-O0 -g slows GHC down on list literals (compared to -O0 without -g)
Tried to buld syb-0.6 testsuite with '-O0 -g' flags today and noticed compiler hung for a couple of hours.
Distilled example from syb-0.6 testsuite (exact example attached):
{-# LANGUAGE NoImplicitPrelude #-}
{-# OPTIONS_GHC -O0 #-}
module Bug (bug) where
{-# NOINLINE f #-}
f :: a -> a
f v = v
bug :: [()]
bug = f v
v :: [()]
v =
[(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),()
,(),(),(),(),() ... --- a lot of these
]
$ time ghc -c -fforce-recomp -O0 Bug.hs
real 0m0.333s
user 0m0.288s
sys 0m0.042s
$ time ghc -c -fforce-recomp -O0 -g Bug.hs
real 0m40.241s
user 0m40.021s
sys 0m0.070s
For some reason -g manages slow things down at a large factor.
Trac metadata
Trac field | Value |
---|---|
Version | 7.10.2 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |