-O/-O2 causes program to run too slow

[David Spies]

I have a program I wrote to submit for the Car Game problem on Kattis:
https://open.kattis.com/problems/cargame
but it runs over the 5-second time-limit

I downloaded the test data and found that on GHC 7.8.3, if I switch from
-O2 to -O0, it runs three times faster (almost certainly fast enough for
Kattis to accept).  Can someone tell me what's going on?  Is this a bug?
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