Move `backendSupportsSwitch` to `GHC.Driver.Config.Cmm`wip/move-backendSupportsSwitch

`Backend` is a CLI syntax notion `DynFlags` that shouldn't be used in
specific components, only in the translation from `DynFlags`.

-------------------------
Metric Decrease:
    T9630
-------------------------

2 files changed, 7 insertions, 10 deletions

diff --git a/compiler/GHC/Cmm/Switch.hs b/compiler/GHC/Cmm/Switch.hs
index f8c6c674ef..42b01b36e3 100644
--- a/compiler/GHC/Cmm/Switch.hs
+++ b/compiler/GHC/Cmm/Switch.hs
@@ -8,14 +8,12 @@ module GHC.Cmm.Switch (
      switchTargetsToList, eqSwitchTargetWith,
 
      SwitchPlan(..),
-     backendSupportsSwitch,
      createSwitchPlan,
   ) where
 
 import GHC.Prelude
 
 import GHC.Utils.Outputable
-import GHC.Driver.Backend
 import GHC.Utils.Panic
 import GHC.Cmm.Dataflow.Label (Label)
 
@@ -312,13 +310,6 @@ and slowed down all other cases making it not worthwhile.
 -}
 
 
--- | Does the backend support switch out of the box? Then leave this to the
--- backend!
-backendSupportsSwitch :: Backend -> Bool
-backendSupportsSwitch ViaC = True
-backendSupportsSwitch LLVM = True
-backendSupportsSwitch _    = False
-
 -- | This function creates a SwitchPlan from a SwitchTargets value, breaking it
 -- down into smaller pieces suitable for code generation.
 createSwitchPlan :: SwitchTargets -> SwitchPlan
diff --git a/compiler/GHC/Driver/Config/Cmm.hs b/compiler/GHC/Driver/Config/Cmm.hs
index 38bab62048..810ec857e0 100644
--- a/compiler/GHC/Driver/Config/Cmm.hs
+++ b/compiler/GHC/Driver/Config/Cmm.hs
@@ -3,7 +3,6 @@ module GHC.Driver.Config.Cmm
   ) where
 
 import GHC.Cmm.Config
-import GHC.Cmm.Switch (backendSupportsSwitch)
 
 import GHC.Driver.Session
 import GHC.Driver.Backend
@@ -31,3 +30,10 @@ initCmmConfig dflags = CmmConfig
           case (platformArch platform, platformOS platform, positionIndependent dflags)
           of   (ArchX86, OSDarwin, pic) -> pic
                _                        -> False
+
+-- | Does the backend support switch out of the box? Then leave this to the
+-- backend!
+backendSupportsSwitch :: Backend -> Bool
+backendSupportsSwitch ViaC = True
+backendSupportsSwitch LLVM = True
+backendSupportsSwitch _    = False