Incorrect optimization with Data.ByteString.append
The following program does not give the same result with -O2 and without:
import qualified Data.ByteString as B
main = let a = B.singleton 65 in print (func a a)
func y z = B.append r s
where
r = B.map (succ) x
s = B.map (succ . succ) x
x = B.append y zResult observed with GHC 7.6.1 (bytestring-0.10.0.0):
$ ghc --make test -fforce-recomp && ./test
[1 of 1] Compiling Main ( test.hs, test.o )
Linking test ...
"BBCC"
$ ghc --make test -fforce-recomp -O2 && ./test
[1 of 1] Compiling Main ( test.hs, test.o )
Linking test ...
"CCCC"Trac metadata
| Trac field | Value |
|---|---|
| Version | 7.6.1 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | libraries (other) |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | |
| Operating system | |
| Architecture |