-module CmmCPS (cmmCPS) where
+module CmmCPS (
+ -- | Converts C-- with full proceedures and parameters
+ -- to a CPS transformed C-- with the stack made manifest.
+ cmmCPS
+) where
#include "HsVersions.h"
import CmmLint
import PprCmm
-import Dataflow (mapCmmTop, onBasicBlock, cmmLivenessComment, cmmLiveness)
+import Dataflow
+import CmmLive
+import CmmBrokenBlock
+import CmmProcPoint
+import CmmCallConv
+
+import MachOp
+import ForeignCall
+import CLabel
+import SMRep
+import Constants
import DynFlags
import ErrUtils
import Maybes
import Outputable
+import UniqSupply
+import UniqFM
+import UniqSet
+import Unique
import Monad
import IO
+import Data.List
-cmmCPS :: DynFlags
- -> [Cmm] -- C-- with Proceedures
- -> IO [Cmm] -- Output: CPS transformed C--
-
+-----------------------------------------------------------------------------
+-- |Top level driver for the CPS pass
+-----------------------------------------------------------------------------
+cmmCPS :: DynFlags -- ^ Dynamic flags: -dcmm-lint -ddump-cps-cmm
+ -> [Cmm] -- ^ Input C-- with Proceedures
+ -> IO [Cmm] -- ^ Output CPS transformed C--
cmmCPS dflags abstractC = do
when (dopt Opt_DoCmmLinting dflags) $
do showPass dflags "CmmLint"
ghcExit dflags 1
Nothing -> return ()
showPass dflags "CPS"
- -- continuationC <- return abstractC
- continuationC <- return $ map (mapCmmTop (onBasicBlock (\bs -> map (cmmLivenessComment (cmmLiveness bs)) bs))) abstractC
+
+ -- TODO: more lint checking
+ -- check for use of branches to non-existant blocks
+ -- check for use of Sp, SpLim, R1, R2, etc.
+
+ uniqSupply <- mkSplitUniqSupply 'p'
+ let supplies = listSplitUniqSupply uniqSupply
+ let doCpsProc s (Cmm c) =
+ Cmm $ concat $ zipWith cpsProc (listSplitUniqSupply s) c
+ let continuationC = zipWith doCpsProc supplies abstractC
dumpIfSet_dyn dflags Opt_D_dump_cps_cmm "CPS Cmm" (pprCmms continuationC)
+
-- TODO: add option to dump Cmm to file
+
return continuationC
+
+-----------------------------------------------------------------------------
+-- |CPS a single CmmTop (proceedure)
+-- Only 'CmmProc' are transformed 'CmmData' will be left alone.
+-----------------------------------------------------------------------------
+
+cpsProc :: UniqSupply
+ -> CmmTop -- ^Input proceedure
+ -> [CmmTop] -- ^Output proceedure and continuations
+cpsProc uniqSupply x@(CmmData _ _) = [x]
+cpsProc uniqSupply x@(CmmProc info_table ident params blocks) = cps_procs
+ where
+ uniqes :: [[Unique]]
+ uniqes = map uniqsFromSupply $ listSplitUniqSupply uniqSupply
+
+ -- Break the block at each function call.
+ -- The part after the function call will have to become a continuation.
+ broken_blocks :: [BrokenBlock]
+ broken_blocks =
+ concat $ zipWith3 breakBlock uniqes blocks
+ (FunctionEntry ident params:repeat ControlEntry)
+
+ -- Calculate live variables for each broken block.
+ --
+ -- Nothing can be live on entry to the first block
+ -- so we could take the tail, but for now we wont
+ -- to help future proof the code.
+ live :: BlockEntryLiveness
+ live = cmmLiveness $ map cmmBlockFromBrokenBlock broken_blocks
+
+ -- Calculate which blocks must be made into full fledged procedures.
+ proc_points :: UniqSet BlockId
+ proc_points = calculateProcPoints broken_blocks
+
+ -- Construct a map so we can lookup a broken block by its 'BlockId'.
+ block_env :: BlockEnv BrokenBlock
+ block_env = blocksToBlockEnv broken_blocks
+
+ -- Group the blocks into continuations based on the set of proc-points.
+ continuations :: [Continuation]
+ continuations = map (gatherBlocksIntoContinuation proc_points block_env)
+ (uniqSetToList proc_points)
+
+ -- Select the stack format on entry to each continuation.
+ --
+ -- This is an association list instead of a UniqFM because
+ -- CLabel's don't have a 'Uniqueable' instance.
+ formats :: [(CLabel, StackFormat)]
+ formats = selectStackFormat live continuations
+
+ -- Do the actual CPS transform.
+ cps_procs :: [CmmTop]
+ cps_procs = map (continuationToProc formats) continuations
+
+--------------------------------------------------------------------------------
+
+-- The format for the call to a continuation
+-- The fst is the arguments that must be passed to the continuation
+-- by the continuation's caller.
+-- The snd is the live values that must be saved on stack.
+-- A Nothing indicates an ignored slot.
+-- The head of each list is the stack top or the first parameter.
+
+-- The format for live values for a particular continuation
+-- All on stack for now.
+-- Head element is the top of the stack (or just under the header).
+-- Nothing means an empty slot.
+-- Future possibilities include callee save registers (i.e. passing slots in register)
+-- and heap memory (not sure if that's usefull at all though, but it may
+-- be worth exploring the design space).
+
+continuationLabel (Continuation _ _ l _ _) = l
+data Continuation =
+ Continuation
+ Bool -- True => Function entry, False => Continuation/return point
+ [CmmStatic] -- Info table, may be empty
+ CLabel -- Used to generate both info & entry labels
+ CmmFormals -- Argument locals live on entry (C-- procedure params)
+ [BrokenBlock] -- Code, may be empty. The first block is
+ -- the entry point. The order is otherwise initially
+ -- unimportant, but at some point the code gen will
+ -- fix the order.
+
+ -- the BlockId of the first block does not give rise
+ -- to a label. To jump to the first block in a Proc,
+ -- use the appropriate CLabel.
+
+-- Describes the layout of a stack frame for a continuation
+data StackFormat
+ = StackFormat
+ (Maybe CLabel) -- The label occupying the top slot
+ WordOff -- Total frame size in words
+ [(CmmReg, WordOff)] -- local reg offsets from stack top
+
+-- A block can be a continuation of a call
+-- A block can be a continuation of another block (w/ or w/o joins)
+-- A block can be an entry to a function
+
+-----------------------------------------------------------------------------
+
+collectNonProcPointTargets ::
+ UniqSet BlockId -> BlockEnv BrokenBlock
+ -> UniqSet BlockId -> BlockId -> UniqSet BlockId
+collectNonProcPointTargets proc_points blocks current_targets block =
+ if sizeUniqSet current_targets == sizeUniqSet new_targets
+ then current_targets
+ else foldl (collectNonProcPointTargets proc_points blocks) new_targets targets
+ where
+ block' = lookupWithDefaultUFM blocks (panic "TODO") block
+ targets =
+ -- Note the subtlety that since the extra branch after a call
+ -- will always be to a block that is a proc-point,
+ -- this subtraction will always remove that case
+ uniqSetToList $ (mkUniqSet $ brokenBlockTargets block') `minusUniqSet` proc_points
+ -- TODO: remove redundant uniqSetToList
+ new_targets = current_targets `unionUniqSets` (mkUniqSet targets)
+
+-- TODO: insert proc point code here
+-- * Branches and switches to proc points may cause new blocks to be created
+-- (or proc points could leave behind phantom blocks that just jump to them)
+-- * Proc points might get some live variables passed as arguments
+
+gatherBlocksIntoContinuation ::
+ UniqSet BlockId -> BlockEnv BrokenBlock
+ -> BlockId -> Continuation
+gatherBlocksIntoContinuation proc_points blocks start =
+ Continuation is_entry info_table clabel params body
+ where
+ children = (collectNonProcPointTargets proc_points blocks (unitUniqSet start) start) `delOneFromUniqSet` start
+ start_block = lookupWithDefaultUFM blocks (panic "TODO") start
+ children_blocks = map (lookupWithDefaultUFM blocks (panic "TODO")) (uniqSetToList children)
+ body = start_block : children_blocks
+ info_table = [] -- TODO
+ start_block_entry = brokenBlockEntry start_block
+ is_entry = case start_block_entry of
+ FunctionEntry _ _ -> True
+ _ -> False
+ clabel = case start_block_entry of
+ FunctionEntry label _ -> label
+ _ -> mkReturnPtLabel $ getUnique start
+ params = case start_block_entry of
+ FunctionEntry _ args -> args
+ ContinuationEntry args -> args
+ ControlEntry -> [] -- TODO: it's a proc-point, we could pass lives in parameter registers
+
+--------------------------------------------------------------------------------
+-- For now just select the continuation orders in the order they are in the set with no gaps
+
+selectStackFormat :: BlockEnv CmmLive -> [Continuation] -> [(CLabel, StackFormat)]
+selectStackFormat live continuations =
+ map (\c -> (continuationLabel c, selectStackFormat' c)) continuations
+ where
+ selectStackFormat' (Continuation True info_table label formals blocks) =
+ StackFormat (Just label) 0 []
+ selectStackFormat' (Continuation False info_table label formals blocks) =
+ -- TODO: assumes the first block is the entry block
+ let ident = brokenBlockId $ head blocks -- TODO: CLabel isn't a uniquable, but we need a better way than this
+ in live_to_format label formals $ lookupWithDefaultUFM live unknown_block ident
+
+ live_to_format :: CLabel -> CmmFormals -> CmmLive -> StackFormat
+ live_to_format label formals live =
+ foldl extend_format
+ (StackFormat (Just label) retAddrSizeW [])
+ (uniqSetToList (live `minusUniqSet` mkUniqSet (cmmFormalsToLiveLocals formals)))
+
+ extend_format :: StackFormat -> LocalReg -> StackFormat
+ extend_format (StackFormat label size offsets) reg =
+ StackFormat label (slot_size reg + size) ((CmmLocal reg, size) : offsets)
+
+ slot_size :: LocalReg -> Int
+ slot_size reg = ((machRepByteWidth (localRegRep reg) - 1) `div` wORD_SIZE) + 1
+
+ unknown_block = panic "unknown BlockId in selectStackFormat"
+
+continuationToProc :: [(CLabel, StackFormat)] -> Continuation -> CmmTop
+continuationToProc formats (Continuation is_entry info label formals blocks) =
+ CmmProc info label formals (map (continuationToProc' label formats) blocks)
+ where
+ continuationToProc' :: CLabel -> [(CLabel, StackFormat)] -> BrokenBlock
+ -> CmmBasicBlock
+ continuationToProc' curr_ident formats (BrokenBlock ident entry stmts _ exit) =
+ BasicBlock ident (prefix++stmts++postfix)
+ where
+ curr_format = maybe unknown_block id $ lookup curr_ident formats
+ unknown_block = panic "unknown BlockId in continuationToProc"
+ prefix = case entry of
+ ControlEntry -> []
+ FunctionEntry _ _ -> []
+ ContinuationEntry formals ->
+ unpack_continuation curr_format
+ postfix = case exit of
+ FinalBranch next -> [CmmBranch next]
+ FinalSwitch expr targets -> [CmmSwitch expr targets]
+ FinalReturn arguments ->
+ exit_function curr_format
+ (CmmLoad (CmmReg spReg) wordRep)
+ arguments
+ FinalJump target arguments ->
+ exit_function curr_format target arguments
+ FinalCall next (CmmForeignCall target CmmCallConv)
+ results arguments ->
+ pack_continuation curr_format cont_format ++
+ [CmmJump target arguments]
+ where
+ cont_format = maybe unknown_block id $
+ lookup (mkReturnPtLabel $ getUnique next) formats
+ FinalCall next _ results arguments -> panic "unimplemented CmmCall"
+
+--------------------------------------------------------------------------------
+-- Functions that generate CmmStmt sequences
+-- for packing/unpacking continuations
+-- and entering/exiting functions
+
+exit_function :: StackFormat -> CmmExpr -> CmmActuals -> [CmmStmt]
+exit_function (StackFormat curr_id curr_frame_size curr_offsets) target arguments
+ = adjust_spReg ++ jump where
+ adjust_spReg =
+ if curr_frame_size == 0
+ then []
+ else [CmmAssign spReg
+ (CmmRegOff spReg (curr_frame_size*wORD_SIZE))]
+ jump = [CmmJump target arguments]
+
+enter_function :: WordOff -> [CmmStmt]
+enter_function max_frame_size
+ = check_stack_limit where
+ check_stack_limit = [
+ CmmCondBranch
+ (CmmMachOp (MO_U_Lt $ cmmRegRep spReg)
+ [CmmRegOff spReg max_frame_size, CmmReg spLimReg])
+ gc_block]
+ gc_block = panic "gc_check not implemented" -- TODO: get stack and heap checks to go to same
+
+-- TODO: fix branches to proc point (we have to insert a new block to marshel the continuation)
+pack_continuation :: StackFormat -> StackFormat -> [CmmStmt]
+pack_continuation (StackFormat curr_id curr_frame_size curr_offsets)
+ (StackFormat cont_id cont_frame_size cont_offsets)
+ = save_live_values ++ set_stack_header ++ adjust_spReg where
+ -- TODO: only save variables when actually needed
+ save_live_values =
+ [CmmStore
+ (CmmRegOff
+ spReg (wORD_SIZE*(curr_frame_size - cont_frame_size + offset)))
+ (CmmReg reg)
+ | (reg, offset) <- cont_offsets]
+ needs_header =
+ case (curr_id, cont_id) of
+ (Just x, Just y) -> x /= y
+ _ -> isJust cont_id
+ set_stack_header =
+ if not needs_header
+ then []
+ else [CmmStore (CmmRegOff spReg (wORD_SIZE*(curr_frame_size - cont_frame_size))) continuation_function]
+ continuation_function = CmmLit $ CmmLabel $ fromJust cont_id
+ adjust_spReg =
+ if curr_frame_size == cont_frame_size
+ then []
+ else [CmmAssign spReg (CmmRegOff spReg ((curr_frame_size - cont_frame_size)*wORD_SIZE))]
+
+-- Lazy adjustment of stack headers assumes all blocks
+-- that could branch to eachother (i.e. control blocks)
+-- have the same stack format (this causes a problem
+-- only for proc-point).
+unpack_continuation :: StackFormat -> [CmmStmt]
+unpack_continuation (StackFormat curr_id curr_frame_size curr_offsets)
+ = load_live_values where
+ -- TODO: only save variables when actually needed
+ load_live_values =
+ [CmmAssign
+ reg
+ (CmmLoad (CmmRegOff spReg (wORD_SIZE*offset)) (cmmRegRep reg))
+ | (reg, offset) <- curr_offsets]
+
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