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Opened by JohnWiegley@trac-JohnWiegley
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Strange slowness when using async library with FFI callbacks

I've attached a Haskell and a C file, when compiled as such:

ghc -DSPEED_BUG=0 -threaded -O2 -main-is SpeedTest SpeedTest.hs SpeedTestC.c

You should find that with 7.4.2, 7.6.3 or a recent build of 7.8, building with SPEED_BUG=0 produces an executable that takes more than a second to run, while building with SPEED_BUG=1 runs very quickly. I've also attached the Core for both scenarios.

Edited by Herbert Valerio Riedel