Commit 3d2991f8 authored by Ben Gamari's avatar Ben Gamari 🐢 Committed by Marge Bot

simplifier: Kill off ufKeenessFactor

We used to have another factor, ufKeenessFactor, which would scale the
discounts before they were subtracted from the size. This was justified
with the following comment:

  -- We multiple the raw discounts (args_discount and result_discount)
  -- ty opt_UnfoldingKeenessFactor because the former have to do with
  --  *size* whereas the discounts imply that there's some extra
  --  *efficiency* to be gained (e.g. beta reductions, case reductions)
  -- by inlining.

However, this is highly suspect since it means that we subtract a
*scaled* size from an absolute size, resulting in crazy (e.g. negative)
scores in some cases (#15304). We consequently killed off
ufKeenessFactor and bumped up the ufUseThreshold to compensate.

Adjustment of unfolding use threshold
=====================================

Since this removes a discount from our inlining heuristic, I revisited our
default choice of -funfolding-use-threshold to minimize the change in
overall inlining behavior. Specifically, I measured runtime allocations
and executable size of nofib and the testsuite performance tests built
using compilers (and core libraries) built with several values of
-funfolding-use-threshold.

This comes as a result of a quantitative comparison of testsuite
performance and code size as a function of ufUseThreshold, comparing
GHC trees using values of 50, 60, 70, 80, 90, and 100. The test set
consisted of nofib and the testsuite performance tests.
A full summary of these measurements are found in the description of
!2608

Comparing executable sizes (relative to the base commit) across all
nofib tests, we see that sizes are similar to the baseline:

            gmean      min      max   median
thresh
50         -6.36%   -7.04%   -4.82%   -6.46%
60         -5.04%   -5.97%   -3.83%   -5.11%
70         -2.90%   -3.84%   -2.31%   -2.92%
80         -0.75%   -2.16%   -0.42%   -0.73%
90         +0.24%   -0.41%   +0.55%   +0.26%
100        +1.36%   +0.80%   +1.64%   +1.37%
baseline   +0.00%   +0.00%   +0.00%   +0.00%

Likewise, looking at runtime allocations we see that 80 gives slightly
better optimisation than the baseline:

            gmean      min      max   median
thresh
50         +0.16%   -0.16%   +4.43%   +0.00%
60         +0.09%   -0.00%   +3.10%   +0.00%
70         +0.04%   -0.09%   +2.29%   +0.00%
80         +0.02%   -1.17%   +2.29%   +0.00%
90         -0.02%   -2.59%   +1.86%   +0.00%
100        +0.00%   -2.59%   +7.51%   -0.00%
baseline   +0.00%   +0.00%   +0.00%   +0.00%

Finally, I had to add a NOINLINE in T4306 to ensure that `upd` is
worker-wrappered as the test expects. This makes me wonder whether the
inlining heuristic is now too liberal as `upd` is quite a large
function. The same measure was taken in T12600.

             Wall clock time compiling Cabal with -O0
thresh       50     60     70     80     90      100    baseline
build-Cabal  93.88  89.58  92.59  90.09  100.26  94.81  89.13

Also, this change happens to avoid the spurious test output in
`plugin-recomp-change` and `plugin-recomp-change-prof` (see #17308).

Metric Decrease:
    hie002
    T12234
    T13035
    T13719
    T14683
    T4801
    T5631
    T5642
    T9020
    T9872d
    T9961
Metric Increase:
    T12150
    T12425
    T13701
    T14697
    T15426
    T1969
    T3064
    T5837
    T6048
    T9203
    T9872a
    T9872b
    T9872c
    T9872d
    haddock.Cabal
    haddock.base
    haddock.compiler
parent bcd66859
Pipeline #17761 passed with stages
in 406 minutes and 8 seconds
......@@ -1002,10 +1002,6 @@ ufUseThreshold
At a call site, if the unfolding, less discounts, is smaller than
this, then it's small enough inline
ufKeenessFactor
Factor by which the discounts are multiplied before
subtracting from size
ufDictDiscount
The discount for each occurrence of a dictionary argument
as an argument of a class method. Should be pretty small
......@@ -1024,6 +1020,22 @@ ufVeryAggressive
loop breakers.
Historical Note: Before April 2020 we had another factor,
ufKeenessFactor, which would scale the discounts before they were subtracted
from the size. This was justified with the following comment:
-- We multiply the raw discounts (args_discount and result_discount)
-- ty opt_UnfoldingKeenessFactor because the former have to do with
-- *size* whereas the discounts imply that there's some extra
-- *efficiency* to be gained (e.g. beta reductions, case reductions)
-- by inlining.
However, this is highly suspect since it means that we subtract a *scaled* size
from an absolute size, resulting in crazy (e.g. negative) scores in some cases
(#15304). We consequently killed off ufKeenessFactor and bumped up the
ufUseThreshold to compensate.
Note [Function applications]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In a function application (f a b)
......@@ -1307,8 +1319,7 @@ tryUnfolding dflags id lone_variable
extra_doc = text "discounted size =" <+> int discounted_size
discounted_size = size - discount
small_enough = discounted_size <= ufUseThreshold dflags
discount = computeDiscount dflags arg_discounts
res_discount arg_infos cont_info
discount = computeDiscount arg_discounts res_discount arg_infos cont_info
where
mk_doc some_benefit extra_doc yes_or_no
......@@ -1553,14 +1564,9 @@ which Roman did.
-}
computeDiscount :: DynFlags -> [Int] -> Int -> [ArgSummary] -> CallCtxt
computeDiscount :: [Int] -> Int -> [ArgSummary] -> CallCtxt
-> Int
computeDiscount dflags arg_discounts res_discount arg_infos cont_info
-- We multiple the raw discounts (args_discount and result_discount)
-- ty opt_UnfoldingKeenessFactor because the former have to do with
-- *size* whereas the discounts imply that there's some extra
-- *efficiency* to be gained (e.g. beta reductions, case reductions)
-- by inlining.
computeDiscount arg_discounts res_discount arg_infos cont_info
= 10 -- Discount of 10 because the result replaces the call
-- so we count 10 for the function itself
......@@ -1569,8 +1575,7 @@ computeDiscount dflags arg_discounts res_discount arg_infos cont_info
-- Discount of 10 for each arg supplied,
-- because the result replaces the call
+ round (ufKeenessFactor dflags *
fromIntegral (total_arg_discount + res_discount'))
+ total_arg_discount + res_discount'
where
actual_arg_discounts = zipWith mk_arg_discount arg_discounts arg_infos
total_arg_discount = sum actual_arg_discounts
......
......@@ -699,7 +699,6 @@ data DynFlags = DynFlags {
ufUseThreshold :: Int,
ufFunAppDiscount :: Int,
ufDictDiscount :: Int,
ufKeenessFactor :: Float,
ufDearOp :: Int,
ufVeryAggressive :: Bool,
......@@ -1430,12 +1429,11 @@ defaultDynFlags mySettings llvmConfig =
-- into Csg.calc (The unfolding for sqr never makes it into the
-- interface file.)
ufCreationThreshold = 750,
ufUseThreshold = 60,
ufUseThreshold = 80,
ufFunAppDiscount = 60,
-- Be fairly keen to inline a function if that means
-- we'll be able to pick the right method from a dictionary
ufDictDiscount = 30,
ufKeenessFactor = 1.5,
ufDearOp = 40,
ufVeryAggressive = False,
......@@ -3023,8 +3021,9 @@ dynamic_flags_deps = [
(intSuffix (\n d -> d {ufFunAppDiscount = n}))
, make_ord_flag defFlag "funfolding-dict-discount"
(intSuffix (\n d -> d {ufDictDiscount = n}))
, make_ord_flag defFlag "funfolding-keeness-factor"
(floatSuffix (\n d -> d {ufKeenessFactor = n}))
, make_dep_flag defFlag "funfolding-keeness-factor"
(floatSuffix (\_ d -> d))
"-funfolding-keeness-factor is no longer respected as of GHC 8.12"
, make_ord_flag defFlag "fmax-worker-args"
(intSuffix (\n d -> d {maxWorkerArgs = n}))
, make_ord_flag defGhciFlag "fghci-hist-size"
......
......@@ -12,4 +12,4 @@ Simplifier ticks exhausted
simplifier non-termination has been judged acceptable.
To see detailed counts use -ddump-simpl-stats
Total ticks: 140082
Total ticks: 140084
......@@ -75,7 +75,8 @@ test('break015', expect_broken(1532), ghci_script, ['break015.script'])
test('break016', combined_output, ghci_script, ['break016.script'])
test('break017', [extra_files(['../QSort.hs']),
combined_output], ghci_script, ['break017.script'])
test('break018', extra_files(['../mdo.hs']), ghci_script, ['break018.script'])
test('break018', [expect_broken(18004), extra_files(['../mdo.hs'])],
ghci_script, ['break018.script'])
test('break019', extra_files(['../Test2.hs']), ghci_script, ['break019.script'])
test('break020', extra_files(['Break020b.hs']), ghci_script, ['break020.script'])
test('break021', extra_files(['Break020b.hs', 'break020.hs']), ghci_script, ['break021.script'])
......
......@@ -41,7 +41,7 @@ _result :: IO () = _
^^^^^^^^^^^^^^^^^
13 in_another_module 0
Stopped in Main.in_another_decl, break020.hs:(6,21)-(7,30)
_result :: m () = _
_result :: IO () = _
5
vv
6 in_another_decl _ = do line1 0
......@@ -49,7 +49,7 @@ _result :: m () = _
^^
8
Stopped in Main.in_another_decl, break020.hs:6:24-30
_result :: m () = _
_result :: IO () = _
5
6 in_another_decl _ = do line1 0
^^^^^^^
......@@ -61,7 +61,7 @@ _result :: IO () = _
^^^^^^^^^
4 line2 _ = return ()
Stopped in Main.in_another_decl, break020.hs:7:24-30
_result :: m () = _
_result :: IO () = _
6 in_another_decl _ = do line1 0
7 line2 0
^^^^^^^
......
......@@ -64,80 +64,34 @@ Rule fired: Class op $p1Monad (BUILTIN)
Rule fired: Class op pure (BUILTIN)
Rule fired: ># (BUILTIN)
Rule fired: ==# (BUILTIN)
Rule fired: Class op >>= (BUILTIN)
Rule fired: Class op >>= (BUILTIN)
Rule fired: Class op $p1Monad (BUILTIN)
Rule fired: Class op $p1Applicative (BUILTIN)
Rule fired: SPEC/Main $fApplicativeStateT @Identity _ (Main)
Rule fired: SPEC/Main $fMonadStateT_$c>>= @Identity _ (Main)
Rule fired: SPEC/Main $fMonadStateT_$c>> @Identity _ (Main)
Rule fired: Class op return (BUILTIN)
Rule fired: Class op <*> (BUILTIN)
Rule fired: Class op $p1Monad (BUILTIN)
Rule fired: Class op $p1Applicative (BUILTIN)
Rule fired: SPEC/Main $fApplicativeStateT @Identity _ (Main)
Rule fired: SPEC/Main $fMonadStateT_$c>>= @Identity _ (Main)
Rule fired: SPEC/Main $fMonadStateT_$c>> @Identity _ (Main)
Rule fired: Class op return (BUILTIN)
Rule fired: Class op >>= (BUILTIN)
Rule fired: Class op >>= (BUILTIN)
Rule fired: Class op >>= (BUILTIN)
Rule fired: Class op >>= (BUILTIN)
Rule fired: Class op $p1Monad (BUILTIN)
Rule fired: Class op $p1Applicative (BUILTIN)
Rule fired: SPEC/Main $fApplicativeStateT @Identity _ (Main)
Rule fired: Class op $p1Monad (BUILTIN)
Rule fired: Class op $p1Applicative (BUILTIN)
Rule fired: SPEC/Main $fApplicativeStateT @Identity _ (Main)
Rule fired: Class op pure (BUILTIN)
Rule fired: Class op $p1Monad (BUILTIN)
Rule fired: Class op $p1Applicative (BUILTIN)
Rule fired: SPEC/Main $fMonadStateT_$c>>= @Identity _ (Main)
Rule fired: SPEC/Main $fApplicativeStateT_$c<*> @Identity _ (Main)
Rule fired: SPEC/Main $fApplicativeStateT_$cpure @Identity _ (Main)
Rule fired: SPEC/Main $fFunctorStateT @Identity _ (Main)
Rule fired: SPEC/Main $fFunctorStateT_$cfmap @Identity _ (Main)
Rule fired: Class op fmap (BUILTIN)
Rule fired: SPEC/Main $fFunctorStateT_$cfmap @Identity _ (Main)
Rule fired: Class op fmap (BUILTIN)
Rule fired: Class op fmap (BUILTIN)
Rule fired: Class op fmap (BUILTIN)
Rule fired: SPEC/Main $fFunctorStateT_$cfmap @Identity _ (Main)
Rule fired: Class op fmap (BUILTIN)
Rule fired: SPEC/Main $fFunctorStateT_$cfmap @Identity _ (Main)
Rule fired: Class op fmap (BUILTIN)
Rule fired: Class op return (BUILTIN)
Rule fired: Class op return (BUILTIN)
Rule fired: Class op >>= (BUILTIN)
Rule fired: Class op >>= (BUILTIN)
Rule fired: Class op return (BUILTIN)
Rule fired: Class op >>= (BUILTIN)
Rule fired: Class op >>= (BUILTIN)
Rule fired: Class op return (BUILTIN)
Rule fired: Class op fmap (BUILTIN)
Rule fired: Class op fmap (BUILTIN)
Rule fired: Class op >>= (BUILTIN)
Rule fired: Class op >>= (BUILTIN)
Rule fired: Class op fmap (BUILTIN)
Rule fired: SPEC/Main $fFunctorStateT @Identity _ (Main)
Rule fired: SPEC/Main $fApplicativeStateT_$cpure @Identity _ (Main)
Rule fired: SPEC/Main $fApplicativeStateT_$c<*> @Identity _ (Main)
Rule fired: Class op fmap (BUILTIN)
Rule fired: SPEC/Main $fApplicativeStateT_$c*> @Identity _ (Main)
Rule fired: Class op fmap (BUILTIN)
Rule fired: SPEC/Main $fFunctorStateT @Identity _ (Main)
Rule fired: SPEC/Main $fApplicativeStateT_$cpure @Identity _ (Main)
Rule fired: SPEC/Main $fApplicativeStateT_$c<*> @Identity _ (Main)
Rule fired: SPEC/Main $fApplicativeStateT_$c*> @Identity _ (Main)
Rule fired: SPEC/Main $fMonadStateT @Identity _ (Main)
Rule fired: Class op $p1Monad (BUILTIN)
Rule fired: Class op $p1Applicative (BUILTIN)
Rule fired: Class op fmap (BUILTIN)
Rule fired: Class op $p1Monad (BUILTIN)
Rule fired: Class op <*> (BUILTIN)
Rule fired: Class op $p1Monad (BUILTIN)
Rule fired: Class op $p1Applicative (BUILTIN)
Rule fired: Class op fmap (BUILTIN)
Rule fired: Class op $p1Monad (BUILTIN)
Rule fired: Class op <*> (BUILTIN)
Rule fired: Class op $p1Monad (BUILTIN)
Rule fired: Class op $p1Applicative (BUILTIN)
Rule fired: Class op fmap (BUILTIN)
Rule fired: Class op >>= (BUILTIN)
Rule fired: SPEC go @(StateT (Sum Int) Identity) (Main)
Rule fired: Class op $p1Monad (BUILTIN)
Rule fired: Class op pure (BUILTIN)
Rule fired: SPEC/Main $fMonadStateT @Identity _ (Main)
Rule fired: SPEC go @(StateT (Sum Int) Identity) (Main)
Rule fired: Class op return (BUILTIN)
......@@ -167,7 +167,6 @@ test('plugin-recomp-flags',
test('plugin-recomp-change',
[extra_files(['plugin-recomp/', 'plugin-recomp-test.hs']),
only_ways([config.ghc_plugin_way]),
when(compiler_debugged(), expect_broken_for(17308, ['dyn'])),
pre_cmd('$MAKE -s --no-print-directory -C plugin-recomp package.plugins01 TOP={top}')
],
makefile_test, [])
......@@ -175,7 +174,6 @@ test('plugin-recomp-change',
test('plugin-recomp-change-prof',
[extra_files(['plugin-recomp/', 'plugin-recomp-test.hs']),
only_ways([config.ghc_plugin_way]),
when(compiler_debugged(), expect_broken_for(17308, ['dyn'])),
pre_cmd('$MAKE -s --no-print-directory -C plugin-recomp package.plugins01 TOP={top}'),
when(not config.have_profiling,skip)
],
......
......@@ -27,3 +27,4 @@ instance (Eq1 f) => Eq1 (G f) where
foo :: G F Int -> G F Int -> Bool
foo a b = eq1 a b
{-# NOINLINE foo #-}
Rule fired: Class op - (BUILTIN)
Rule fired: Class op + (BUILTIN)
Rule fired: Class op + (BUILTIN)
Rule fired: Class op enumFromTo (BUILTIN)
Rule fired: Class op foldr (BUILTIN)
Rule fired: Class op foldr (BUILTIN)
Rule fired: +# (BUILTIN)
Rule fired: Class op foldr (BUILTIN)
Rule fired: Class op enumFromTo (BUILTIN)
Rule fired: fold/build (GHC.Base)
RULES: "SPEC $cm @()" [0]
RULES: "SPEC f @Bool @() @(Maybe Integer)" [0]
"SPEC/T17966 $fShowMaybe_$cshow @Integer"
"SPEC/T17966 $fShowMaybe_$cshowList @Integer"
"SPEC/T17966 $fShowMaybe @Integer"
......@@ -10,3 +10,4 @@ upd (UPD _ (D x _)) = sqrt $! (x*x + x*x + sin x + x*x + x*x + cos x + x*x + x*x
x*x + x*x + sin x + x*x + x*x + cos x + x*x + x*x + tan x +
x*x + x*x + sin x + x*x + x*x + cos x + x*x + x*x + tan x)
-- make the rhs large enough to be worker/wrapperred
{-# NOINLINE upd #-}
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