CSE missing an easy case

Consider this Core:

case f @Int of { r1 ->
case f @Int of { r2 -> ...

There is an easy common sub-expression to be had here, which would allow to eliminate a case expression, but CSE didn't spot it in GHC 8.

Easy to fix. Here's an example that shows it

module Bug where

f g x = let r :: [a] -> [a]
            r = case g x of True  -> reverse . reverse
                            False -> reverse
        in
        r `seq` r `seq` True

Trac metadata

Trac field	Value
Version	8.0.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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