Reg/Linear/PPC.hs
@@ -12,7 +12,6 @@ import GHC.Utils.Panic
 import GHC.Platform
 
 import Data.Word
-import Data.Bits
 
 -- The PowerPC has 32 integer and 32 floating point registers.
 -- This is 32bit PowerPC, so Word64 is inefficient - two Word32s are much
diff --git a/compiler/GHC/CmmToAsm/Reg/Linear/SPARC.hs b/compiler/GHC/CmmToAsm/Reg/Linear/SPARC.hs
index a2a0ee73f9..31e9a9dca0 100644
--- a/compiler/GHC/CmmToAsm/Reg/Linear/SPARC.hs
+++ b/compiler/GHC/CmmToAsm/Reg/Linear/SPARC.hs
@@ -15,7 +15,6 @@ import GHC.Utils.Panic
 import GHC.Platform
 
 import Data.Word
-import Data.Bits
 
 
 --------------------------------------------------------------------------------
diff --git a/compiler/GHC/CmmToAsm/Reg/Linear/X86.hs b/compiler/GHC/CmmToAsm/Reg/Linear/X86.hs
index 42f63b5752..ba9b9cc966 100644
--- a/compiler/GHC/CmmToAsm/Reg/Linear/X86.hs
+++ b/compiler/GHC/CmmToAsm/Reg/Linear/X86.hs
@@ -13,7 +13,6 @@ import GHC.Platform
 import GHC.Utils.Outputable
 
 import Data.Word
-import Data.Bits
 
 newtype FreeRegs = FreeRegs Word32
     deriving (Show,Outputable)
diff --git a/compiler/GHC/CmmToAsm/Reg/Linear/X86_64.hs b/compiler/GHC/CmmToAsm/Reg/Linear/X86_64.hs
index 44eea342a4..801b7be146 100644
--- a/compiler/GHC/CmmToAsm/Reg/Linear/X86_64.hs
+++ b/compiler/GHC/CmmToAsm/Reg/Linear/X86_64.hs
@@ -13,7 +13,6 @@ import GHC.Platform
 import GHC.Utils.Outputable
 
 import Data.Word
-import Data.Bits
 
 newtype FreeRegs = FreeRegs Word64
     deriving (Show,Outputable)
diff --git a/compiler/GHC/CmmToAsm/X86/CodeGen.hs b/compiler/GHC/CmmToAsm/X86/CodeGen.hs
index 878f3387fb..7b803b2708 100644
--- a/compiler/GHC/CmmToAsm/X86/CodeGen.hs
+++ b/compiler/GHC/CmmToAsm/X86/CodeGen.hs
@@ -86,7 +86,6 @@ import GHC.Utils.Misc
 import GHC.Types.Unique.Supply ( getUniqueM )
 
 import Control.Monad
-import Data.Bits
 import Data.Foldable (fold)
 import Data.Int
 import Data.Maybe
diff --git a/compiler/GHC/CmmToAsm/X86/Ppr.hs b/compiler/GHC/CmmToAsm/X86/Ppr.hs
index 97abf78006..2d12e90443 100644
--- a/compiler/GHC/CmmToAsm/X86/Ppr.hs
+++ b/compiler/GHC/CmmToAsm/X86/Ppr.hs
@@ -50,7 +50,6 @@ import GHC.Utils.Outputable
 import GHC.Utils.Panic
 
 import Data.Word
-import Data.Bits
 
 -- -----------------------------------------------------------------------------
 -- Printing this stuff out
diff --git a/compiler/GHC/CmmToC.hs b/compiler/GHC/CmmToC.hs
index 49f0567a81..5f6c0486bc 100644
--- a/compiler/GHC/CmmToC.hs
+++ b/compiler/GHC/CmmToC.hs
@@ -59,7 +59,6 @@ import GHC.Utils.Misc
 import Data.ByteString (ByteString)
 import qualified Data.ByteString as BS
 import Control.Monad.ST
-import Data.Bits
 import Data.Char
 import Data.List (intersperse)
 import Data.Map (Map)
diff --git a/compiler/GHC/Core/Opt/ConstantFold.hs b/compiler/GHC/Core/Opt/ConstantFold.hs
index 3a397330d7..237a87d6c4 100644
--- a/compiler/GHC/Core/Opt/ConstantFold.hs
+++ b/compiler/GHC/Core/Opt/ConstantFold.hs
@@ -76,7 +76,6 @@ import Control.Applicative ( Alternative(..) )
 
 import Control.Monad
 import Data.Functor (($>))
-import Data.Bits as Bits
 import qualified Data.ByteString as BS
 import Data.Ratio
 import Data.Word
@@ -129,9 +128,9 @@ primOpRules nm = \case
                                     , equalArgs $> Lit zeroI8 ]
    Int8NegOp   -> mkPrimOpRule nm 1 [ unaryLit negOp
                                     , semiInversePrimOp Int8NegOp ]
-   Int8SllOp   -> mkPrimOpRule nm 2 [ shiftRule LitNumInt8 (const Bits.shiftL)
+   Int8SllOp   -> mkPrimOpRule nm 2 [ shiftRule LitNumInt8 (const shiftL)
                                     , rightIdentity zeroI8 ]
-   Int8SraOp   -> mkPrimOpRule nm 2 [ shiftRule LitNumInt8 (const Bits.shiftR)
+   Int8SraOp   -> mkPrimOpRule nm 2 [ shiftRule LitNumInt8 (const shiftR)
                                     , rightIdentity zeroI8 ]
    Int8SrlOp   -> mkPrimOpRule nm 2 [ shiftRule LitNumInt8 $ const $ shiftRightLogical @Word8
                                     , rightIdentity zeroI8 ]
@@ -167,7 +166,7 @@ primOpRules nm = \case
                                     , equalArgs $> Lit zeroW8 ]
    Word8NotOp  -> mkPrimOpRule nm 1 [ unaryLit complementOp
                                     , semiInversePrimOp Word8NotOp ]
-   Word8SllOp  -> mkPrimOpRule nm 2 [ shiftRule LitNumWord (const Bits.shiftL) ]
+   Word8SllOp  -> mkPrimOpRule nm 2 [ shiftRule LitNumWord (const shiftL) ]
    Word8SrlOp  -> mkPrimOpRule nm 2 [ shiftRule LitNumWord $ const $ shiftRightLogical @Word8 ]
 
 
@@ -196,9 +195,9 @@ primOpRules nm = \case
                                     , equalArgs $> Lit zeroI16 ]
    Int16NegOp  -> mkPrimOpRule nm 1 [ unaryLit negOp
                                     , semiInversePrimOp Int16NegOp ]
-   Int16SllOp  -> mkPrimOpRule nm 2 [ shiftRule LitNumInt16 (const Bits.shiftL)
+   Int16SllOp  -> mkPrimOpRule nm 2 [ shiftRule LitNumInt16 (const shiftL)
                                     , rightIdentity zeroI16 ]
-   Int16SraOp  -> mkPrimOpRule nm 2 [ shiftRule LitNumInt16 (const Bits.shiftR)
+   Int16SraOp  -> mkPrimOpRule nm 2 [ shiftRule LitNumInt16 (const shiftR)
                                     , rightIdentity zeroI16 ]
    Int16SrlOp  -> mkPrimOpRule nm 2 [ shiftRule LitNumInt16 $ const $ shiftRightLogical @Word16
                                     , rightIdentity zeroI16 ]
@@ -234,7 +233,7 @@ primOpRules nm = \case
                                     , equalArgs $> Lit zeroW16 ]
    Word16NotOp -> mkPrimOpRule nm 1 [ unaryLit complementOp
                                     , semiInversePrimOp Word16NotOp ]
-   Word16SllOp -> mkPrimOpRule nm 2 [ shiftRule LitNumWord (const Bits.shiftL) ]
+   Word16SllOp -> mkPrimOpRule nm 2 [ shiftRule LitNumWord (const shiftL) ]
    Word16SrlOp -> mkPrimOpRule nm 2 [ shiftRule LitNumWord $ const $ shiftRightLogical @Word16 ]
 
 
@@ -263,9 +262,9 @@ primOpRules nm = \case
                                     , equalArgs $> Lit zeroI32 ]
    Int32NegOp  -> mkPrimOpRule nm 1 [ unaryLit negOp
                                     , semiInversePrimOp Int32NegOp ]
-   Int32SllOp  -> mkPrimOpRule nm 2 [ shiftRule LitNumInt32 (const Bits.shiftL)
+   Int32SllOp  -> mkPrimOpRule nm 2 [ shiftRule LitNumInt32 (const shiftL)
                                     , rightIdentity zeroI32 ]
-   Int32SraOp  -> mkPrimOpRule nm 2 [ shiftRule LitNumInt32 (const Bits.shiftR)
+   Int32SraOp  -> mkPrimOpRule nm 2 [ shiftRule LitNumInt32 (const shiftR)
                                     , rightIdentity zeroI32 ]
    Int32SrlOp  -> mkPrimOpRule nm 2 [ shiftRule LitNumInt32 $ const $ shiftRightLogical @Word32
                                     , rightIdentity zeroI32 ]
@@ -301,7 +300,7 @@ primOpRules nm = \case
                                     , equalArgs $> Lit zeroW32 ]
    Word32NotOp -> mkPrimOpRule nm 1 [ unaryLit complementOp
                                     , semiInversePrimOp Word32NotOp ]
-   Word32SllOp -> mkPrimOpRule nm 2 [ shiftRule LitNumWord (const Bits.shiftL) ]
+   Word32SllOp -> mkPrimOpRule nm 2 [ shiftRule LitNumWord (const shiftL) ]
    Word32SrlOp -> mkPrimOpRule nm 2 [ shiftRule LitNumWord $ const $ shiftRightLogical @Word32 ]
 
 
@@ -346,9 +345,9 @@ primOpRules nm = \case
                                     , semiInversePrimOp IntNotOp ]
    IntNegOp    -> mkPrimOpRule nm 1 [ unaryLit negOp
                                     , semiInversePrimOp IntNegOp ]
-   IntSllOp    -> mkPrimOpRule nm 2 [ shiftRule LitNumInt (const Bits.shiftL)
+   IntSllOp    -> mkPrimOpRule nm 2 [ shiftRule LitNumInt (const shiftL)
                                     , rightIdentityPlatform zeroi ]
-   IntSraOp    -> mkPrimOpRule nm 2 [ shiftRule LitNumInt (const Bits.shiftR)
+   IntSraOp    -> mkPrimOpRule nm 2 [ shiftRule LitNumInt (const shiftR)
                                     , rightIdentityPlatform zeroi ]
    IntSrlOp    -> mkPrimOpRule nm 2 [ shiftRule LitNumInt shiftRightLogicalNative
                                     , rightIdentityPlatform zeroi ]
@@ -389,7 +388,7 @@ primOpRules nm = \case
                                     , equalArgs >> retLit zerow ]
    WordNotOp   -> mkPrimOpRule nm 1 [ unaryLit complementOp
                                     , semiInversePrimOp WordNotOp ]
-   WordSllOp   -> mkPrimOpRule nm 2 [ shiftRule LitNumWord (const Bits.shiftL) ]
+   WordSllOp   -> mkPrimOpRule nm 2 [ shiftRule LitNumWord (const shiftL) ]
    WordSrlOp   -> mkPrimOpRule nm 2 [ shiftRule LitNumWord shiftRightLogicalNative ]
 
    -- coercions
diff --git a/compiler/GHC/CoreToStg/Prep.hs b/compiler/GHC/CoreToStg/Prep.hs
index 2e2c4d84af..74616683e3 100644
--- a/compiler/GHC/CoreToStg/Prep.hs
+++ b/compiler/GHC/CoreToStg/Prep.hs
@@ -77,7 +77,6 @@ import GHC.Types.TyThing
 import GHC.Types.CostCentre ( CostCentre, ccFromThisModule )
 import GHC.Types.Unique.Supply
 
-import Data.Bits
 import Data.List        ( unfoldr )
 import Control.Monad
 import qualified Data.Set as S
diff --git a/compiler/GHC/Data/Bitmap.hs b/compiler/GHC/Data/Bitmap.hs
index 5f6444ddc0..533dc725cd 100644
--- a/compiler/GHC/Data/Bitmap.hs
+++ b/compiler/GHC/Data/Bitmap.hs
@@ -19,7 +19,6 @@ import GHC.Prelude
 import GHC.Platform
 import GHC.Runtime.Heap.Layout
 
-import Data.Bits
 
 {-|
 A bitmap represented by a sequence of 'StgWord's on the /target/
diff --git a/compiler/GHC/Data/FastMutInt.hs b/compiler/GHC/Data/FastMutInt.hs
index e2e3a50601..3b78966577 100644
--- a/compiler/GHC/Data/FastMutInt.hs
+++ b/compiler/GHC/Data/FastMutInt.hs
@@ -15,7 +15,6 @@ module GHC.Data.FastMutInt(
 
 import GHC.Prelude
 
-import Data.Bits
 import GHC.Base
 
 data FastMutInt = FastMutInt !(MutableByteArray# RealWorld)
diff --git a/compiler/GHC/Iface/Binary.hs b/compiler/GHC/Iface/Binary.hs
index a662ebb84b..293058f0ca 100644
--- a/compiler/GHC/Iface/Binary.hs
+++ b/compiler/GHC/Iface/Binary.hs
@@ -56,7 +56,6 @@ import GHC.Utils.Misc
 import Data.Array
 import Data.Array.IO
 import Data.Array.Unsafe
-import Data.Bits
 import Data.Char
 import Data.Word
 import Data.IORef
diff --git a/compiler/GHC/Parser/CharClass.hs b/compiler/GHC/Parser/CharClass.hs
index 6d09de764c..7834109e8c 100644
--- a/compiler/GHC/Parser/CharClass.hs
+++ b/compiler/GHC/Parser/CharClass.hs
@@ -18,7 +18,6 @@ module GHC.Parser.CharClass
 
 import GHC.Prelude
 
-import Data.Bits        ( Bits((.&.),(.|.)) )
 import Data.Char        ( ord, chr )
 import Data.Word
 import GHC.Utils.Panic
diff --git a/compiler/GHC/Parser/Lexer.x b/compiler/GHC/Parser/Lexer.x
index 634cd10207..2dc8757e8d 100644
--- a/compiler/GHC/Parser/Lexer.x
+++ b/compiler/GHC/Parser/Lexer.x
@@ -77,7 +77,6 @@ import GHC.Prelude
 
 -- base
 import Control.Monad
-import Data.Bits
 import Data.Char
 import Data.List (stripPrefix, isInfixOf, partition)
 import Data.Maybe
diff --git a/compiler/GHC/Prelude.hs b/compiler/GHC/Prelude.hs
index 95c2d4b190..d538adfefb 100644
--- a/compiler/GHC/Prelude.hs
+++ b/compiler/GHC/Prelude.hs
@@ -10,15 +10,17 @@
 --   * Is compiled with -XNoImplicitPrelude
 --   * Explicitly imports GHC.Prelude
 
-module GHC.Prelude (module X) where
+module GHC.Prelude
+  (module X
+  ,module Bits
+  ,shiftL, shiftR
+  ) where
+
 
 -- We export the 'Semigroup' class but w/o the (<>) operator to avoid
 -- clashing with the (Outputable.<>) operator which is heavily used
 -- through GHC's code-base.
 
-import Prelude as X hiding ((<>))
-import Data.Foldable as X (foldl')
-
 {-
 Note [Why do we import Prelude here?]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -31,3 +33,56 @@ NoImplicitPrelude. There are two motivations for this:
     giving a smoother development experience when adding new
     extensions.
 -}
+
+import Prelude as X hiding ((<>))
+import Data.Foldable as X (foldl')
+
+#if MIN_VERSION_base(4,15,0)
+import GHC.Bits as Bits hiding (shiftL, shiftR)
+# if defined(DEBUG)
+import qualified GHC.Bits as Bits (shiftL, shiftR)
+# endif
+
+#else
+--base <4.15
+import Data.Bits as Bits hiding (shiftL, shiftR)
+# if defined(DEBUG)
+import qualified Data.Bits as Bits (shiftL, shiftR)
+# endif
+#endif
+
+{- Note [Default to unsafe shifts inside GHC]
+   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The safe shifts can introduce branches which come
+at the cost of performance. We still want the additional
+debugability for debug builds. So we define it as one or the
+other depending on the DEBUG setting.
+
+Why do we then continue on to re-export the rest of Data.Bits?
+If we would not what is likely to happen is:
+* Someone imports Data.Bits, uses xor. Things are fine.
+* They add a shift and get an ambigious definition error.
+* The are puzzled for a bit.
+* They either:
+  + Remove the import of Data.Bits and get an error because xor is not in scope.
+  + Add the hiding clause to the Data.Bits import for the shifts.
+
+Either is quite annoying. Simply re-exporting all of Data.Bits avoids this
+making for a smoother developer experience. At the cost of having a few more
+names in scope at all time. But that seems like a fair tradeoff.
+
+See also #19618
+-}
+
+-- We always want the Data.Bits method to show up for rules etc.
+{-# INLINE shiftL #-}
+{-# INLINE shiftR #-}
+shiftL, shiftR :: Bits.Bits a => a -> Int -> a
+#if defined(DEBUG)
+shiftL = Bits.shiftL
+shiftR = Bits.shiftR
+#else
+shiftL = Bits.unsafeShiftL
+shiftR = Bits.unsafeShiftR
+#endif
+
diff --git a/compiler/GHC/Runtime/Heap/Inspect.hs b/compiler/GHC/Runtime/Heap/Inspect.hs
index d6619e0e2f..d3acf5ffed 100644
--- a/compiler/GHC/Runtime/Heap/Inspect.hs
+++ b/compiler/GHC/Runtime/Heap/Inspect.hs
@@ -71,7 +71,7 @@ import Data.List ((\\))
 import GHC.Exts
 import qualified Data.Sequence as Seq
 import Data.Sequence (viewl, ViewL(..))
-import Foreign
+import Foreign hiding (shiftL, shiftR)
 import System.IO.Unsafe
 
 ---------------------------------------------
diff --git a/compiler/GHC/Runtime/Heap/Layout.hs b/compiler/GHC/Runtime/Heap/Layout.hs
index 7e4d5af136..2d402ae27a 100644
--- a/compiler/GHC/Runtime/Heap/Layout.hs
+++ b/compiler/GHC/Runtime/Heap/Layout.hs
@@ -57,7 +57,6 @@ import GHC.Utils.Outputable
 import GHC.Utils.Panic
 
 import Data.Word
-import Data.Bits
 import Data.ByteString (ByteString)
 
 {-
diff --git a/compiler/GHC/StgToByteCode.hs b/compiler/GHC/StgToByteCode.hs
index b2743ece43..0713a2e5d9 100644
--- a/compiler/GHC/StgToByteCode.hs
+++ b/compiler/GHC/StgToByteCode.hs
@@ -71,7 +71,7 @@ import GHC.Types.Tickish
 
 import Data.List ( genericReplicate, genericLength, intersperse
                  , partition, scanl', sort, sortBy, zip4, zip6, nub )
-import Foreign
+import Foreign hiding (shiftL, shiftR)
 import Control.Monad
 import Data.Char
 
diff --git a/compiler/GHC/StgToCmm/Prim.hs b/compiler/GHC/StgToCmm/Prim.hs
index fbd08b55a9..38cbd965b2 100644
--- a/compiler/GHC/StgToCmm/Prim.hs
+++ b/compiler/GHC/StgToCmm/Prim.hs
@@ -50,7 +50,6 @@ import GHC.Utils.Misc
 import GHC.Utils.Panic
 import Data.Maybe
 
-import Data.Bits ((.&.), bit)
 import Control.Monad (liftM, when, unless)
 
 ------------------------------------------------------------------------
diff --git a/compiler/GHC/SysTools/Terminal.hs b/compiler/GHC/SysTools/Terminal.hs
index c7951e0b43..fb122865f0 100644
--- a/compiler/GHC/SysTools/Terminal.hs
+++ b/compiler/GHC/SysTools/Terminal.hs
@@ -12,7 +12,7 @@ import System.Console.Terminfo (SetupTermError, Terminal, getCapability,
 import System.Posix (queryTerminal, stdError)
 #elif defined(mingw32_HOST_OS)
 import Control.Exception (catch, try)
-import Data.Bits ((.|.), (.&.))
+-- import Data.Bits ((.|.), (.&.))
 import Foreign (Ptr, peek, with)
 import qualified Graphics.Win32 as Win32
 import qualified System.Win32 as Win32
diff --git a/compiler/GHC/Types/Basic.hs b/compiler/GHC/Types/Basic.hs
index c1947fab17..bd995bdfcc 100644
--- a/compiler/GHC/Types/Basic.hs
+++ b/compiler/GHC/Types/Basic.hs
@@ -110,7 +110,6 @@ import GHC.Utils.Panic
 import GHC.Utils.Binary
 import GHC.Types.SourceText
 import Data.Data
-import Data.Bits
 import qualified Data.Semigroup as Semi
 
 {-
diff --git a/compiler/GHC/Types/Id/Info.hs b/compiler/GHC/Types/Id/Info.hs
index f9a7cacba8..399937265c 100644
--- a/compiler/GHC/Types/Id/Info.hs
+++ b/compiler/GHC/Types/Id/Info.hs
@@ -113,7 +113,6 @@ import GHC.Utils.Outputable
 import GHC.Utils.Panic
 
 import Data.Word
-import Data.Bits
 
 import GHC.StgToCmm.Types (LambdaFormInfo (..))
 
diff --git a/compiler/GHC/Types/SrcLoc.hs b/compiler/GHC/Types/SrcLoc.hs
index 1ec91017ca..f90f6df109 100644
--- a/compiler/GHC/Types/SrcLoc.hs
+++ b/compiler/GHC/Types/SrcLoc.hs
@@ -123,7 +123,6 @@ import GHC.Data.FastString
 
 import Control.DeepSeq
 import Control.Applicative (liftA2)
-import Data.Bits
 import Data.Data
 import Data.List (sortBy, intercalate)
 import Data.Function (on)
diff --git a/compiler/GHC/Types/Unique.hs b/compiler/GHC/Types/Unique.hs
index 4d19ba7f66..0735539910 100644
--- a/compiler/GHC/Types/Unique.hs
+++ b/compiler/GHC/Types/Unique.hs
@@ -59,7 +59,6 @@ import GHC.Utils.Panic
 import GHC.Exts (indexCharOffAddr#, Char(..), Int(..))
 
 import Data.Char        ( chr, ord )
-import Data.Bits
 
 {-
 ************************************************************************
diff --git a/compiler/GHC/Types/Unique/Supply.hs b/compiler/GHC/Types/Unique/Supply.hs
index 0d27bb6ceb..f3e2b4b353 100644
--- a/compiler/GHC/Types/Unique/Supply.hs
+++ b/compiler/GHC/Types/Unique/Supply.hs
@@ -39,7 +39,6 @@ import GHC.IO
 
 import GHC.Utils.Monad
 import Control.Monad
-import Data.Bits
 import Data.Char
 import GHC.Exts( Ptr(..), noDuplicate#, oneShot )
 #if MIN_VERSION_GLASGOW_HASKELL(9,1,0,0)
diff --git a/compiler/GHC/Utils/Binary.hs b/compiler/GHC/Utils/Binary.hs
index daddd0ce0f..37b303a3cd 100644
--- a/compiler/GHC/Utils/Binary.hs
+++ b/compiler/GHC/Utils/Binary.hs
@@ -85,7 +85,7 @@ import GHC.Utils.Fingerprint
 import GHC.Types.SrcLoc
 
 import Control.DeepSeq
-import Foreign
+import Foreign hiding (shiftL, shiftR)
 import Data.Array
 import Data.Array.IO
 import Data.Array.Unsafe
diff --git a/compiler/GHC/Utils/Misc.hs b/compiler/GHC/Utils/Misc.hs
index 96dce36f94..bc3f580db8 100644
--- a/compiler/GHC/Utils/Misc.hs
+++ b/compiler/GHC/Utils/Misc.hs
@@ -160,7 +160,6 @@ import Data.Char        ( isUpper, isAlphaNum, isSpace, chr, ord, isDigit, toUpp
 import Data.Int
 import Data.Ratio       ( (%) )
 import Data.Ord         ( comparing )
-import Data.Bits
 import Data.Word
 import qualified Data.IntMap as IM
 import qualified Data.Set as Set