import UniqSupply ( uniqFromSupply, uniqsFromSupply, splitUniqSupply,
UniqSupply )
import CmdLineOpts ( opt_OutputLanguage, opt_EmitCExternDecls )
-import Maybes ( maybeToBool )
import PrimOp ( PrimOp(..), CCall(..), isDynamicTarget )
import Panic ( panic )
+import Maybe ( isJust )
+
infixr 9 `thenFlt`
\end{code}
mkAlgAltsCSwitch :: CAddrMode -> [(ConTag, AbstractC)] -> AbstractC -> AbstractC
mkAlgAltsCSwitch scrutinee tagged_alts deflt_absc
- = CSwitch scrutinee (adjust tagged_alts) deflt_absc
+ | isJust (nonemptyAbsC deflt_absc)
+ = CSwitch scrutinee (adjust tagged_alts) deflt_absc
+ | otherwise
+ = CSwitch scrutinee (adjust rest) first_alt
where
+ -- it's ok to convert one of the alts into a default if we don't already have
+ -- one, because this is an algebraic case and we're guaranteed that the tag
+ -- will match one of the branches.
+ ((tag,first_alt):rest) = tagged_alts
+
-- Adjust the tags in the switch to start at zero.
-- This is the convention used by primitive ops which return algebraic
-- data types. Why? Because for two-constructor types, zero is faster