path: root/compiler/GHC/StgToCmm/Prof.hs

-----------------------------------------------------------------------------
--
-- Code generation for profiling
--
-- (c) The University of Glasgow 2004-2006
--
-----------------------------------------------------------------------------

module GHC.StgToCmm.Prof (
        initCostCentres, ccType, ccsType,
        mkCCostCentre, mkCCostCentreStack,

        -- Cost-centre Profiling
        dynProfHdr, profDynAlloc, profAlloc, staticProfHdr, initUpdFrameProf,
        enterCostCentreThunk, enterCostCentreFun,
        costCentreFrom,
        storeCurCCS,
        emitSetCCC,

        saveCurrentCostCentre, restoreCurrentCostCentre,

        -- Lag/drag/void stuff
        ldvEnter, ldvEnterClosure, ldvRecordCreate
  ) where

import GHC.Prelude

import GHC.Platform
import GHC.StgToCmm.Closure
import GHC.StgToCmm.Utils
import GHC.StgToCmm.Monad
import GHC.Runtime.Heap.Layout

import GHC.Cmm.Graph
import GHC.Cmm
import GHC.Cmm.Utils
import GHC.Cmm.CLabel

import GHC.Types.CostCentre
import GHC.Driver.Session
import GHC.Data.FastString
import GHC.Unit.Module as Module
import GHC.Utils.Outputable

import Control.Monad
import Data.Char (ord)

-----------------------------------------------------------------------------
--
-- Cost-centre-stack Profiling
--
-----------------------------------------------------------------------------

-- Expression representing the current cost centre stack
ccsType :: Platform -> CmmType -- Type of a cost-centre stack
ccsType = bWord

ccType :: Platform -> CmmType -- Type of a cost centre
ccType = bWord

storeCurCCS :: CmmExpr -> CmmAGraph
storeCurCCS e = mkAssign cccsReg e

mkCCostCentre :: CostCentre -> CmmLit
mkCCostCentre cc = CmmLabel (mkCCLabel cc)

mkCCostCentreStack :: CostCentreStack -> CmmLit
mkCCostCentreStack ccs = CmmLabel (mkCCSLabel ccs)

costCentreFrom :: DynFlags
               -> CmmExpr         -- A closure pointer
               -> CmmExpr        -- The cost centre from that closure
costCentreFrom dflags cl = CmmLoad (cmmOffsetB platform cl (oFFSET_StgHeader_ccs dflags)) (ccsType platform)
  where platform = targetPlatform dflags

-- | The profiling header words in a static closure
staticProfHdr :: DynFlags -> CostCentreStack -> [CmmLit]
staticProfHdr dflags ccs
  | gopt Opt_SccProfilingOn dflags = [mkCCostCentreStack ccs, staticLdvInit platform]
  | otherwise                      = []
  where platform = targetPlatform dflags

-- | Profiling header words in a dynamic closure
dynProfHdr :: DynFlags -> CmmExpr -> [CmmExpr]
dynProfHdr dflags ccs
  | gopt Opt_SccProfilingOn dflags = [ccs, dynLdvInit dflags]
  | otherwise                      = []

-- | Initialise the profiling field of an update frame
initUpdFrameProf :: CmmExpr -> FCode ()
initUpdFrameProf frame
  = ifProfiling $        -- frame->header.prof.ccs = CCCS
    do dflags <- getDynFlags
       platform <- getPlatform
       emitStore (cmmOffset platform frame (oFFSET_StgHeader_ccs dflags)) cccsExpr
        -- frame->header.prof.hp.rs = NULL (or frame-header.prof.hp.ldvw = 0)
        -- is unnecessary because it is not used anyhow.

---------------------------------------------------------------------------
--         Saving and restoring the current cost centre
---------------------------------------------------------------------------

{-        Note [Saving the current cost centre]
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The current cost centre is like a global register.  Like other
global registers, it's a caller-saves one.  But consider
        case (f x) of (p,q) -> rhs
Since 'f' may set the cost centre, we must restore it
before resuming rhs.  So we want code like this:
        local_cc = CCC  -- save
        r = f( x )
        CCC = local_cc  -- restore
That is, we explicitly "save" the current cost centre in
a LocalReg, local_cc; and restore it after the call. The
C-- infrastructure will arrange to save local_cc across the
call.

The same goes for join points;
        let j x = join-stuff
        in blah-blah
We want this kind of code:
        local_cc = CCC  -- save
        blah-blah
     J:
        CCC = local_cc  -- restore
-}

saveCurrentCostCentre :: FCode (Maybe LocalReg)
        -- Returns Nothing if profiling is off
saveCurrentCostCentre
  = do dflags <- getDynFlags
       platform <- getPlatform
       if not (gopt Opt_SccProfilingOn dflags)
           then return Nothing
           else do local_cc <- newTemp (ccType platform)
                   emitAssign (CmmLocal local_cc) cccsExpr
                   return (Just local_cc)

restoreCurrentCostCentre :: Maybe LocalReg -> FCode ()
restoreCurrentCostCentre Nothing
  = return ()
restoreCurrentCostCentre (Just local_cc)
  = emit (storeCurCCS (CmmReg (CmmLocal local_cc)))


-------------------------------------------------------------------------------
-- Recording allocation in a cost centre
-------------------------------------------------------------------------------

-- | Record the allocation of a closure.  The CmmExpr is the cost
-- centre stack to which to attribute the allocation.
profDynAlloc :: SMRep -> CmmExpr -> FCode ()
profDynAlloc rep ccs
  = ifProfiling $
    do dflags <- getDynFlags
       platform <- getPlatform
       profAlloc (mkIntExpr platform (heapClosureSizeW dflags rep)) ccs

-- | Record the allocation of a closure (size is given by a CmmExpr)
-- The size must be in words, because the allocation counter in a CCS counts
-- in words.
profAlloc :: CmmExpr -> CmmExpr -> FCode ()
profAlloc words ccs
  = ifProfiling $
        do dflags <- getDynFlags
           platform <- getPlatform
           let alloc_rep = rEP_CostCentreStack_mem_alloc dflags
           emit (addToMemE alloc_rep
                       (cmmOffsetB platform ccs (oFFSET_CostCentreStack_mem_alloc dflags))
                       (CmmMachOp (MO_UU_Conv (wordWidth platform) (typeWidth alloc_rep)) $
                         [CmmMachOp (mo_wordSub platform) [words,
                                                           mkIntExpr platform (profHdrSize dflags)]]))
                       -- subtract the "profiling overhead", which is the
                       -- profiling header in a closure.

-- -----------------------------------------------------------------------
-- Setting the current cost centre on entry to a closure

enterCostCentreThunk :: CmmExpr -> FCode ()
enterCostCentreThunk closure =
  ifProfiling $ do
      dflags <- getDynFlags
      emit $ storeCurCCS (costCentreFrom dflags closure)

enterCostCentreFun :: CostCentreStack -> CmmExpr -> FCode ()
enterCostCentreFun ccs closure =
  ifProfiling $ do
    if isCurrentCCS ccs
       then do dflags <- getDynFlags
               emitRtsCall rtsUnitId (fsLit "enterFunCCS")
                   [(baseExpr, AddrHint),
                    (costCentreFrom dflags closure, AddrHint)] False
       else return () -- top-level function, nothing to do

ifProfiling :: FCode () -> FCode ()
ifProfiling code
  = do dflags <- getDynFlags
       if gopt Opt_SccProfilingOn dflags
           then code
           else return ()

---------------------------------------------------------------
--        Initialising Cost Centres & CCSs
---------------------------------------------------------------

initCostCentres :: CollectedCCs -> FCode ()
-- Emit the declarations
initCostCentres (local_CCs, singleton_CCSs)
  = do dflags <- getDynFlags
       when (gopt Opt_SccProfilingOn dflags) $
           do mapM_ emitCostCentreDecl local_CCs
              mapM_ emitCostCentreStackDecl singleton_CCSs


emitCostCentreDecl :: CostCentre -> FCode ()
emitCostCentreDecl cc = do
  { dflags <- getDynFlags
  ; platform <- getPlatform
  ; let is_caf | isCafCC cc = mkIntCLit platform (ord 'c') -- 'c' == is a CAF
               | otherwise  = zero platform
                        -- NB. bytesFS: we want the UTF-8 bytes here (#5559)
  ; label <- newByteStringCLit (bytesFS $ costCentreUserNameFS cc)
  ; modl  <- newByteStringCLit (bytesFS $ moduleNameFS
                                        $ moduleName
                                        $ cc_mod cc)
  ; loc <- newByteStringCLit $ bytesFS $ mkFastString $
                   showPpr dflags (costCentreSrcSpan cc)
           -- XXX going via FastString to get UTF-8 encoding is silly
  ; let
     lits = [ zero platform,  -- StgInt ccID,
              label,          -- char *label,
              modl,           -- char *module,
              loc,            -- char *srcloc,
              zero64,         -- StgWord64 mem_alloc
              zero platform,  -- StgWord time_ticks
              is_caf,         -- StgInt is_caf
              zero platform   -- struct _CostCentre *link
            ]
  ; emitDataLits (mkCCLabel cc) lits
  }

emitCostCentreStackDecl :: CostCentreStack -> FCode ()
emitCostCentreStackDecl ccs
  = case maybeSingletonCCS ccs of
    Just cc ->
        do dflags <- getDynFlags
           platform <- getPlatform
           let mk_lits cc = zero platform :
                            mkCCostCentre cc :
                            replicate (sizeof_ccs_words dflags - 2) (zero platform)
                -- Note: to avoid making any assumptions about how the
                -- C compiler (that compiles the RTS, in particular) does
                -- layouts of structs containing long-longs, simply
                -- pad out the struct with zero words until we hit the
                -- size of the overall struct (which we get via DerivedConstants.h)
           emitDataLits (mkCCSLabel ccs) (mk_lits cc)
    Nothing -> pprPanic "emitCostCentreStackDecl" (ppr ccs)

zero :: Platform -> CmmLit
zero platform = mkIntCLit platform 0
zero64 :: CmmLit
zero64 = CmmInt 0 W64

sizeof_ccs_words :: DynFlags -> Int
sizeof_ccs_words dflags
    -- round up to the next word.
  | ms == 0   = ws
  | otherwise = ws + 1
  where
   platform = targetPlatform dflags
   (ws,ms) = sIZEOF_CostCentreStack dflags `divMod` platformWordSizeInBytes platform

-- ---------------------------------------------------------------------------
-- Set the current cost centre stack

emitSetCCC :: CostCentre -> Bool -> Bool -> FCode ()
emitSetCCC cc tick push
 = do dflags <- getDynFlags
      platform <- getPlatform
      if not (gopt Opt_SccProfilingOn dflags)
          then return ()
          else do tmp <- newTemp (ccsType platform)
                  pushCostCentre tmp cccsExpr cc
                  when tick $ emit (bumpSccCount dflags (CmmReg (CmmLocal tmp)))
                  when push $ emit (storeCurCCS (CmmReg (CmmLocal tmp)))

pushCostCentre :: LocalReg -> CmmExpr -> CostCentre -> FCode ()
pushCostCentre result ccs cc
  = emitRtsCallWithResult result AddrHint
        rtsUnitId
        (fsLit "pushCostCentre") [(ccs,AddrHint),
                                (CmmLit (mkCCostCentre cc), AddrHint)]
        False

bumpSccCount :: DynFlags -> CmmExpr -> CmmAGraph
bumpSccCount dflags ccs
  = addToMem (rEP_CostCentreStack_scc_count dflags)
         (cmmOffsetB platform ccs (oFFSET_CostCentreStack_scc_count dflags)) 1
  where platform = targetPlatform dflags

-----------------------------------------------------------------------------
--
--                Lag/drag/void stuff
--
-----------------------------------------------------------------------------

--
-- Initial value for the LDV field in a static closure
--
staticLdvInit :: Platform -> CmmLit
staticLdvInit = zeroCLit

--
-- Initial value of the LDV field in a dynamic closure
--
dynLdvInit :: DynFlags -> CmmExpr
dynLdvInit dflags =     -- (era << LDV_SHIFT) | LDV_STATE_CREATE
  CmmMachOp (mo_wordOr platform) [
      CmmMachOp (mo_wordShl platform) [loadEra dflags, mkIntExpr platform (lDV_SHIFT dflags)],
      CmmLit (mkWordCLit platform (iLDV_STATE_CREATE dflags))
  ]
  where
   platform = targetPlatform dflags

--
-- Initialise the LDV word of a new closure
--
ldvRecordCreate :: CmmExpr -> FCode ()
ldvRecordCreate closure = do
  dflags <- getDynFlags
  emit $ mkStore (ldvWord dflags closure) (dynLdvInit dflags)

--
-- | Called when a closure is entered, marks the closure as having
-- been "used".  The closure is not an "inherently used" one.  The
-- closure is not @IND@ because that is not considered for LDV profiling.
--
ldvEnterClosure :: ClosureInfo -> CmmReg -> FCode ()
ldvEnterClosure closure_info node_reg = do
    dflags <- getDynFlags
    platform <- getPlatform
    let tag = funTag dflags closure_info
    -- don't forget to subtract node's tag
    ldvEnter (cmmOffsetB platform (CmmReg node_reg) (-tag))

ldvEnter :: CmmExpr -> FCode ()
-- Argument is a closure pointer
ldvEnter cl_ptr = do
    dflags <- getDynFlags
    platform <- getPlatform
    let -- don't forget to subtract node's tag
        ldv_wd = ldvWord dflags cl_ptr
        new_ldv_wd = cmmOrWord platform
                        (cmmAndWord platform (CmmLoad ldv_wd (bWord platform))
                                             (CmmLit (mkWordCLit platform (iLDV_CREATE_MASK dflags))))
                        (cmmOrWord platform (loadEra dflags) (CmmLit (mkWordCLit platform (iLDV_STATE_USE dflags))))
    ifProfiling $
         -- if (era > 0) {
         --    LDVW((c)) = (LDVW((c)) & LDV_CREATE_MASK) |
         --                era | LDV_STATE_USE }
        emit =<< mkCmmIfThenElse (CmmMachOp (mo_wordUGt platform) [loadEra dflags, CmmLit (zeroCLit platform)])
                     (mkStore ldv_wd new_ldv_wd)
                     mkNop

loadEra :: DynFlags -> CmmExpr
loadEra dflags = CmmMachOp (MO_UU_Conv (cIntWidth dflags) (wordWidth platform))
    [CmmLoad (mkLblExpr (mkRtsCmmDataLabel (fsLit "era")))
             (cInt dflags)]
    where platform = targetPlatform dflags

ldvWord :: DynFlags -> CmmExpr -> CmmExpr
-- Takes the address of a closure, and returns
-- the address of the LDV word in the closure
ldvWord dflags closure_ptr
    = cmmOffsetB platform closure_ptr (oFFSET_StgHeader_ldvw dflags)
    where platform = targetPlatform dflags