Optimizations change result of div for Word
Here is test case
import Data.Word
main :: IO ()
main = do
print $ (maxBound :: Word) `div` 101
And result of execution
$ ghc -fforce-recomp -O2 --make reduce.hs && ./reduce
[1 of 1] Compiling Main ( reduce.hs, reduce.o )
Linking reduce ...
2891661149
@{debian:0}~/qqq/mwc $ ghc -fforce-recomp --make reduce.hs && ./reduce
[1 of 1] Compiling Main ( reduce.hs, reduce.o )
Linking reduce ...
42524428
Bug is only present on 32-bit systems. It goes away if rewrite rules are disable with -fno-enable-rewrite-rules or anything but maxBound is used as first argument or second argument is forced to be a funcion argument. So it could be bug in constant folding.
Trac metadata
Trac field | Value |
---|---|
Version | 7.6.3 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |