Incorrect code generation on x86

[aleksey]

This program prints "0" on x86 with ghc-6.10.4 and "-O" optimization at least under Linux and FreeBSD:

main = print $ pqr' 0 1

pqr' :: Int -> Int -> Integer
pqr' a b | a == b - 1 = rab
         | otherwise = ram * rmb
    where m = (a + b) `div` 2
          ram = pqr' a m
          rmb = pqr' m b
          rab = toInteger (6 * b - 5) * toInteger (2 * b - 1) *
                toInteger (6 * b - 1)

It prints the correct value "5" with either "-O0", or "-fvia-C", or on x86_64.

[igloo]

I can reproduce this with 6.10.1 but not 6.12.0.20091005, so it looks like it is already fixed.

[dmp]

I can also reproduce this with 6.10.4 but not 6.12.0.20091007 on mac os x 10.6.

[simonmar]

Test added.