[Git][ghc/ghc][wip/ww-max-worker-args-old-arity] Make WorkWrap.Lib.isWorkerSmallEnough aware of the old arity
Sebastian Graf
gitlab at gitlab.haskell.org
Thu Apr 30 19:36:56 UTC 2020
Sebastian Graf pushed to branch wip/ww-max-worker-args-old-arity at Glasgow Haskell Compiler / GHC
Commits:
9e909251 by Sebastian Graf at 2020-04-30T21:36:48+02:00
Make WorkWrap.Lib.isWorkerSmallEnough aware of the old arity
We should allow a wrapper with up to 82 parameters when the original
function had 82 parameters to begin with.
I verified that this made no difference on NoFib, but then again
it doesn't use huge records...
Fixes #18122.
- - - - -
6 changed files:
- compiler/GHC/Core/Opt/SpecConstr.hs
- compiler/GHC/Core/Opt/WorkWrap/Utils.hs
- docs/users_guide/using-optimisation.rst
- + testsuite/tests/stranal/should_compile/T18122.hs
- + testsuite/tests/stranal/should_compile/T18122.stderr
- testsuite/tests/stranal/should_compile/all.T
Changes:
=====================================
compiler/GHC/Core/Opt/SpecConstr.hs
=====================================
@@ -1997,7 +1997,7 @@ callsToNewPats env fn spec_info@(SI { si_specs = done_specs }) bndr_occs calls
-- Remove ones that have too many worker variables
small_pats = filterOut too_big non_dups
- too_big (vars,_) = not (isWorkerSmallEnough (sc_dflags env) vars)
+ too_big (vars,args) = not (isWorkerSmallEnough (sc_dflags env) (length args) vars)
-- We are about to construct w/w pair in 'spec_one'.
-- Omit specialisation leading to high arity workers.
-- See Note [Limit w/w arity] in GHC.Core.Opt.WorkWrap.Utils
=====================================
compiler/GHC/Core/Opt/WorkWrap/Utils.hs
=====================================
@@ -162,7 +162,7 @@ mkWwBodies dflags fam_envs rhs_fvs fun_id demands cpr_info
wrapper_body = wrap_fn_args . wrap_fn_cpr . wrap_fn_str . applyToVars work_call_args . Var
worker_body = mkLams work_lam_args. work_fn_str . work_fn_cpr . work_fn_args
- ; if isWorkerSmallEnough dflags work_args
+ ; if isWorkerSmallEnough dflags (length demands) work_args
&& not (too_many_args_for_join_point wrap_args)
&& ((useful1 && not only_one_void_argument) || useful2)
then return (Just (worker_args_dmds, length work_call_args,
@@ -203,10 +203,13 @@ mkWwBodies dflags fam_envs rhs_fvs fun_id demands cpr_info
= False
-- See Note [Limit w/w arity]
-isWorkerSmallEnough :: DynFlags -> [Var] -> Bool
-isWorkerSmallEnough dflags vars = count isId vars <= maxWorkerArgs dflags
+isWorkerSmallEnough :: DynFlags -> Int -> [Var] -> Bool
+isWorkerSmallEnough dflags old_n_args vars
+ = count isId vars <= max old_n_args (maxWorkerArgs dflags)
-- We count only Free variables (isId) to skip Type, Kind
-- variables which have no runtime representation.
+ -- Also if the function took 82 arguments before (old_n_args), it's fine if
+ -- it takes <= 82 arguments afterwards.
{-
Note [Always do CPR w/w]
@@ -227,7 +230,8 @@ Guard against high worker arity as it generates a lot of stack traffic.
A simplified example is #11565#comment:6
Current strategy is very simple: don't perform w/w transformation at all
-if the result produces a wrapper with arity higher than -fmax-worker-args=.
+if the result produces a wrapper with arity higher than -fmax-worker-args
+and the number arguments before w/w.
It is a bit all or nothing, consider
=====================================
docs/users_guide/using-optimisation.rst
=====================================
@@ -642,14 +642,15 @@ by saying ``-fno-wombat``.
Sets the maximal number of iterations for the simplifier.
.. ghc-flag:: -fmax-worker-args=⟨n⟩
- :shortdesc: *default: 10.* If a worker has that many arguments, none will
- be unpacked anymore.
+ :shortdesc: *default: 10.* Maximum number of value arguments for a worker.
:type: dynamic
:category:
:default: 10
- If a worker has that many arguments, none will be unpacked anymore.
+ A function will not be split into worker and wrapper if the number of
+ value arguments of the resulting worker exceeds both that of the original
+ function and this setting.
.. ghc-flag:: -fno-opt-coercion
:shortdesc: Turn off the coercion optimiser
=====================================
testsuite/tests/stranal/should_compile/T18122.hs
=====================================
@@ -0,0 +1,6 @@
+{-# OPTIONS_GHC -fforce-recomp -O2 -fmax-worker-args=1 #-}
+module Lib where
+
+foo :: (Int, Int) -> Int -> Int
+foo (x, y) z = x+z
+{-# NOINLINE foo #-}
=====================================
testsuite/tests/stranal/should_compile/T18122.stderr
=====================================
@@ -0,0 +1,83 @@
+
+==================== Tidy Core ====================
+Result size of Tidy Core
+ = {terms: 35, types: 27, coercions: 0, joins: 0/0}
+
+-- RHS size: {terms: 1, types: 0, coercions: 0, joins: 0/0}
+Lib.$trModule4 :: GHC.Prim.Addr#
+[GblId,
+ Unf=Unf{Src=<vanilla>, TopLvl=True, Value=True, ConLike=True,
+ WorkFree=True, Expandable=True, Guidance=IF_ARGS [] 20 0}]
+Lib.$trModule4 = "main"#
+
+-- RHS size: {terms: 2, types: 0, coercions: 0, joins: 0/0}
+Lib.$trModule3 :: GHC.Types.TrName
+[GblId,
+ Cpr=m1,
+ Unf=Unf{Src=<vanilla>, TopLvl=True, Value=True, ConLike=True,
+ WorkFree=True, Expandable=True, Guidance=IF_ARGS [] 10 20}]
+Lib.$trModule3 = GHC.Types.TrNameS Lib.$trModule4
+
+-- RHS size: {terms: 1, types: 0, coercions: 0, joins: 0/0}
+Lib.$trModule2 :: GHC.Prim.Addr#
+[GblId,
+ Unf=Unf{Src=<vanilla>, TopLvl=True, Value=True, ConLike=True,
+ WorkFree=True, Expandable=True, Guidance=IF_ARGS [] 20 0}]
+Lib.$trModule2 = "Lib"#
+
+-- RHS size: {terms: 2, types: 0, coercions: 0, joins: 0/0}
+Lib.$trModule1 :: GHC.Types.TrName
+[GblId,
+ Cpr=m1,
+ Unf=Unf{Src=<vanilla>, TopLvl=True, Value=True, ConLike=True,
+ WorkFree=True, Expandable=True, Guidance=IF_ARGS [] 10 20}]
+Lib.$trModule1 = GHC.Types.TrNameS Lib.$trModule2
+
+-- RHS size: {terms: 3, types: 0, coercions: 0, joins: 0/0}
+Lib.$trModule :: GHC.Types.Module
+[GblId,
+ Cpr=m1,
+ Unf=Unf{Src=<vanilla>, TopLvl=True, Value=True, ConLike=True,
+ WorkFree=True, Expandable=True, Guidance=IF_ARGS [] 10 30}]
+Lib.$trModule = GHC.Types.Module Lib.$trModule3 Lib.$trModule1
+
+-- RHS size: {terms: 1, types: 0, coercions: 0, joins: 0/0}
+Lib.$wfoo [InlPrag=NOINLINE]
+ :: GHC.Prim.Int# -> GHC.Prim.Int# -> GHC.Prim.Int#
+[GblId, Arity=2, Str=<L,U><L,U>, Unf=OtherCon []]
+Lib.$wfoo = (GHC.Prim.+#)
+
+-- RHS size: {terms: 18, types: 14, coercions: 0, joins: 0/0}
+foo [InlPrag=NOUSERINLINE[0]] :: (Int, Int) -> Int -> Int
+[GblId,
+ Arity=2,
+ Str=<S(SL),1*U(1*U(U),A)><S,1*U(U)>,
+ Cpr=m1,
+ Unf=Unf{Src=InlineStable, TopLvl=True, Value=True, ConLike=True,
+ WorkFree=True, Expandable=True,
+ Guidance=ALWAYS_IF(arity=2,unsat_ok=True,boring_ok=False)
+ Tmpl= \ (w_sGZ [Occ=Once!] :: (Int, Int))
+ (w1_sH0 [Occ=Once!] :: Int) ->
+ case w_sGZ of { (ww1_sH3 [Occ=Once!], _ [Occ=Dead]) ->
+ case ww1_sH3 of { GHC.Types.I# ww4_sH6 [Occ=Once] ->
+ case w1_sH0 of { GHC.Types.I# ww6_sHc [Occ=Once] ->
+ case Lib.$wfoo ww4_sH6 ww6_sHc of ww7_sHg [Occ=Once] { __DEFAULT ->
+ GHC.Types.I# ww7_sHg
+ }
+ }
+ }
+ }}]
+foo
+ = \ (w_sGZ :: (Int, Int)) (w1_sH0 :: Int) ->
+ case w_sGZ of { (ww1_sH3, ww2_sH8) ->
+ case ww1_sH3 of { GHC.Types.I# ww4_sH6 ->
+ case w1_sH0 of { GHC.Types.I# ww6_sHc ->
+ case Lib.$wfoo ww4_sH6 ww6_sHc of ww7_sHg { __DEFAULT ->
+ GHC.Types.I# ww7_sHg
+ }
+ }
+ }
+ }
+
+
+
=====================================
testsuite/tests/stranal/should_compile/all.T
=====================================
@@ -51,3 +51,6 @@ test('T17852', [ grep_errmsg(r'\\$wf ::') ], compile, ['-ddump-worker-wrapper -
test('T16029', normal, makefile_test, [])
test('T10069', [ grep_errmsg(r'(wc1).*Int#$') ], compile, ['-dppr-cols=200 -ddump-simpl'])
+
+# We just want to find the worker of foo in there:
+test('T18122', [ grep_errmsg(r'wfoo') ], compile, ['-ddump-simpl'])
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/9e909251d187f1dadc7c1703eb5ebb3f3e737caf
--
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/9e909251d187f1dadc7c1703eb5ebb3f3e737caf
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