Performance regression from GHC 8.4.4 to GHC 8.6.4

Summary

Function becomes slower when compiled with latest GHC

Steps to reproduce

Here is a sample program:

{-# LANGUAGE DeriveFunctor #-}

module Main (main) where

import           Criterion.Main

data ListF a b = Cons a b
               | Nil
               deriving (Functor)

elgot :: Functor f => (f a -> a) -> (b -> Either a (f b)) -> b -> a
elgot φ ψ = h where h = either id (φ . fmap h) . ψ

collatzLength :: Integral a => a -> a
collatzLength = elgot algebra elgotCoalgebra
    where algebra Nil        = 0
          algebra (Cons _ x) = x + 1
          elgotCoalgebra 1 = Left 1
          elgotCoalgebra n
             | n `mod` 2 == 0 = Right $ Cons n (div n 2)
             | otherwise = Right $ Cons n (3 * n + 1)

main :: IO ()
main =
    defaultMain [ bgroup "collatzLength"
                      [ bench "collatzLength" $ nf collatzLength (837799 :: Int) ]
                ]

The relevant bits are in that module proper but I used criterion for benchmarks.

When run with GHC 8.6.4 I get

Benchmark elgot-bench-bench: RUNNING...
benchmarking collatzLength/collatzLength
time                 1.453 μs   (1.447 μs .. 1.460 μs)
                     1.000 R²   (1.000 R² .. 1.000 R²)
mean                 1.448 μs   (1.442 μs .. 1.456 μs)
std dev              23.46 ns   (19.43 ns .. 30.54 ns)
variance introduced by outliers: 16% (moderately inflated)

Benchmark elgot-bench-bench: FINISH

whereas with GHC 8.4.4 I get

Benchmark elgot-bench-bench: RUNNING...
benchmarking collatzLength/collatzLength
time                 1.110 μs   (1.103 μs .. 1.117 μs)
                     1.000 R²   (1.000 R² .. 1.000 R²)
mean                 1.106 μs   (1.104 μs .. 1.110 μs)
std dev              11.54 ns   (9.112 ns .. 16.53 ns)

Benchmark elgot-bench-bench: FINISH

Expected behavior

I would expect the code compiled with GHC 8.6.4 to have similar performance to the code compiled with GHC 8.4.4.

Environment

• GHC version used: GHC 8.6.4

Optional:

• Operating System: Lubuntu
• System Architecture: x86_64

(Aside: there's a darcs repo I'm using for other purposes that anyone wishing to verify may use)