Native Code gen miscompiles double2Int# / float2Int# on x86_32
Brad Clow: I upgraded from GHC 6.6.1 to 6.8.1 and around that time I noticed that the output from an app I am working on changed. I have distilled the code down to the following example that produces different output depending on whether it is compiled with -O2 or not:
main = do
let (T x) = read "T 3"
print $ f x
print $ g x
data T = T Int deriving (Read, Show)
f x = truncate $ 2000 / fromIntegral ((x * 25) + 10)
g :: Int -> Int
g x = f x(See http://www.haskell.org/pipermail/haskell-cafe/2007-November/034930.html)
The reason is that the code generated for double2Int# by the native code generator does not round correctly. (It's not 100% predictable, I believe, but it'll usually round.)
Trac metadata
| Trac field | Value |
|---|---|
| Version | 6.8.1 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Compiler |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | |
| Operating system | Unknown |
| Architecture |