The following Haskell funcion:

{-# LANGUAGE ForeignFunctionInterface #-}
module Main where

import Data.Word (Word32)

sum' :: Word32 -> Word32
sum' 0 = 0
sum' n = n + sum' (n-1)

foreign export javascript "sum" sum' :: Word32 -> Word32

main :: IO ()
main = print (sum' 10000000)

When compiled to WASM is quadratic on n, instead of linear, as expected. Because of that, it is millions of times slower than the native version, which isn’t expected for WASM. Is this a compiler bug, or am I doing something wrong?

I’m using GHC 9.11.20240817, with the following command:

wasm32-wasi-ghc main.hs -O2 -no-hs-main -optl-mexec-model=reactor

Followed by the post-linking step:

$(wasm32-wasi-ghc --print-libdir)/post-link.mjs -i main.wasm -o main.js

I’m then importing sum from JS and calling it on different n’s.