Bartosz
Why not just cache the #datacons in the TyCon (in the DataTyCon constructor). That seems simple, direct, and fast.
And simpler than the stuff you are forced into here.
Simon
| -----Original Message-----
| From: ghc-commits [mailto:ghc-commits-bounces@haskell.org] On Behalf Of
| git@git.haskell.org
| Sent: 27 October 2017 23:03
| To: ghc-commits@haskell.org
| Subject: [commit: ghc] master: Make tagForCon non-linear (faf60e8)
|
| Repository : ssh://git@git.haskell.org/ghc
|
| On branch : master
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| >---------------------------------------------------------------
|
| commit faf60e858a293affca463043c830e1edb5685003
| Author: Bartosz Nitka
| Date: Fri Oct 20 20:30:52 2017 +0100
|
| Make tagForCon non-linear
|
| Computing the number of constructors for TyCon is linear
| in the number of constructors.
| That's wasteful if all you want to check is if that
| number is smaller than what fits in tag bits
| (usually 8 things).
|
| What this change does is to use a function that can
| determine the ineqaulity without computing the size.
|
| This improves compile time on a module with a
| data type that has 10k constructors.
| The variance in total time is (suspiciously) high,
| but going by the best of 3 the numbers are 8.186s vs 7.511s.
| For 1000 constructors the difference isn't noticeable:
| 0.646s vs 0.624s.
| The hot spots were cgDataCon and cgEnumerationTyCon
| where tagForCon is called in a loop.
|
| One alternative would be to pass down the size.
|
| Test Plan: harbormaster
|
| Reviewers: bgamari, simonmar, austin
|
| Reviewed By: simonmar
|
| Subscribers: rwbarton, thomie
|
| Differential Revision: https://phabricator.haskell.org/D4116
|
|
| >---------------------------------------------------------------
|
| faf60e858a293affca463043c830e1edb5685003
| compiler/codeGen/StgCmmClosure.hs | 11 ++++++++---
| compiler/types/TyCon.hs | 16 +++++++++++++++-
| 2 files changed, 23 insertions(+), 4 deletions(-)
|
| diff --git a/compiler/codeGen/StgCmmClosure.hs
| b/compiler/codeGen/StgCmmClosure.hs
| index 1da1f70..2501ec9 100644
| --- a/compiler/codeGen/StgCmmClosure.hs
| +++ b/compiler/codeGen/StgCmmClosure.hs
| @@ -361,13 +361,18 @@ type DynTag = Int -- The tag on a *pointer*
| isSmallFamily :: DynFlags -> Int -> Bool isSmallFamily dflags fam_size
| = fam_size <= mAX_PTR_TAG dflags
|
| +-- | Faster version of isSmallFamily if you haven't computed the size
| yet.
| +isSmallFamilyTyCon :: DynFlags -> TyCon -> Bool isSmallFamilyTyCon
| +dflags tycon =
| + tyConFamilySizeAtMost tycon (mAX_PTR_TAG dflags)
| +
| tagForCon :: DynFlags -> DataCon -> DynTag tagForCon dflags con
| - | isSmallFamily dflags fam_size = con_tag
| - | otherwise = 1
| + | isSmallFamilyTyCon dflags tycon = con_tag
| + | otherwise = 1
| where
| con_tag = dataConTag con -- NB: 1-indexed
| - fam_size = tyConFamilySize (dataConTyCon con)
| + tycon = dataConTyCon con
|
| tagForArity :: DynFlags -> RepArity -> DynTag tagForArity dflags arity
| diff --git a/compiler/types/TyCon.hs b/compiler/types/TyCon.hs index
| 39d2e9b..103c824 100644
| --- a/compiler/types/TyCon.hs
| +++ b/compiler/types/TyCon.hs
| @@ -78,7 +78,7 @@ module TyCon(
| tyConDataCons, tyConDataCons_maybe,
| tyConSingleDataCon_maybe, tyConSingleDataCon,
| tyConSingleAlgDataCon_maybe,
| - tyConFamilySize,
| + tyConFamilySize, tyConFamilySizeAtMost,
| tyConStupidTheta,
| tyConArity,
| tyConRoles,
| @@ -2205,6 +2205,20 @@ tyConFamilySize tc@(AlgTyCon { algTcRhs = rhs })
| _ -> pprPanic "tyConFamilySize 1"
| (ppr tc)
| tyConFamilySize tc = pprPanic "tyConFamilySize 2" (ppr tc)
|
| +-- | Determine if number of value constructors a 'TyCon' has is smaller
| +-- than n. Faster than tyConFamilySize tc <= n.
| +-- Panics if the 'TyCon' is not algebraic or a tuple
| +tyConFamilySizeAtMost :: TyCon -> Int -> Bool tyConFamilySizeAtMost
| +tc@(AlgTyCon { algTcRhs = rhs }) n
| + = case rhs of
| + DataTyCon { data_cons = cons } -> lengthAtMost cons n
| + NewTyCon {} -> 1 <= n
| + TupleTyCon {} -> 1 <= n
| + SumTyCon { data_cons = cons } -> lengthAtMost cons n
| + _ -> pprPanic "tyConFamilySizeAtMost
| 1"
| + (ppr tc)
| +tyConFamilySizeAtMost tc _ = pprPanic "tyConFamilySizeAtMost 2" (ppr
| +tc)
| +
| -- | Extract an 'AlgTyConRhs' with information about data constructors
| from an
| -- algebraic or tuple 'TyCon'. Panics for any other sort of 'TyCon'
| algTyConRhs :: TyCon -> AlgTyConRhs
|
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