Bignum: refactor backend modules

* move backends into GHC.Num.Backend.*
* split backend selection into GHC.Num.Backend and
  GHC.Num.Backend.Selected to avoid duplication with the Check backend

7 files changed, 47 insertions, 31 deletions

diff --git a/libraries/ghc-bignum/src/GHC/Num/Backend.hs b/libraries/ghc-bignum/src/GHC/Num/Backend.hs
new file mode 100644
index 0000000000..285be2a703
--- /dev/null
+++ b/libraries/ghc-bignum/src/GHC/Num/Backend.hs
@@ -0,0 +1,15 @@
+{-# LANGUAGE CPP #-}
+{-# LANGUAGE NoImplicitPrelude #-}
+
+-- | Selected backend
+module GHC.Num.Backend
+   ( module Backend
+   )
+where
+
+#if defined(BIGNUM_CHECK)
+import GHC.Num.Backend.Check    as Backend
+#else
+import GHC.Num.Backend.Selected as Backend
+#endif
+
diff --git a/libraries/ghc-bignum/src/GHC/Num/BigNat/Check.hs b/libraries/ghc-bignum/src/GHC/Num/Backend/Check.hs
index 8431a5564d..73f8366ad0 100644
--- a/libraries/ghc-bignum/src/GHC/Num/BigNat/Check.hs
+++ b/libraries/ghc-bignum/src/GHC/Num/Backend/Check.hs
@@ -10,25 +10,17 @@
 {-# OPTIONS_GHC -Wno-name-shadowing #-}
 
 -- | Check Native implementation against another backend
-module GHC.Num.BigNat.Check where
+module GHC.Num.Backend.Check where
 
 import GHC.Prim
 import GHC.Types
 import GHC.Num.WordArray
 import GHC.Num.Primitives
-import qualified GHC.Num.BigNat.Native as Native
+import qualified GHC.Num.Backend.Native   as Native
+import qualified GHC.Num.Backend.Selected as Other
 
 #if defined(BIGNUM_NATIVE)
-#error You can't validate Native backed against itself. Choose another backend (e.g. gmp, ffi)
-
-#elif defined(BIGNUM_FFI)
-import qualified GHC.Num.BigNat.FFI as Other
-
-#elif defined(BIGNUM_GMP)
-import qualified GHC.Num.BigNat.GMP as Other
-
-#else
-#error Undefined BigNat backend. Use a flag to select it (e.g. gmp, native, ffi)`
+#error You can't validate Native backend against itself. Choose another backend (e.g. gmp, ffi)
 #endif
 
 default ()
diff --git a/libraries/ghc-bignum/src/GHC/Num/BigNat/FFI.hs b/libraries/ghc-bignum/src/GHC/Num/Backend/FFI.hs
index cfd96be7a0..a049cfe332 100644
--- a/libraries/ghc-bignum/src/GHC/Num/BigNat/FFI.hs
+++ b/libraries/ghc-bignum/src/GHC/Num/Backend/FFI.hs
@@ -13,7 +13,7 @@
 -- that replace bignat foreign calls with calls to the native platform bignat
 -- library (e.g. JavaScript's BigInt). You can also link an extra object
 -- providing the implementation.
-module GHC.Num.BigNat.FFI where
+module GHC.Num.Backend.FFI where
 
 import GHC.Prim
 import GHC.Types
diff --git a/libraries/ghc-bignum/src/GHC/Num/BigNat/GMP.hs b/libraries/ghc-bignum/src/GHC/Num/Backend/GMP.hs
index 35d3983313..a340db573e 100644
--- a/libraries/ghc-bignum/src/GHC/Num/BigNat/GMP.hs
+++ b/libraries/ghc-bignum/src/GHC/Num/Backend/GMP.hs
@@ -13,7 +13,7 @@
 --
 -- This has been adapted from the legacy `integer-gmp` package written by
 -- Herbert Valerio Riedel.
-module GHC.Num.BigNat.GMP where
+module GHC.Num.Backend.GMP where
 
 #include "MachDeps.h"
 #include "WordSize.h"
diff --git a/libraries/ghc-bignum/src/GHC/Num/BigNat/Native.hs b/libraries/ghc-bignum/src/GHC/Num/Backend/Native.hs
index 5c1baa4398..1169af41d6 100644
--- a/libraries/ghc-bignum/src/GHC/Num/BigNat/Native.hs
+++ b/libraries/ghc-bignum/src/GHC/Num/Backend/Native.hs
@@ -9,7 +9,7 @@
 {-# LANGUAGE BinaryLiterals #-}
 {-# OPTIONS_GHC -Wno-name-shadowing #-}
 
-module GHC.Num.BigNat.Native where
+module GHC.Num.Backend.Native where
 
 #include "MachDeps.h"
 #include "WordSize.h"
diff --git a/libraries/ghc-bignum/src/GHC/Num/Backend/Selected.hs b/libraries/ghc-bignum/src/GHC/Num/Backend/Selected.hs
new file mode 100644
index 0000000000..f0ffd86220
--- /dev/null
+++ b/libraries/ghc-bignum/src/GHC/Num/Backend/Selected.hs
@@ -0,0 +1,24 @@
+{-# LANGUAGE CPP #-}
+{-# LANGUAGE NoImplicitPrelude #-}
+
+-- | Selected backend
+--
+-- We need this module in addition to GHC.Num.Backend to avoid module loops with
+-- Check backend.
+module GHC.Num.Backend.Selected
+   ( module Backend
+   )
+where
+
+#if defined(BIGNUM_NATIVE)
+import GHC.Num.Backend.Native as Backend
+
+#elif defined(BIGNUM_FFI)
+import GHC.Num.Backend.FFI as Backend
+
+#elif defined(BIGNUM_GMP)
+import GHC.Num.Backend.GMP as Backend
+
+#else
+#error Undefined BigNum backend. Use a flag to select it (e.g. gmp, native, ffi)`
+#endif
diff --git a/libraries/ghc-bignum/src/GHC/Num/BigNat.hs b/libraries/ghc-bignum/src/GHC/Num/BigNat.hs
index e38c807ede..f2d9e58e17 100644
--- a/libraries/ghc-bignum/src/GHC/Num/BigNat.hs
+++ b/libraries/ghc-bignum/src/GHC/Num/BigNat.hs
@@ -23,27 +23,12 @@ import GHC.Classes
 import GHC.Magic
 import GHC.Num.Primitives
 import GHC.Num.WordArray
+import GHC.Num.Backend
 
 #if WORD_SIZE_IN_BITS < 64
 import GHC.IntWord64
 #endif
 
-#if defined(BIGNUM_CHECK)
-import GHC.Num.BigNat.Check
-
-#elif defined(BIGNUM_NATIVE)
-import GHC.Num.BigNat.Native
-
-#elif defined(BIGNUM_FFI)
-import GHC.Num.BigNat.FFI
-
-#elif defined(BIGNUM_GMP)
-import GHC.Num.BigNat.GMP
-
-#else
-#error Undefined BigNat backend. Use a flag to select it (e.g. gmp, native, ffi)`
-#endif
-
 default ()
 
 -- | A BigNat