Superfluous seq no eliminated
Program:
foo :: Int -> Int
foo 0 = 0
foo n = (if n < 5 then 1 else 2) `seq` foo (n-1)GHC generates this code:
T.$wfoo =
\ (ww_slm :: GHC.Prim.Int#) ->
case ww_slm of ds_XkE {
__DEFAULT ->
case case GHC.Prim.<# ds_XkE 5 of _ {
GHC.Bool.False -> lvl1_rlG; GHC.Bool.True -> lvl_rlE
}
of _ { __DEFAULT ->
T.$wfoo (GHC.Prim.-# ds_XkE 1)
};
0 -> 0
}Note that the seq is still there although it is a nop. This actually occurs in stream fusion code.
Trac metadata
| Trac field | Value |
|---|---|
| Version | 6.13 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Compiler |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | |
| Operating system | |
| Architecture |