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Incorrect code generation on x86

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.

Trac metadata
Trac field Value
Version 6.10.4
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture
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