Re: [GHC] #5767: Integer inefficiencies
#5767: Integer inefficiencies --+- Reporter: rl | Owner: igloo Type: bug | Status: new Priority: highest | Milestone: 7.4.1 Component: Compiler |Version: 7.5 Resolution: | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: Runtime performance bug | Difficulty: Unknown Testcase: | Blockedby: Blocking: |Related: --+- Changes (by PHO): * cc: pho@… (added) -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/5767#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #5767: Integer inefficiencies
#5767: Integer inefficiencies
--+-
Reporter: rl | Owner: igloo
Type: bug | Status: new
Priority: highest | Milestone: 7.4.1
Component: Compiler |Version: 7.5
Resolution: | Keywords:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: Runtime performance bug | Difficulty: Unknown
Testcase: | Blockedby:
Blocking: |Related:
--+-
Comment(by simonpj):
Note: the call to `smallInteger` arises from the `fromIntegral` method of
`Integral Int` (in `base:GHC.Real`):
{{{
instance Integral Int where
toInteger (I# i) = smallInteger i
}}}
So, yes we need a `integerToInt (smallInteger n)` RULE.
Ditto `int64ToInteger` and `wordToInteger`.
Also we'd like a RULE for `(smallInteger (I# n)`, which should generate an
`Integer` literal. This isn't easy right now for tiresome reasons. !ToDo
for 7.6. The most plausible route for doing it is to take `mkIntegerLit`
out of `Integer` literals, and keep it somewhere global instead.
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/5767#comment:7
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Re: [GHC] #5767: Integer inefficiencies
#5767: Integer inefficiencies --+- Reporter: rl | Owner: igloo Type: bug | Status: new Priority: highest | Milestone: 7.4.1 Component: Compiler |Version: 7.5 Resolution: | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: Runtime performance bug | Difficulty: Unknown Testcase: | Blockedby: Blocking: |Related: --+- Changes (by igloo): * owner: = igloo * priority: normal = highest * milestone: = 7.4.1 -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/5767#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #5767: Integer inefficiencies
#5767: Integer inefficiencies
--+-
Reporter: rl | Owner: igloo
Type: bug | Status: new
Priority: highest | Milestone: 7.4.1
Component: Compiler |Version: 7.5
Resolution: | Keywords:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: Runtime performance bug | Difficulty: Unknown
Testcase: | Blockedby:
Blocking: |Related:
--+-
Comment(by rl):
I finally found a small test case for the missing
`integerToInt/smallInteger` rule:
{{{
foo :: (Integral a, Num a) = a - a
{-# INLINE foo #-}
foo x = fromIntegral x
bar :: Int - Int
bar x = foo x
}}}
The head generates this:
{{{
foo_$sfoo =
\ (eta_B1 :: Int) -
case eta_B1 of _ { I# i_ara -
case integerToInt (smallInteger i_ara) of wild1_ard { __DEFAULT -
I# wild1_ard
}
}
bar = foo_$sfoo
}}}
Whereas 7.2.2 generates this:
{{{
bar_$sfoo = \ (eta_B1 :: Int) - eta_B1
bar = bar_$sfoo
}}}
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/5767#comment:6
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Re: [GHC] #5767: Integer inefficiencies
#5767: Integer inefficiencies
--+-
Reporter: rl | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler |Version: 7.5
Resolution: | Keywords:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: Runtime performance bug | Difficulty: Unknown
Testcase: | Blockedby:
Blocking: |Related:
--+-
Changes (by rl):
* status: closed = new
* resolution: fixed =
Comment:
I'm still seeing a regression compared to GHC 7.2.2 in this bit of Core:
{{{
case integerToInt (smallInteger a_s2jL) of wild_a1dA { __DEFAULT - f
wild_a1dA }
}}}
As I said, adding an `integerToInt/smallInteger` rule should help.
Note also that without the `INLINE` pragma on `foo`, both 7.2.2 and now
the HEAD generate this code for my original example:
{{{
bar1 :: Int
bar1 =
case GHC.Float.$w$cproperFraction @ Int GHC.Real.$fIntegralInt 51.0
of _ { (# ww1_arU, _ #) - ww1_arU }
bar :: Int - Int
bar = \ (x_a9P :: Int) - plusInt bar1 x_a9P
}}}
This isn't a regression but doesn't seem right.
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/5767#comment:4
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Re: [GHC] #5767: Integer inefficiencies
#5767: Integer inefficiencies -+-- Reporter: rl| Owner: Type: bug | Status: new Priority: normal| Milestone: Component: Compiler | Version: 7.5 Keywords:| Os: Unknown/Multiple Architecture: Unknown/Multiple | Failure: Runtime performance bug Difficulty: Unknown |Testcase: Blockedby:|Blocking: Related:| -+-- Changes (by simonpj): * difficulty: = Unknown Comment: I can see why this is. Stay tuned -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/5767#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #5767: Integer inefficiencies
#5767: Integer inefficiencies
-+--
Reporter: rl| Owner:
Type: bug | Status: merge
Priority: normal| Milestone:
Component: Compiler | Version: 7.5
Keywords:| Os: Unknown/Multiple
Architecture: Unknown/Multiple | Failure: Runtime performance bug
Difficulty: Unknown |Testcase:
Blockedby:|Blocking:
Related:|
-+--
Changes (by simonpj):
* status: new = merge
Comment:
Fixed by
{{{
commit 1074c2da93cc89cd183375ae414a18dc536a7b5d
Author: Simon Peyton Jones simo...@microsoft.com
Date: Fri Jan 13 15:46:56 2012 +
Get the knownKeyNames for doubleFromInteger right
There was a trivial typo which meant that important
newly-added rules would never fire!
compiler/prelude/PrelNames.lhs |8
1 files changed, 4 insertions(+), 4 deletions(-)
}}}
Ian, please merge; and perhaps add a test?
Simon
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/5767#comment:2
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Re: [GHC] #5767: Integer inefficiencies
#5767: Integer inefficiencies --+- Reporter: rl | Owner: Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler |Version: 7.5 Resolution: fixed| Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: Runtime performance bug | Difficulty: Unknown Testcase: | Blockedby: Blocking: |Related: --+- Changes (by igloo): * status: merge = closed * resolution: = fixed Comment: Good spot; merged as 102df6a7bc5657eef85f26d88ab6c071ec9b0b24 and I've added more cases covering this to `integerConstantFolding`. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/5767#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
[GHC] #5767: Integer inefficiencies
#5767: Integer inefficiencies
-+--
Reporter: rl | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 7.5 | Keywords:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: Runtime performance bug | Testcase:
Blockedby: | Blocking:
Related: |
-+--
Here is a small program:
{{{
module T where
foo :: RealFrac a = a - a - Int
{-# INLINE [0] foo #-}
foo x y = truncate $ (y-x)+2
module U where
import T
bar :: Int - Int
bar x = foo 1 50 + x
}}}
GHC 7.2.2 generates this optimal code:
{{{
bar = \ (x_abs :: Int) - case x_abs of _ { I# y_auX - I# (+# 51 y_auX) }
}}}
Whereas the current HEAD generates this:
{{{
bar2 :: Integer
bar2 = __integer 2
bar1 :: Int
bar1 =
case doubleFromInteger bar2
of wild_arl { __DEFAULT - I# (double2Int# (+## 49.0 wild_arl)) }
bar :: Int - Int
bar = \ (x_a9S :: Int) - plusInt bar1 x_a9S
}}}
If I remove the INLINE pragma from `foo`, the HEAD generates this:
{{{
bar1 :: Int
bar1 =
case doubleFromInteger foo1
of wild_asr { __DEFAULT -
case GHC.Float.$w$cproperFraction
@ Int GHC.Real.$fIntegralInt (+## 49.0 wild_asr)
of _ { (# ww1_as1, _ #) -
ww1_as1
}
}
bar :: Int - Int
bar = \ (x_a9W :: Int) - plusInt bar1 x_a9W
}}}
Interestingly, without the INLINE pragma 7.2.2 doesn't fare much better.
I've also seen this bit in the generated code with the HEAD but not with
7.2.2:
{{{
case integerToInt (smallInteger a_s2jL) of wild_a1dA { __DEFAULT - f
wild_a1dA }
}}}
I couldn't boil it down to a small test case yet but it leads to a
significant performance regression in at least one `vector` benchmark. I
suppose fixing this is only a matter of adding an
`integerToInt/smallInteger` rule.
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/5767
GHC http://www.haskell.org/ghc/
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