[kronos29296]

I think upx is more useful for static binaries like that of Haskell applications which is kinda huge. (GHC produces huge binaries - eg. pandoc or ghc-mod). A 100 something mb binary is not what you usually have. UPX can work its magic stuff like that. More manageable not necessarily essential but when you need it you need it badly.

[DaiPlusPlus]

Is there a reason the Haskell compiler can't trim-out code it knows won't be used? Or is there another reason for the large size?

[tome]

The word on the street is that it's not unused code but rather aggressively inlined code.

[kccqzy]

That’s called split sections and it’s enabled by default in GHC 8.2.1. The main reason is aggressively inlined code compiled slightly differently.