On Windows, enabling any plugin drastically worsens compilation time

Summary

On Windows, enabling a GHC plugin in any module increases compilation time by about a minute, regardless of how much is being recompiled - as long as one of the recompiled modules requires the plugin. Aside from that, this added time seems to be independent of how many modules require the plugin.

This appears to be a regression introduced in GHC 9.4.8 (it does not happen in GHC 9.4.7).

Steps to reproduce

Main.hs:

{-# OPTIONS_GHC -fplugin=Test #-}
module Main where

main :: IO ()
main = putStrLn "Hi"

Test.hs:

module Test where

import GHC.Driver.Plugins

plugin :: Plugin
plugin = defaultPlugin

In WSL, recompiling yields this (I had to enable -dynamic for it to work):

[user@Legion plugin-test]$ time ghc Main.hs -dynamic -package ghc
[2 of 3] Compiling Main             ( Main.hs, Main.o ) [Impure plugin forced recompilation]
[3 of 3] Linking Main [Objects changed]

real    0m1.943s
user    0m0.939s
sys     0m0.318s

In Windows, recompiling yields this:

$ time ghc Main.hs -package ghc
[2 of 3] Compiling Main             ( Main.hs, Main.o ) [Impure plugin forced recompilation]
[3 of 3] Linking Main.exe [Objects changed]

real    0m57.003s
user    0m0.000s
sys     0m0.000s

If the -fplugin line in Main.hs is removed, this is the result on Windows instead:

$ time ghc Main.hs -package ghc
[1 of 2] Compiling Main             ( Main.hs, Main.o ) [Source file changed]
[2 of 2] Linking Main.exe [Objects changed]

real    0m0.900s
user    0m0.000s
sys     0m0.000s

Expected behavior

The compilation time should not differ significantly between Windows and Linux/WSL.

Environment

• GHC version used: 9.8.1, 9.6.3, 9.4.8

Optional:

• Operating System: Windows 11 (and Arch on WSL)
• System Architecture: x86_64