Inconsistent behavior of Data.Bits.shiftL with different optimization levels and -fllvm

Consider this program:

module Main (main) where

import Data.Bits
import Data.Word

main :: IO ()
main = print $ toInteger (shiftL 1 hm :: Word64)
            == toInteger (shiftL 1 hm :: Word64)

hm :: Int
hm = -1
{-# NOINLINE hm #-}

The result of this program depends greatly on what optimization levels are used, and whether -fllvm is used:

$ /opt/ghc/8.6.3/bin/ghc -fforce-recomp -O0 Bug.hs && ./Bug
[1 of 1] Compiling Main             ( Bug.hs, Bug.o )
Linking Bug ...
True

$ /opt/ghc/8.6.3/bin/ghc -fforce-recomp -O1 Bug.hs && ./Bug
[1 of 1] Compiling Main             ( Bug.hs, Bug.o )
Linking Bug ...
True

$ /opt/ghc/8.6.3/bin/ghc -fforce-recomp -O2 Bug.hs && ./Bug
[1 of 1] Compiling Main             ( Bug.hs, Bug.o )
Linking Bug ...
Bug: Bad shift length-1

$ /opt/ghc/8.6.3/bin/ghc -fforce-recomp -O0 -fllvm Bug.hs && ./Bug
[1 of 1] Compiling Main             ( Bug.hs, Bug.o )
Linking Bug ...
True

$ /opt/ghc/8.6.3/bin/ghc -fforce-recomp -O1 -fllvm Bug.hs && ./Bug
[1 of 1] Compiling Main             ( Bug.hs, Bug.o )
Linking Bug ...
False

$ /opt/ghc/8.6.3/bin/ghc -fforce-recomp -O2 -fllvm Bug.hs && ./Bug
[1 of 1] Compiling Main             ( Bug.hs, Bug.o )
Linking Bug ...
Bug: Bad shift length-1

This program manages to return all of True, False, and Bad shift length-1 depending on which flags are used!

Trac metadata

Trac field	Value
Version	8.6.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
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