Simon Jakobi pushed to branch wip/sjakobi/T27296-stable-simpl at Glasgow Haskell Compiler / GHC

Commits:

12 changed files:

Changes:

  • changelog.d/stable-core-dump-order-27296
    1 
    +section: compiler
    2 
    +synopsis: Add :ghc-flag:`-dstable-core-dump-order` to print top-level Core bindings in a stable, source-location-based order that does not depend on uniques, making Core dumps easier to diff.
    3 
    +issues: #27296
    4 
    +mrs: !16143

  • compiler/GHC/Core/Lint.hs
    ... ... @@ -327,12 +327,17 @@ dumpPassResult logger dump_core_sizes name_ppr_ctx mb_flag hdr extra_info binds
    327 327 
       where
    328 328 
         size_doc = sep [text "Result size of" <+> text hdr, nest 2 (equals <+> ppr (coreBindsStats binds))]
    329 329
    330 
    +    -- See Note [Stable Core dump order] in GHC.Core.Ppr
    331 
    +    binds' | sdocStableCoreDumpOrder (log_default_dump_context (logFlags logger))
    332 
    +                        = sortCoreBindingsForDump binds
    333 
    +           | otherwise  = binds
    334 
    +
    330 335 
         dump_doc  = vcat [ nest 2 extra_info
    331 336 
                          , size_doc
    332 337 
                          , blankLine
    333 338 
                          , if dump_core_sizes
    334 
    -                        then pprCoreBindingsWithSize binds
    335 
    -                        else pprCoreBindings         binds
    339 
    +                        then pprCoreBindingsWithSize binds'
    340 
    +                        else pprCoreBindings         binds'
    336 341 
                          , ppUnless (null rules) pp_rules ]
    337 342 
         pp_rules = vcat [ blankLine
    338 343 
                         , text "------ Local rules for imported ids --------"

  • compiler/GHC/Core/Ppr.hs
    ... ... @@ -19,6 +19,7 @@ module GHC.Core.Ppr (
    19 19 
             pprCoreExpr, pprParendExpr,
    20 20 
             pprCoreBinding, pprCoreBindings, pprCoreAlt,
    21 21 
             pprCoreBindingWithSize, pprCoreBindingsWithSize,
    22 
    +        sortCoreBindingsForDump,
    22 23 
             pprCoreBinder, pprCoreBinders, pprId, pprIds,
    23 24 
             pprRule, pprRules, pprOptCo,
    24 25 
             pprOcc, pprOccWithTick
    ... ... @@ -30,7 +31,7 @@ import GHC.Core
    30 31 
     import GHC.Core.Stats (exprStats)
    31 32 
     import GHC.Types.Fixity (LexicalFixity(..))
    32 33 
     import GHC.Types.Literal( pprLiteral )
    33 
    -import GHC.Types.Name( pprInfixName, pprPrefixName )
    34 
    +import GHC.Types.Name( pprInfixName, pprPrefixName, getOccString, getSrcSpan )
    34 35 
     import GHC.Types.Var
    35 36 
     import GHC.Types.Id
    36 37 
     import GHC.Types.Id.Info
    ... ... @@ -44,9 +45,13 @@ import GHC.Core.Coercion
    44 45 
     import GHC.Types.Basic
    45 46 
     import GHC.Utils.Misc
    46 47 
     import GHC.Utils.Outputable
    47 
    -import GHC.Types.SrcLoc ( pprUserRealSpan )
    48 
    +import GHC.Utils.Panic (panic)
    49 
    +import GHC.Types.SrcLoc ( SrcSpan(..), srcSpanStartLine, srcSpanStartCol
    50 
    +                        , pprUserRealSpan )
    48 51 
     import GHC.Types.Tickish
    49 52
    53 
    +import Data.List ( sortOn )
    54 
    +
    50 55 
     {-
    51 56 
     ************************************************************************
    52 57 
     *                                                                      *
    ... ... @@ -71,6 +76,70 @@ pprCoreBindingWithSize :: CoreBind -> SDoc
    71 76 
     pprCoreBindingsWithSize = pprTopBinds sizeAnn
    72 77 
     pprCoreBindingWithSize = pprTopBind sizeAnn
    73 78
    79 
    +{- Note [Stable Core dump order]
    80 
    +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    81 
    +The order of top-level bindings in a Core dump (-ddump-simpl etc.) is the
    82 
    +compiler's internal processing order, which is sensitive to Uniques. Uniques
    83 
    +can shift whenever an unrelated upstream module changes, so the bindings get
    84 
    +re-ordered and a textual diff of two dumps fails to line up the real changes
    85 
    +(#27296).
    86 
    +
    87 
    +With -dstable-core-dump-order we reorder the top-level bindings at dump time into
    88 
    +a stable, diffable order. 'sortCoreBindingsForDump' sorts by a key that is
    89 
    +*independent of Uniques* (so the output is diffable even without
    90 
    +-dsuppress-uniques):
    91 
    +
    92 
    +  1. the binder's source span (real spans in source order; noSrcSpan last).
    93 
    +     Workers and specialisations inherit their origin's source span (see
    94 
    +     'mkWorkerId' and 'newSpecIdSM'), so they cluster next to the binding they
    95 
    +     come from.
    96 
    +  2. a "$-rank" so that within one source span the compiler-derived binders sort
    97 
    +     *before* the origin they come from (e.g. @$wfoo@ before @foo@), mirroring
    98 
    +     GHC's default dependency order (the wrapper calls the worker, so the worker
    99 
    +     comes first; specialisations likewise precede their origin). We rank by
    100 
    +     whether the OccName *contains* a '$', which marks a derived binder: a worker
    101 
    +     is @$wfoo@, but a call-site specialisation is tidied to @bar_$sfoo@ (no
    102 
    +     leading '$'), so a leading-'$' test would miss it.
    103 
    +  3. the OccName string, as a final lexical, deterministic tie-break.
    104 
    +
    105 
    +Recursive groups are never split: a 'Rec' is one 'CoreBind', placed as a unit by
    106 
    +its earliest-source member, with its members sorted by the same key.
    107 
    +
    108 
    +-dstable-core-dump-order is opt-in; the default order is retained because it is
    109 
    +useful for debugging the compiler itself.
    110 
    +-}
    111 
    +
    112 
    +-- | Reorder a 'CoreProgram' into a stable, source-location-driven order for
    113 
    +-- dumping. See Note [Stable Core dump order]. Used by 'dumpPassResult' when
    114 
    +-- -dstable-core-dump-order is enabled.
    115 
    +sortCoreBindingsForDump :: CoreProgram -> CoreProgram
    116 
    +sortCoreBindingsForDump = sortOn bindKey . map sortRecMembers
    117 
    +  where
    118 
    +    sortRecMembers (Rec prs) = Rec (sortOn (bndrKey . fst) prs)
    119 
    +    sortRecMembers b         = b
    120 
    +
    121 
    +    -- 'sortRecMembers' runs first, so a 'Rec' is already sorted by 'bndrKey'
    122 
    +    -- when 'bindKey' sees it; its first member is therefore the minimum key.
    123 
    +    bindKey :: CoreBind -> (Int, Int, Int, Int, String)
    124 
    +    bindKey (NonRec b _)     = bndrKey b
    125 
    +    bindKey (Rec ((b,_):_))  = bndrKey b
    126 
    +    bindKey (Rec [])         = panic "sortCoreBindingsForDump: empty Rec"
    127 
    +
    128 
    +    bndrKey :: CoreBndr -> (Int, Int, Int, Int, String)
    129 
    +    bndrKey b = (bucket, line, col, dollar_rank, s)
    130 
    +      where
    131 
    +        s = getOccString b
    132 
    +        (bucket, line, col) = case getSrcSpan b of
    133 
    +          RealSrcSpan rs _ -> (0, srcSpanStartLine rs, srcSpanStartCol rs)
    134 
    +          _                -> (1, 0, 0)  -- noSrcSpan: sort last
    135 
    +        -- A '$' anywhere in a tidied top-level OccName marks a compiler-derived
    136 
    +        -- binder ($wfoo, but also call-site specialisations tidied to
    137 
    +        -- bar_$sfoo); rank those before their origin within a shared source span,
    138 
    +        -- mirroring GHC's default dependency order (the wrapper calls the worker,
    139 
    +        -- so the worker comes first).
    140 
    +        dollar_rank | '$' `elem` s = 0
    141 
    +                    | otherwise    = 1
    142 
    +
    74 143 
     instance OutputableBndr b => Outputable (Bind b) where
    75 144 
         ppr bind = ppr_bind noAnn bind
    76 145

  • compiler/GHC/Driver/DynFlags.hs
    ... ... @@ -1594,6 +1594,7 @@ initSDocContext dflags style = SDC
    1594 1594 
       , sdocSuppressModulePrefixes      = gopt Opt_SuppressModulePrefixes dflags
    1595 1595 
       , sdocSuppressStgExts             = gopt Opt_SuppressStgExts dflags
    1596 1596 
       , sdocSuppressStgReps             = gopt Opt_SuppressStgReps dflags
    1597 
    +  , sdocStableCoreDumpOrder         = gopt Opt_StableCoreDumpOrder dflags
    1597 1598 
       , sdocErrorSpans                  = gopt Opt_ErrorSpans dflags
    1598 1599 
       , sdocStarIsType                  = xopt LangExt.StarIsType dflags
    1599 1600 
       , sdocLinearTypes                 = xopt LangExt.LinearTypes dflags

  • compiler/GHC/Driver/Flags.hs
    ... ... @@ -859,6 +859,10 @@ data GeneralFlag
    859 859 
        | Opt_SuppressTimestamps -- ^ Suppress timestamps in dumps
    860 860 
        | Opt_SuppressCoreSizes  -- ^ Suppress per binding Core size stats in dumps
    861 861
    862 
    +   -- | Reorder top-level bindings in Core dumps into a stable, diffable order.
    863 
    +   -- See Note [Stable Core dump order] in GHC.Core.Ppr.
    864 
    +   | Opt_StableCoreDumpOrder
    865 
    +
    862 866 
        -- Error message suppression
    863 867 
        | Opt_ShowErrorContext
    864 868

  • compiler/GHC/Driver/Session.hs
    ... ... @@ -2468,6 +2468,7 @@ dFlagsDeps = [
    2468 2468 
       flagSpec "ppr-case-as-let"            Opt_PprCaseAsLet,
    2469 2469 
       depFlagSpec' "ppr-ticks"              Opt_PprShowTicks
    2470 2470 
          (\turn_on -> useInstead "-d" "suppress-ticks" (not turn_on)),
    2471 
    +  flagSpec "stable-core-dump-order"     Opt_StableCoreDumpOrder,
    2471 2472 
       flagSpec "suppress-ticks"             Opt_SuppressTicks,
    2472 2473 
       depFlagSpec' "suppress-stg-free-vars" Opt_SuppressStgExts
    2473 2474 
          (useInstead "-d" "suppress-stg-exts"),

  • compiler/GHC/Utils/Outputable.hs
    ... ... @@ -422,6 +422,7 @@ data SDocContext = SDC
    422 422 
       , sdocSuppressModulePrefixes      :: !Bool
    423 423 
       , sdocSuppressStgExts             :: !Bool
    424 424 
       , sdocSuppressStgReps             :: !Bool
    425 
    +  , sdocStableCoreDumpOrder         :: !Bool
    425 426 
       , sdocErrorSpans                  :: !Bool
    426 427 
       , sdocStarIsType                  :: !Bool
    427 428 
       , sdocLinearTypes                 :: !Bool
    ... ... @@ -490,6 +491,7 @@ defaultSDocContext = SDC
    490 491 
       , sdocSuppressModulePrefixes      = False
    491 492 
       , sdocSuppressStgExts             = False
    492 493 
       , sdocSuppressStgReps             = True
    494 
    +  , sdocStableCoreDumpOrder         = False
    493 495 
       , sdocErrorSpans                  = False
    494 496 
       , sdocStarIsType                  = False
    495 497 
       , sdocLinearTypes                 = False

  • docs/users_guide/debugging.rst
    ... ... @@ -959,6 +959,33 @@ parts that you are not interested in.
    959 959 
         has shown you where to look, you can try again without
    960 960 
         :ghc-flag:`-dsuppress-uniques`
    961 961
    962 
    +.. ghc-flag:: -dstable-core-dump-order
    963 
    +    :shortdesc: Reorder top-level bindings in Core dumps into a stable,
    964 
    +        diffable order
    965 
    +    :type: dynamic
    966 
    +    :reverse: -dno-stable-core-dump-order
    967 
    +    :category: verbosity
    968 
    +
    969 
    +    :since: FIXME
    970 
    +
    971 
    +    Normally the order of top-level bindings in a Core dump (such as the
    972 
    +    output of :ghc-flag:`-ddump-simpl`) reflects the compiler's internal
    973 
    +    processing order, which depends on ``Unique`` values. Those uniques can
    974 
    +    shift whenever an unrelated upstream module changes, so the bindings get
    975 
    +    re-ordered and a textual ``diff`` of two dumps fails to line up the real
    976 
    +    changes.
    977 
    +
    978 
    +    This flag is opt-in and reorders the top-level bindings of Core dumps that
    979 
    +    go through the pass-result printer (e.g. :ghc-flag:`-ddump-simpl`,
    980 
    +    :ghc-flag:`-ddump-prep`, :ghc-flag:`-ddump-ds`,
    981 
    +    :ghc-flag:`-ddump-simpl-iterations`) into a stable, source-location-driven
    982 
    +    order that does not depend on uniques.
    983 
    +
    984 
    +    It is intended to be combined with :ghc-flag:`-dsuppress-uniques` when
    985 
    +    diffing two dumps, but because the ordering does not depend on uniques the
    986 
    +    output is also more diffable without it. The default (in-compiler) order is
    987 
    +    retained because it is useful when debugging the compiler itself.
    988 
    +
    962 989 
     .. ghc-flag:: -dsuppress-idinfo
    963 990 
         :shortdesc: Suppress extended information about identifiers where they
    964 991 
             are bound

  • testsuite/tests/simplCore/should_compile/Makefile
    ... ... @@ -298,3 +298,15 @@ T17901:
    298 298 
     	$(RM) -f T17901.o T17901.hi
    299 299 
     	'$(TEST_HC)' $(TEST_HC_OPTS) -O -c -ddump-simpl -dsuppress-uniques T17901.hs | grep 'wombat'
    300 300 
             # All three functions should get their case alternatives combined
    301 
    +
    302 
    +# T27296: check -dstable-core-dump-order on a small Data.Map-style module. The
    303 
    +# sed allow-list prints, deduplicated, the top-level binders we care about in
    304 
    +# dump order. It inspects names only, so it is insensitive to unrelated
    305 
    +# Core-format churn.
    306 
    +T27296:
    307 
    +	$(RM) -f T27296.o T27296.hi
    308 
    +	'$(TEST_HC)' $(TEST_HC_OPTS) -O -c -ddump-simpl -dsuppress-uniques \
    309 
    +	    -dsuppress-idinfo -dsuppress-module-prefixes -dno-typeable-binds \
    310 
    +	    -dstable-core-dump-order T27296.hs 2> /dev/null \
    311 
    +	    | sed -nE 's/^(\$$fEqKey|\$$fOrdKey|\$$fOrdKey_\$$ccompare|size|lookupG|member|findI|insertG|insertManyI|insertTwoI|weight|balance|ratios|fromAscI|\$$wweight|findI_\$$slookupG|fromAscI_\$$sinsertG|lvl)( .*)?$$/\1/p' \
    312 
    +	    | uniq

  • testsuite/tests/simplCore/should_compile/T27296.hs
    1 
    +{-# LANGUAGE BangPatterns #-}
    2 
    +
    3 
    +-- See #27296 and Note [Stable Core dump order] in GHC.Core.Ppr.
    4 
    +--
    5 
    +-- A small Data.Map-style module exercising the trickier parts of the stable
    6 
    +-- dump ordering: under -O it produces specialisations ($slookupG, $sinsertG),
    7 
    +-- a worker ($wweight), a floated lvl, and derived Eq/Ord instances for a custom
    8 
    +-- Key type, alongside the user functions. The source order is deliberately
    9 
    +-- neither alphabetical nor the default dump order (insertG forward-references
    10 
    +-- balance), so the test pins source-position ordering specifically.
    11 
    +module T27296
    12 
    +  ( Key(..), size, lookupG, member, findI, insertG, insertManyI, insertTwoI
    13 
    +  , weight, balance, ratios, fromAscI )
    14 
    +  where
    15 
    +
    16 
    +-- A custom key with a derived Ord instance: the derived $fEqKey/$fOrdKey
    17 
    +-- binders inherit this declaration's source span, so they cluster here.
    18 
    +data Key = Key Int deriving (Eq, Ord)
    19 
    +
    20 
    +data Map k a = Tip | Bin !Int k a !(Map k a) !(Map k a)
    21 
    +
    22 
    +data Sizes = Sizes !Int !Int
    23 
    +
    24 
    +size :: Map k a -> Int
    25 
    +size Tip              = 0
    26 
    +size (Bin sz _ _ _ _) = sz
    27 
    +
    28 
    +lookupG :: Ord k => k -> Map k a -> Maybe a
    29 
    +lookupG _ Tip = Nothing
    30 
    +lookupG k (Bin _ kx x l r) = case compare k kx of
    31 
    +  LT -> lookupG k l
    32 
    +  GT -> lookupG k r
    33 
    +  EQ -> Just x
    34 
    +{-# SPECIALISE lookupG :: Key -> Map Key a -> Maybe a #-}
    35 
    +
    36 
    +member :: Key -> Map Key a -> Bool
    37 
    +member k m = case lookupG k m of
    38 
    +  Nothing -> False
    39 
    +  Just _  -> True
    40 
    +
    41 
    +findI :: Key -> Map Key a -> a -> a
    42 
    +findI k m def = case lookupG k m of
    43 
    +  Nothing -> def
    44 
    +  Just v  -> v
    45 
    +
    46 
    +-- insertG references 'balance', which is defined further down (forward ref).
    47 
    +insertG :: Ord k => k -> a -> Map k a -> Map k a
    48 
    +insertG k x Tip = Bin 1 k x Tip Tip
    49 
    +insertG k x (Bin sz kx kv l r) = case compare k kx of
    50 
    +  LT -> balance kx kv (insertG k x l) r
    51 
    +  GT -> balance kx kv l (insertG k x r)
    52 
    +  EQ -> Bin sz k x l r
    53 
    +{-# SPECIALISE insertG :: Key -> a -> Map Key a -> Map Key a #-}
    54 
    +
    55 
    +insertManyI :: [(Key, a)] -> Map Key a -> Map Key a
    56 
    +insertManyI xs m0 = foldr (\(k, x) m -> insertG k x m) m0 xs
    57 
    +
    58 
    +insertTwoI :: Key -> Key -> a -> Map Key a
    59 
    +insertTwoI k1 k2 x = insertG k1 x (insertG k2 x Tip)
    60 
    +
    61 
    +-- weight unboxes the strict fields of Sizes -> worker/wrapper $wweight.
    62 
    +weight :: Sizes -> Int
    63 
    +weight (Sizes a b) = a * a + 3 * b * b + a * b + 1
    64 
    +
    65 
    +balance :: k -> a -> Map k a -> Map k a -> Map k a
    66 
    +balance k x l r = Bin (weight (Sizes sl sr)) k x l r
    67 
    +  where
    68 
    +    sl = size l
    69 
    +    sr = size r
    70 
    +
    71 
    +-- baseRatios is a closed constant under a lambda -> floated to a top-level lvl.
    72 
    +ratios :: Int -> [Int]
    73 
    +ratios n = map (n +) baseRatios
    74 
    +  where baseRatios = [2, 3, 5, 7, 11, 13]
    75 
    +
    76 
    +fromAscI :: [(Key, a)] -> Map Key a
    77 
    +fromAscI = foldr (\(k, x) m -> insertG k x m) Tip

  • testsuite/tests/simplCore/should_compile/T27296.stdout
    1 
    +$fEqKey
    2 
    +$fOrdKey
    3 
    +$fOrdKey_$ccompare
    4 
    +size
    5 
    +findI_$slookupG
    6 
    +lookupG
    7 
    +member
    8 
    +findI
    9 
    +fromAscI_$sinsertG
    10 
    +insertG
    11 
    +insertManyI
    12 
    +insertTwoI
    13 
    +$wweight
    14 
    +weight
    15 
    +balance
    16 
    +ratios
    17 
    +fromAscI
    18 
    +lvl

  • testsuite/tests/simplCore/should_compile/all.T
    ... ... @@ -602,3 +602,4 @@ test('T25718b', normal, compile, ['-O -ddump-simpl -dsuppress-uniques -dsuppress
    602 602 
     test('T25718c', normal, compile, ['-O -ddump-simpl -dsuppress-uniques -dsuppress-all -dno-typeable-binds'])
    603 603 
     test('T19166', normal, compile, ['-O -ddump-simpl -dsuppress-uniques -dsuppress-all -dno-typeable-binds'])
    604 604 
     test('T27261', [extra_files(['T27261_aux.hs'])], multimod_compile, ['T27261', '-v0 -O'])
    605 
    +test('T27296', [], makefile_test, ['T27296'])

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