CmmPipeline.hs 9.5 KB
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{-# OPTIONS_GHC -XNoMonoLocalBinds #-}
-- Norman likes local bindings
-- If this module lives on I'd like to get rid of this flag in due course
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module CmmPipeline (
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  -- | Converts C-- with an implicit stack and native C-- calls into
  -- optimized, CPS converted and native-call-less C--.  The latter
  -- C-- can be used to generate assembly.
  cmmPipeline
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) where
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import CLabel
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import Cmm
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import CmmLint
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import CmmLive
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import CmmBuildInfoTables
import CmmCommonBlockElim
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import CmmProcPoint
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import CmmSpillReload
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import CmmRewriteAssignments
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import CmmStackLayout
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import CmmContFlowOpt
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import OptimizationFuel
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import DynFlags
import ErrUtils
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import HscTypes
import Data.Maybe
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import Control.Monad
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import Data.Map (Map)
import qualified Data.Map as Map
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import Data.Set (Set)
import qualified Data.Set as Set
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import Outputable
import StaticFlags
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-----------------------------------------------------------------------------
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-- | Top level driver for C-- pipeline
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-----------------------------------------------------------------------------
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-- There are two complications here:
-- 1. We need to compile the procedures in two stages because we need
--    an analysis of the procedures to tell us what CAFs they use.
--    The first stage returns a map from procedure labels to CAFs,
--    along with a closure that will compute SRTs and attach them to
--    the compiled procedures.
--    The second stage is to combine the CAF information into a top-level
--    CAF environment mapping non-static closures to the CAFs they keep live,
--    then pass that environment to the closures returned in the first
--    stage of compilation.
-- 2. We need to thread the module's SRT around when the SRT tables
--    are computed for each procedure.
--    The SRT needs to be threaded because it is grown lazily.
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-- 3. We run control flow optimizations twice, once before any pipeline
--    work is done, and once again at the very end on all of the
--    resulting C-- blocks.  EZY: It's unclear whether or not whether
--    we actually need to do the initial pass.
cmmPipeline  :: HscEnv -- Compilation env including
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                       -- dynamic flags: -dcmm-lint -ddump-cps-cmm
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             -> TopSRT     -- SRT table and accumulating list of compiled procs
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             -> CmmGroup             -- Input C-- with Procedures
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             -> IO (TopSRT, CmmGroup) -- Output CPS transformed C--
cmmPipeline hsc_env topSRT prog =
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  do let dflags = hsc_dflags hsc_env
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     --
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     showPass dflags "CPSZ"
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     (cafEnvs, tops) <- liftM unzip $ mapM (cpsTop hsc_env) prog
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     -- tops :: [[(CmmDecl,CAFSet]]  (one list per group)
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     let topCAFEnv = mkTopCAFInfo (concat cafEnvs)
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     -- folding over the groups
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     (topSRT, tops) <- foldM (toTops hsc_env topCAFEnv) (topSRT, []) tops
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     let cmms :: CmmGroup
         cmms = reverse (concat tops)
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     dumpIfSet_dyn dflags Opt_D_dump_cps_cmm "Post CPS Cmm" (pprPlatform (targetPlatform dflags) cmms)
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     return (topSRT, cmms)
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{- [Note global fuel]
~~~~~~~~~~~~~~~~~~~~~
The identity and the last pass are stored in
mutable reference cells in an 'HscEnv' and are
global to one compiler session.
-}

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-- EZY: It might be helpful to have an easy way of dumping the "pre"
-- input for any given phase, besides just turning it all on with
-- -ddump-cmmz

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cpsTop :: HscEnv -> CmmDecl -> IO ([(CLabel, CAFSet)], [(CAFSet, CmmDecl)])
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cpsTop _ p@(CmmData {}) = return ([], [(Set.empty, p)])
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cpsTop hsc_env (CmmProc h@(TopInfo {stack_info=StackInfo {arg_space=entry_off}}) l g) =
    do
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       -- Why bother doing these early: dualLivenessWithInsertion,
       -- insertLateReloads, rewriteAssignments?
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       ----------- Control-flow optimisations ---------------
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       g <- {-# SCC "cmmCfgOpts(1)" #-} return $ cmmCfgOpts g
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       dump Opt_D_dump_cmmz_cfg "Post control-flow optimsations" g

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       ----------- Eliminate common blocks -------------------
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       g <- {-# SCC "elimCommonBlocks" #-} return $ elimCommonBlocks g
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       dump Opt_D_dump_cmmz_cbe "Post common block elimination" g
       -- Any work storing block Labels must be performed _after_
       -- elimCommonBlocks
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       ----------- Proc points -------------------
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       let callPPs = {-# SCC "callProcPoints" #-} callProcPoints g
       procPoints <- {-# SCC "minimalProcPointSet" #-} run $ minimalProcPointSet (targetPlatform dflags) callPPs g
       g <- {-# SCC "addProcPointProtocols" #-} run $ addProcPointProtocols callPPs procPoints g
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       dump Opt_D_dump_cmmz_proc "Post Proc Points Added" g
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       ----------- Spills and reloads -------------------
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       g <- {-# SCC "dualLivenessWithInsertion" #-} run $ dualLivenessWithInsertion procPoints g
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       dump Opt_D_dump_cmmz_spills "Post spills and reloads" g
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       ----------- Sink and inline assignments -------------------
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       g <- {-# SCC "rewriteAssignments" #-} runOptimization $ rewriteAssignments platform g
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       dump Opt_D_dump_cmmz_rewrite "Post rewrite assignments" g
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       ----------- Eliminate dead assignments -------------------
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       g <- {-# SCC "removeDeadAssignments" #-} runOptimization $ removeDeadAssignments g
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       dump Opt_D_dump_cmmz_dead "Post remove dead assignments" g
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       ----------- Zero dead stack slots (Debug only) ---------------
       -- Debugging: stubbing slots on death can cause crashes early
       g <- if opt_StubDeadValues
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                then {-# SCC "stubSlotsOnDeath" #-} run $ stubSlotsOnDeath g
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                else return g
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       dump Opt_D_dump_cmmz_stub "Post stub dead stack slots" g
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       --------------- Stack layout ----------------
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       slotEnv <- {-# SCC "liveSlotAnal" #-} run $ liveSlotAnal g
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       let spEntryMap = getSpEntryMap entry_off g
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       mbpprTrace "live slot analysis results: " (ppr slotEnv) $ return ()
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       let areaMap = {-# SCC "layout" #-} layout procPoints spEntryMap slotEnv entry_off g
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       mbpprTrace "areaMap" (ppr areaMap) $ return ()

       ------------  Manifest the stack pointer --------
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       g  <- {-# SCC "manifestSP" #-} run $ manifestSP spEntryMap areaMap entry_off g
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       dump Opt_D_dump_cmmz_sp "Post manifestSP" g
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       -- UGH... manifestSP can require updates to the procPointMap.
       -- We can probably do something quicker here for the update...

       ------------- Split into separate procedures ------------
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       procPointMap  <- {-# SCC "procPointAnalysis" #-} run $ procPointAnalysis procPoints g
       dumpWith dflags ppr Opt_D_dump_cmmz_procmap "procpoint map" procPointMap
       gs <- {-# SCC "splitAtProcPoints" #-} run $ splitAtProcPoints l callPPs procPoints procPointMap
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                                       (CmmProc h l g)
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       dumps Opt_D_dump_cmmz_split "Post splitting" gs
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       ------------- More CAFs and foreign calls ------------
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       cafEnv <- {-# SCC "cafAnal" #-} run $ cafAnal platform g
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       let localCAFs = catMaybes $ map (localCAFInfo platform cafEnv) gs
       mbpprTrace "localCAFs" (pprPlatform platform localCAFs) $ return ()
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       gs <- {-# SCC "lowerSafeForeignCalls" #-} run $ mapM (lowerSafeForeignCalls areaMap) gs
       dumps Opt_D_dump_cmmz_lower "Post lowerSafeForeignCalls" gs
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       -- NO MORE GRAPH TRANSFORMATION AFTER HERE -- JUST MAKING INFOTABLES
       gs <- {-# SCC "setInfoTableStackMap" #-} return $ map (setInfoTableStackMap slotEnv areaMap) gs
       dumps Opt_D_dump_cmmz_info "after setInfoTableStackMap" gs

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       ----------- Control-flow optimisations ---------------
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       gs <- {-# SCC "cmmCfgOpts(2)" #-} return $ map cmmCfgOptsProc gs
       dumps Opt_D_dump_cmmz_cfg "Post control-flow optimsations" gs
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       gs <- {-# SCC "bundleCAFs" #-} return $ map (bundleCAFs cafEnv) gs
       dumps Opt_D_dump_cmmz_cafs "after bundleCAFs" gs
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       return (localCAFs, gs)
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              -- gs        :: [ (CAFSet, CmmDecl) ]
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              -- localCAFs :: [ (CLabel, CAFSet) ] -- statics filtered out(?)

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  where dflags = hsc_dflags hsc_env
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        platform = targetPlatform dflags
        mbpprTrace x y z | dopt Opt_D_dump_cmmz dflags = pprTrace x y z
                         | otherwise = z
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        dump = dumpGraph dflags

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        dumps flag name
           = mapM_ (dumpWith dflags (pprPlatform platform) flag name)

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        -- Runs a required transformation/analysis
        run = runInfiniteFuelIO (hsc_OptFuel hsc_env)
        -- Runs an optional transformation/analysis (and should
        -- thus be subject to optimization fuel)
        runOptimization = runFuelIO (hsc_OptFuel hsc_env)

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dumpGraph :: DynFlags -> DynFlag -> String -> CmmGraph -> IO ()
dumpGraph dflags flag name g = do
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  cmmLint g
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  dumpWith dflags (pprPlatform (targetPlatform dflags)) flag name g

dumpWith :: DynFlags -> (a -> SDoc) -> DynFlag -> String -> a -> IO ()
dumpWith dflags pprFun flag txt g = do
         -- ToDo: No easy way of say "dump all the cmmz, *and* split
         -- them into files."  Also, -ddump-cmmz doesn't play nicely
         -- with -ddump-to-file, since the headers get omitted.
   dumpIfSet_dyn dflags flag txt (pprFun g)
   when (not (dopt flag dflags)) $
      dumpIfSet_dyn dflags Opt_D_dump_cmmz txt (pprFun g)
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-- This probably belongs in CmmBuildInfoTables?
-- We're just finishing the job here: once we know what CAFs are defined
-- in non-static closures, we can build the SRTs.
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toTops :: HscEnv -> Map CLabel CAFSet -> (TopSRT, [[CmmDecl]])
                 -> [(CAFSet, CmmDecl)] -> IO (TopSRT, [[CmmDecl]])
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toTops hsc_env topCAFEnv (topSRT, tops) gs =
  do let setSRT (topSRT, rst) g =
           do (topSRT, gs) <- setInfoTableSRT topCAFEnv topSRT g
              return (topSRT, gs : rst)
     (topSRT, gs') <- runFuelIO (hsc_OptFuel hsc_env) $ foldM setSRT (topSRT, []) gs
     return (topSRT, concat gs' : tops)