Failure to do CPR in the presence of a local letrec

Consider this code:

{-# LANGUAGE BangPatterns #-}
module NoCPR (e) where
e :: (Int, Int) -> Int -> Int -> (Int, Int)
e x y n = je x y
 where je !x y | y > 0 = x
               | otherwise = je x (y + n)

(which is adapted from #5949 (closed)).

We get this Core:

-- RHS size: {terms: 38, types: 27, coercions: 0, joins: 1/1}                
e :: (Int, Int) -> Int -> Int -> (Int, Int)                                  
[GblId,                                                                      
 Arity=3,                                                                    
 Caf=NoCafRefs,                                                              
 Str=<S,1*U(U,U)><S(S),1*U(U)><L,U(U)>m,                                     
 Unf=OtherCon []]                                                            
e = \ (x [Occ=Once!] :: (Int, Int))                                          
      (y [Occ=Once!] :: Int)                                                 
      (n [Occ=OnceL!] :: Int) ->                                             
      case x of { (ww1 [Occ=Once], ww2 [Occ=Once]) ->                        
      case y of { I# ww4 [Occ=Once] ->                                       
      joinrec {                                                              
        $wje [InlPrag=[0], Occ=LoopBreakerT[3]]                              
          :: Int -> Int -> Int# -> (Int, Int)                                
        [LclId[JoinId(3)], Arity=3, Str=<L,U><L,U><S,U>m, Unf=OtherCon []]   
        $wje (ww5 [Occ=Once*] :: Int)                                        
             (ww6 [Occ=Once*] :: Int)                                        
             (ww7 :: Int#)                                                   
          = case ># ww7 0# of {                                              
              __DEFAULT ->                                                   
                case n of { I# y1 [Occ=Once] ->                              
                case +# ww7 y1 of sat { __DEFAULT -> jump $wje ww5 ww6 sat } 
                };                                                           
              1# -> (ww5, ww6)                                               
            }; } in                                                          
      jump $wje ww1 ww2 ww4                                                  
      }                                                                      
      }                                                                      

Why is there no CPR happening for e? In fact, why is there no unboxing happening – it was for the following similar code:

e :: (Int, Int) -> Int -> (Int, Int)
e x y = x `seq` if y > 10
        then x
        else e x (y + 1)

(This is a spin-off of the dicussion at https://phabricator.haskell.org/D3811#107708).

Trac metadata

Trac field	Value
Version	8.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture