ghc-9.12.1: GHC/StgToCmm.hs
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE LambdaCase #-}
-----------------------------------------------------------------------------
--
-- Stg to C-- code generation
--
-- (c) The University of Glasgow 2004-2006
--
-----------------------------------------------------------------------------
module GHC.StgToCmm ( codeGen ) where
import GHC.Prelude as Prelude
import GHC.Cmm.UniqueRenamer
import GHC.StgToCmm.Prof (initCostCentres, ldvEnter)
import GHC.StgToCmm.Monad
import GHC.StgToCmm.Env
import GHC.StgToCmm.Bind
import GHC.StgToCmm.DataCon
import GHC.StgToCmm.Layout
import GHC.StgToCmm.Utils
import GHC.StgToCmm.Closure
import GHC.StgToCmm.Config
import GHC.StgToCmm.Ticky
import GHC.StgToCmm.Types (ModuleLFInfos)
import GHC.StgToCmm.CgUtils (CgStream)
import GHC.Cmm
import GHC.Cmm.Utils
import GHC.Cmm.CLabel
import GHC.Cmm.Graph
import GHC.Stg.Syntax
import GHC.Types.CostCentre
import GHC.Types.IPE
import GHC.Types.Id
import GHC.Types.Id.Info
import GHC.Types.RepType
import GHC.Types.Basic
import GHC.Types.Var.Set ( isEmptyDVarSet )
import GHC.Types.Unique.DFM
import GHC.Types.Unique.FM
import GHC.Types.Name.Env
import GHC.Core.DataCon
import GHC.Core.TyCon
import GHC.Core.Multiplicity
import GHC.Utils.Error
import GHC.Utils.Outputable
import GHC.Utils.Logger
import GHC.Utils.TmpFs
import GHC.Data.Stream
import GHC.Data.OrdList
import Control.Monad (when,void, forM_)
import GHC.Utils.Misc
import System.IO.Unsafe
import qualified Data.ByteString as BS
import Data.IORef
import GHC.Utils.Panic
codeGen :: Logger
-> TmpFs
-> StgToCmmConfig
-> InfoTableProvMap
-> [TyCon]
-> CollectedCCs -- (Local/global) cost-centres needing declaring/registering.
-> [CgStgTopBinding] -- Bindings to convert
-> CgStream CmmGroup (ModuleLFInfos, DetUniqFM) -- See Note [Deterministic Uniques in the CG] on CgStream
-- Output as a stream, so codegen can
-- be interleaved with output
codeGen logger tmpfs cfg (InfoTableProvMap denv _ _) data_tycons
cost_centre_info stg_binds
= do { -- cg: run the code generator, and yield the resulting CmmGroup
-- Using an IORef to store the state is a bit crude, but otherwise
-- we would need to add a state monad layer which regresses
-- allocations by 0.5-2%.
; cgref <- liftIO $ initC >>= \s -> newIORef s
; uniqRnRef <- liftIO $ newIORef emptyDetUFM
; let fstate = initFCodeState $ stgToCmmPlatform cfg
; let cg :: FCode a -> CgStream CmmGroup a
cg fcode = do
(a, cmm) <- liftIO . withTimingSilent logger (text "STG -> Cmm") (`seq` ()) $ do
st <- readIORef cgref
rnm0 <- readIORef uniqRnRef
let
((a, cmm), st') = runC cfg fstate st (getCmm fcode)
(rnm1, cmm_renamed) =
-- Enable deterministic object code generation by
-- renaming uniques deterministically.
-- See Note [Object determinism]
if stgToCmmObjectDeterminism cfg
then detRenameCmmGroup rnm0 cmm -- The yielded cmm will already be renamed.
else (rnm0, removeDeterm cmm)
-- NB. stub-out cgs_tops and cgs_stmts. This fixes
-- a big space leak. DO NOT REMOVE!
-- This is observed by the #3294 test
writeIORef cgref $! (st'{ cgs_tops = nilOL, cgs_stmts = mkNop })
writeIORef uniqRnRef $! rnm1
return (a, cmm_renamed)
yield cmm
return a
; cg (mkModuleInit cost_centre_info)
; mapM_ (cg . cgTopBinding logger tmpfs cfg) stg_binds
-- Put datatype_stuff after code_stuff, because the
-- datatype closure table (for enumeration types) to
-- (say) PrelBase_True_closure, which is defined in
-- code_stuff
; let do_tycon tycon = do
-- Generate a table of static closures for an
-- enumeration type Note that the closure pointers are
-- tagged.
when (isEnumerationTyCon tycon) $ cg (cgEnumerationTyCon tycon)
-- Emit normal info_tables, for data constructors defined in this module.
mapM_ (cg . cgDataCon DefinitionSite) (tyConDataCons tycon)
; mapM_ do_tycon data_tycons
-- Emit special info tables for everything used in this module
-- This will only do something if `-fdistinct-info-tables` is turned on.
; mapM_ (\(dc, ns) -> forM_ ns $ \(k, _ss) -> cg (cgDataCon (UsageSite (stgToCmmThisModule cfg) k) dc)) (eltsUDFM denv)
; final_state <- liftIO (readIORef cgref)
; let cg_id_infos = cgs_binds final_state
-- See Note [Conveying CAF-info and LFInfo between modules] in
-- GHC.StgToCmm.Types
; let extractInfo info = (name, lf)
where
!name = idName (cg_id info)
!lf = cg_lf info
!generatedInfo
| stgToCmmOmitIfPragmas cfg
= emptyNameEnv
| otherwise
= mkNameEnv (Prelude.map extractInfo (nonDetEltsUFM cg_id_infos))
; rn_mapping <- liftIO (readIORef uniqRnRef)
; liftIO $ debugTraceMsg logger 3 (text "DetRnM mapping:" <+> ppr rn_mapping)
; return (generatedInfo, rn_mapping)
}
{-
Note [Object determinism]
~~~~~~~~~~~~~~~~~~~~~~~~~
Object determinism means that GHC, for the same exact input, produces,
deterministically, byte-for-byte identical objects (.o files, executables,
libraries...) on separate multi-threaded runs.
Deterministic objects are critical, for instance, for reproducible software
packaging and distribution, or build systems with content-sensitive
recompilation avoidance.
The main cause of non-determinism in objects comes from the non-deterministic
uniques leaking into the generated code. Apart from uniques previously affecting
determinism both directly by showing up in symbol labels and indirectly, e.g. in
the CLabel Ord instance, GHC already did a lot deterministically (modulo bugs)
by the time we set out to achieve full object determinism:
* The Simplifier is deterministic in the optimisations it applies (c.f. #25170)
* Interface files are deterministic (which depends on the previous bullet)
* The Cmm/NCG pipeline processes sections in a deterministic order, so the final
object sections, closures, data, etc., are already always outputted in the
same order for the same module.
Beyond fixing small bugs in the above bullets and other smaller non-determinism
leaks like the Ord instance of CLabels, we must ensure that/do the following to
make GHC produce fully deterministic objects:
* In STG -> Cmm, deterministically /rename/ all non-external uniques in the Cmm
chunk, deterministically, before yielding. See Note [Renaming uniques deterministically]
in GHC.Cmm.UniqueRenamer. This pass is necessary for object determinism but
is currently guarded by -fobject-determinism.
* Multiple Cmm passes work with non-deterministic @LabelMap@s -- that doesn't
change since they are both important for performance and do not affect the
determinism of the end result. As after the renaming pass the uniques are all
produced deterministically, the orderings observable by the map are also going
to be deterministic. In the brief period before a CmmGroup has been renamed,
a list instead of LabelMap is used to preserve the ordering.
See Note [DCmmGroup vs CmmGroup or: Deterministic Info Tables] in GHC.Cmm.
* In the code generation pipeline from Cmm onwards, when new uniques need to be
created for a given pass, use @UniqDSM@ instead of the previously used @UniqSM@.
@UniqDSM@ supplies uniques iteratively, guaranteeing uniques produced by the
backend are deterministic accross runs.
See Note [Deterministic Uniques in the CG] in GHC.Types.Unique.DSM.
Also, c.f. Note [Unique Determinism]
-}
---------------------------------------------------------------
-- Top-level bindings
---------------------------------------------------------------
{- 'cgTopBinding' is only used for top-level bindings, since they need
to be allocated statically (not in the heap) and need to be labelled.
No unboxed bindings can happen at top level.
In the code below, the static bindings are accumulated in the
@MkCgState@, and transferred into the ``statics'' slot by @forkStatics@.
This is so that we can write the top level processing in a compositional
style, with the increasing static environment being plumbed as a state
variable. -}
cgTopBinding :: Logger -> TmpFs -> StgToCmmConfig -> CgStgTopBinding -> FCode ()
cgTopBinding logger tmpfs cfg = \case
StgTopLifted (StgNonRec id rhs) -> do
let (info, fcode) = cgTopRhs cfg NonRecursive id rhs
fcode
addBindC info
StgTopLifted (StgRec pairs) -> do
let (bndrs, rhss) = unzip pairs
let pairs' = zip bndrs rhss
r = unzipWith (cgTopRhs cfg Recursive) pairs'
(infos, fcodes) = unzip r
addBindsC infos
sequence_ fcodes
StgTopStringLit id str -> do
let label = mkBytesLabel (idName id)
-- emit either a CmmString literal or dump the string in a file and emit a
-- CmmFileEmbed literal. If binary blobs aren't supported,
-- the threshold in `cfg` will be 0.
-- See Note [Embedding large binary blobs] in GHC.CmmToAsm.Ppr
let asString = case stgToCmmBinBlobThresh cfg of
Just bin_blob_threshold -> fromIntegral (BS.length str) <= bin_blob_threshold
Nothing -> True
(lit,decl) = if asString
then mkByteStringCLit label str
else unsafePerformIO $ do
bFile <- newTempName logger tmpfs (stgToCmmTmpDir cfg) TFL_CurrentModule ".dat"
BS.writeFile bFile str
return $ mkFileEmbedLit label bFile (BS.length str)
emitDecl decl
addBindC (litIdInfo (stgToCmmPlatform cfg) id mkLFStringLit lit)
cgTopRhs :: StgToCmmConfig -> RecFlag -> Id -> CgStgRhs -> (CgIdInfo, FCode ())
-- The Id is passed along for setting up a binding...
cgTopRhs cfg _rec bndr (StgRhsCon _cc con mn _ts args _typ)
= cgTopRhsCon cfg bndr con mn (assertNonVoidStgArgs args)
-- con args are always non-void,
-- see Note [Post-unarisation invariants] in GHC.Stg.Unarise
cgTopRhs cfg rec bndr (StgRhsClosure fvs cc upd_flag args body _typ)
= assertPpr (isEmptyDVarSet fvs) (text "fvs:" <> ppr fvs) $ -- There should be no free variables
cgTopRhsClosure (stgToCmmPlatform cfg) rec bndr cc upd_flag args body
---------------------------------------------------------------
-- Module initialisation code
---------------------------------------------------------------
mkModuleInit
:: CollectedCCs -- cost centre info
-> FCode ()
mkModuleInit cost_centre_info
= do { initCostCentres cost_centre_info
}
---------------------------------------------------------------
-- Generating static stuff for algebraic data types
---------------------------------------------------------------
cgEnumerationTyCon :: TyCon -> FCode ()
cgEnumerationTyCon tycon
= do platform <- getPlatform
emitRODataLits (mkClosureTableLabel (tyConName tycon) NoCafRefs)
[ CmmLabelOff (mkClosureLabel (dataConName con) NoCafRefs)
(tagForCon platform con)
| con <- tyConDataCons tycon]
cgDataCon :: ConInfoTableLocation -> DataCon -> FCode ()
-- Generate the entry code, info tables, and (for niladic constructor)
-- the static closure, for a constructor.
cgDataCon mn data_con
= do { massert (not (isUnboxedTupleDataCon data_con || isUnboxedSumDataCon data_con))
; profile <- getProfile
; platform <- getPlatform
; let
(tot_wds, -- #ptr_wds + #nonptr_wds
ptr_wds) -- #ptr_wds
= mkVirtConstrSizes profile arg_reps
nonptr_wds = tot_wds - ptr_wds
dyn_info_tbl =
mkDataConInfoTable profile data_con mn False ptr_wds nonptr_wds
-- We're generating info tables, so we don't know and care about
-- what the actual arguments are. Using () here as the place holder.
arg_reps :: [PrimRep]
arg_reps = [ rep_ty
| ty <- dataConRepArgTys data_con
, rep_ty <- typePrimRep (scaledThing ty)
]
; emitClosureAndInfoTable platform dyn_info_tbl NativeDirectCall [] $
-- NB: the closure pointer is assumed *untagged* on
-- entry to a constructor. If the pointer is tagged,
-- then we should not be entering it. This assumption
-- is used in ldvEnter and when tagging the pointer to
-- return it.
-- NB 2: We don't set CC when entering data (WDP 94/06)
do { tickyEnterDynCon
; let node = CmmReg $ nodeReg platform
; ldvEnter node
; tickyReturnOldCon (length arg_reps)
; void $ emitReturn [cmmOffsetB platform node (tagForCon platform data_con)]
}
-- The case continuation code expects a tagged pointer
}