Floating point with -O and -fasm is broken

I have some simple floating-point code that fails badly when you compile it with -O and -fasm on x86_64. Here is the program:

log2 x = ceiling log_x

where log_x	Double
	log_x = logBase 2 (fromIntegral (max 1 x))

vals = [1, 2, 17, 259, 1000, 10000,

2^30 + 9000, 2^31 - 1, 2^31, 2^31 + 1,

2^32 - 1, 2^32, 2^32 + 1]

main :: IO () main = putStrLn (show (map log2 vals))

The result should be: [0,1,5,9,10,14,31,31,32,32,32,32,33]

With -O and -fasm on x86_64 the last five values are corrupted (four very large numbers I'm not going to paste here, followed by 0).

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