#5284: Simplifier performance regression (or infinite loop)
---------------------------------+------------------------------------------
Reporter: simonmar | Owner:
Type: bug | Status: new
Priority: highest | Milestone: 7.2.1
Component: Compiler | Version: 7.0.3
Keywords: | Testcase:
Blockedby: | Difficulty:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: Compile-time performance bug
---------------------------------+------------------------------------------
Comment(by simonpj):
That's odd. It seems ok now. Can you try again?
{{{
bash$ wc T3016.hs
584 3486 174956 T3016.hs
bash$ time ~/builds/validate-HEAD/inplace/bin/ghc-stage2 -c -O T3016.hs
-fforce-recomp +RTS -s
13,862,317,264 bytes allocated in the heap
8,584,884,064 bytes copied during GC
123,304,256 bytes maximum residency (54 sample(s))
2,311,912 bytes maximum slop
325 MB total memory in use (0 MB lost due to fragmentation)
Tot time (elapsed) Avg pause Max
pause
Gen 0 26462 colls, 0 par 12.39s 12.40s 0.0005s
0.0113s
Gen 1 54 colls, 0 par 9.54s 9.55s 0.1769s
0.6452s
Parallel GC work balance: -nan (0 / 0, ideal 1)
MUT time (elapsed) GC time (elapsed)
Task 0 (worker) : 0.00s ( 41.86s) 0.00s ( 0.00s)
Task 1 (worker) : 0.00s ( 41.86s) 0.00s ( 0.00s)
Task 2 (bound) : 16.94s ( 19.91s) 21.92s ( 21.95s)
SPARKS: 0 (0 converted, 0 dud, 0 GC'd, 0 fizzled)
INIT time 0.00s ( 0.00s elapsed)
MUT time 16.94s ( 19.90s elapsed)
GC time 21.93s ( 21.95s elapsed)
EXIT time 0.00s ( 0.00s elapsed)
Total time 38.87s ( 41.86s elapsed)
Alloc rate 818,245,673 bytes per MUT second
Productivity 43.6% of total user, 40.5% of total elapsed
gc_alloc_block_sync: 0
whitehole_spin: 0
gen[0].sync: 0
gen[1].sync: 0
real 0m41.927s
user 0m40.970s
sys 0m0.920s
}}}
It's not great, though. The module is about 600 lines of code with two
very big integer constants on each line. These are all re-expressed as
products of reasonable-sized integers. So just one line of the file
expands to the code below.
This is a bit stupid. We should just have a function
{{{
mkInteger :: [Int] -> Integer
mkInteger xs = go 1 xs
where
go :: Integer -> [Int] -> Integer
go acc [] = acc
go acc (x:xs) = go (acc*maxInt + x) xs
}}}
and then convert big `Integer` literals into `mkInteger [p,q,r]` where the
`[p,q,r]` are the coefficients. That would generate far less code.
Small literals should use the old route, so that constant folding has a
chance of happening.
Would anyone like to do this? The relevant code is in
`MkCore.mkIntegerExpr`.
{{{
a_s7Y0 :: T3016.P
[LclId,
Str=DmdType,
Unf=Unf{Src=<vanilla>, TopLvl=True, Arity=0, Value=False,
ConLike=False, Cheap=False, Expandable=False, Guidance=NEVER}]
a_s7Y0 =
case GHC.Integer.plusInteger
(GHC.Integer.Type.S# 790894860564361520)
(GHC.Integer.timesInteger
(GHC.Integer.plusInteger
(GHC.Integer.Type.S# 5694277513942979484)
(GHC.Integer.timesInteger
(GHC.Integer.plusInteger
(GHC.Integer.Type.S# 8695760837991935493)
(GHC.Integer.timesInteger
(GHC.Integer.plusInteger
(GHC.Integer.Type.S# 3111745589992438195)
(GHC.Integer.timesInteger
(GHC.Integer.plusInteger
(GHC.Integer.Type.S# 5932496986262705997)
(GHC.Integer.timesInteger
(GHC.Integer.plusInteger
(GHC.Integer.Type.S#
2467237890019628039)
(GHC.Integer.timesInteger
(GHC.Integer.plusInteger
(GHC.Integer.Type.S#
728563175101493569)
(GHC.Integer.timesInteger
(GHC.Integer.plusInteger
(GHC.Integer.Type.S#
6858788324311301629)
(GHC.Integer.timesInteger
(GHC.Integer.Type.S#
2273139894617598453)
(GHC.Integer.Type.S#
9223372036854775807)))
(GHC.Integer.Type.S#
9223372036854775807)))
(GHC.Integer.Type.S#
9223372036854775807)))
(GHC.Integer.Type.S#
9223372036854775807)))
(GHC.Integer.Type.S# 9223372036854775807)))
(GHC.Integer.Type.S# 9223372036854775807)))
(GHC.Integer.Type.S# 9223372036854775807)))
(GHC.Integer.Type.S# 9223372036854775807))
of nt_s80m [Dmd=Just L] { __DEFAULT ->
case GHC.Integer.plusInteger
(GHC.Integer.Type.S# 1951866921918820082)
(GHC.Integer.timesInteger
(GHC.Integer.plusInteger
(GHC.Integer.Type.S# 455876676931171453)
(GHC.Integer.timesInteger
(GHC.Integer.plusInteger
(GHC.Integer.Type.S# 1769193696036972708)
(GHC.Integer.timesInteger
(GHC.Integer.plusInteger
(GHC.Integer.Type.S# 2753606951986561079)
(GHC.Integer.timesInteger
(GHC.Integer.plusInteger
(GHC.Integer.Type.S# 2915216215365162184)
(GHC.Integer.timesInteger
(GHC.Integer.plusInteger
(GHC.Integer.Type.S#
1817063239677662611)
(GHC.Integer.timesInteger
(GHC.Integer.plusInteger
(GHC.Integer.Type.S#
5655233183732864)
(GHC.Integer.timesInteger
(GHC.Integer.plusInteger
(GHC.Integer.Type.S#
8781166386102664098)
(GHC.Integer.timesInteger
(GHC.Integer.plusInteger
(GHC.Integer.Type.S# 5376807536228193618)
(GHC.Integer.timesInteger
(GHC.Integer.Type.S# 8)
(GHC.Integer.Type.S#
9223372036854775807)))
(GHC.Integer.Type.S#
9223372036854775807)))
(GHC.Integer.Type.S#
9223372036854775807)))
(GHC.Integer.Type.S#
9223372036854775807)))
(GHC.Integer.Type.S#
9223372036854775807)))
(GHC.Integer.Type.S# 9223372036854775807)))
(GHC.Integer.Type.S# 9223372036854775807)))
(GHC.Integer.Type.S# 9223372036854775807)))
(GHC.Integer.Type.S# 9223372036854775807))
of nt_s80o [Dmd=Just L] { __DEFAULT ->
T3016.NZ
(nt_s80m
`cast` (Sym (T3016.NTCo:F) :: GHC.Integer.Type.Integer ~ T3016.F))
(nt_s80o
`cast` (Sym (T3016.NTCo:F) :: GHC.Integer.Type.Integer ~ T3016.F))
}
}
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5284#comment:1>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
_______________________________________________
Glasgow-haskell-bugs mailing list
[email protected]
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
