X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Fcmm%2FCmmCPS.hs;h=35eabb331704e26e3a83cb8468b661105e3eeb36;hp=1a0011021891c49149cf3d7fa5000b0d48cd7c87;hb=643397208b83f1654bceeef40c793f11592ef816;hpb=a962e15a9c778a47e7193bb1bd1c1c54a32ebef5 diff --git a/compiler/cmm/CmmCPS.hs b/compiler/cmm/CmmCPS.hs index 1a00110..35eabb3 100644 --- a/compiler/cmm/CmmCPS.hs +++ b/compiler/cmm/CmmCPS.hs @@ -1,413 +1,171 @@ +{-# OPTIONS_GHC -XNoMonoLocalBinds #-} +-- Norman likes local bindings +-- If this module lives on I'd like to get rid of this flag in due course + module CmmCPS ( -- | Converts C-- with full proceedures and parameters -- to a CPS transformed C-- with the stack made manifest. - cmmCPS + -- Well, sort of. + protoCmmCPS ) where -#include "HsVersions.h" - +import CLabel import Cmm -import CmmLint -import PprCmm - -import CmmLive -import CmmBrokenBlock +import CmmDecl +import CmmBuildInfoTables +import CmmCommonBlockElim import CmmProcPoint -import CmmCallConv -import CmmCPSGen -import CmmInfo -import CmmUtils - -import ClosureInfo -import MachOp -import ForeignCall -import CLabel -import SMRep -import Constants +import CmmSpillReload +import CmmStackLayout +import OptimizationFuel import DynFlags import ErrUtils -import Maybes +import HscTypes +import Data.Maybe +import Control.Monad +import Data.Map (Map) +import qualified Data.Map as Map import Outputable -import UniqSupply -import UniqFM -import UniqSet -import Unique - -import Monad -import IO -import Data.List +import StaticFlags ----------------------------------------------------------------------------- -- |Top level driver for the CPS pass ----------------------------------------------------------------------------- -cmmCPS :: DynFlags -- ^ Dynamic flags: -dcmm-lint -ddump-cps-cmm - -> [GenCmm CmmStatic CmmInfo CmmStmt] -- ^ Input C-- with Proceedures - -> IO [GenCmm CmmStatic [CmmStatic] CmmStmt] -- ^ Output CPS transformed C-- -cmmCPS dflags abstractC = do - when (dopt Opt_DoCmmLinting dflags) $ - do showPass dflags "CmmLint" - case firstJust $ map cmmLint abstractC of - Just err -> do printDump err - ghcExit dflags 1 - Nothing -> return () - showPass dflags "CPS" - - -- 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 - -stg_gc_gen = mkRtsApFastLabel SLIT("gen_cg_TODO") --panic "Need the label for gc" -make_gc_block block_id fun_label formals safety = BasicBlock block_id stmts - where - stmts = [CmmCall stg_gc_gen_target [] [] safety, - CmmJump fun_expr actuals] - stg_gc_gen_target = - CmmForeignCall (CmmLit (CmmLabel stg_gc_gen)) CmmCallConv - actuals = map (\x -> (CmmReg (CmmLocal x), NoHint)) formals - fun_expr = CmmLit (CmmLabel fun_label) - -make_gc_check stack_use gc_block = - [CmmCondBranch - (CmmMachOp (MO_U_Lt $ cmmRegRep spReg) - [CmmReg stack_use, CmmReg spLimReg]) - gc_block] - -force_gc_block old_info stack_use block_id fun_label formals = - case old_info of - CmmNonInfo (Just existing) -> (old_info, [], make_gc_check stack_use existing) - CmmInfo _ (Just existing) _ _ -> (old_info, [], make_gc_check stack_use existing) - CmmNonInfo Nothing - -> (CmmNonInfo (Just block_id), - [make_gc_block block_id fun_label formals (CmmSafe NoC_SRT)], - make_gc_check stack_use block_id) - CmmInfo prof Nothing type_tag type_info - -> (CmmInfo prof (Just block_id) type_tag type_info, - [make_gc_block block_id fun_label formals (CmmSafe srt)], - make_gc_check stack_use block_id) - where - srt = case type_info of - ConstrInfo _ _ _ -> NoC_SRT - FunInfo _ srt' _ _ _ _ -> srt' - ThunkInfo _ srt' -> srt' - ThunkSelectorInfo _ srt' -> srt' - ContInfo _ srt' -> srt' - ------------------------------------------------------------------------------ --- |CPS a single CmmTop (proceedure) --- Only 'CmmProc' are transformed 'CmmData' will be left alone. ------------------------------------------------------------------------------ - -cpsProc :: UniqSupply - -> GenCmmTop CmmStatic CmmInfo CmmStmt -- ^Input proceedure - -> [GenCmmTop CmmStatic [CmmStatic] CmmStmt] -- ^Output proceedure and continuations -cpsProc uniqSupply (CmmData sec dat) = [CmmData sec dat] -cpsProc uniqSupply (CmmProc info ident params blocks) = info_procs - where - (uniqSupply1, uniqSupply2) = splitUniqSupply uniqSupply - uniques :: [[Unique]] - uniques = map uniqsFromSupply $ listSplitUniqSupply uniqSupply1 - (gc_unique:stack_use_unique:info_uniques):adaptor_uniques:block_uniques = uniques - proc_uniques = map (map uniqsFromSupply . listSplitUniqSupply) $ listSplitUniqSupply uniqSupply2 - - stack_use = CmmLocal (LocalReg stack_use_unique (cmmRegRep spReg) KindPtr) - - -- TODO: doc - forced_gc :: (CmmInfo, [CmmBasicBlock], [CmmStmt]) - forced_gc = force_gc_block info stack_use (BlockId gc_unique) ident params - (forced_info, gc_blocks, check_stmts) = forced_gc - - forced_blocks = - case blocks of - (BasicBlock id stmts) : bs -> - (BasicBlock id (check_stmts ++ stmts)) : (bs ++ gc_blocks) - [] -> [] -- If there is no code then we don't need a stack check - - forced_gc_id = case forced_info of - CmmNonInfo (Just x) -> x - CmmInfo _ (Just x) _ _ -> x - - -- Break the block at each function call. - -- The part after the function call will have to become a continuation. - broken_blocks :: ([(BlockId, ContFormat)], [BrokenBlock]) - broken_blocks = - (\x -> (concatMap fst x, concatMap snd x)) $ - zipWith3 (breakBlock [forced_gc_id]) - block_uniques - forced_blocks - (FunctionEntry forced_info ident params : - repeat ControlEntry) - - f' = selectContinuations (fst broken_blocks) - broken_blocks' = map (makeContinuationEntries f') $ - concat $ - zipWith (adaptBlockToFormat f') - adaptor_uniques - (snd broken_blocks) - - -- 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 (Either C_SRT CmmInfo)] - continuations = zipWith - (gatherBlocksIntoContinuation live proc_points block_env) - (uniqSetToList proc_points) - (Just forced_gc_id : repeat Nothing) {-dead-} - - -- Select the stack format on entry to each continuation. - -- Return the max stack offset and an association list - -- - -- This is an association list instead of a UniqFM because - -- CLabel's don't have a 'Uniqueable' instance. - formats :: [(CLabel, -- key - (CmmFormals, -- arguments - Maybe CLabel, -- label in top slot - [Maybe LocalReg]))] -- slots - formats = selectContinuationFormat live continuations - - -- Do a little meta-processing on the stack formats such as - -- getting the individual frame sizes and the maximum frame size - formats' :: (WordOff, [(CLabel, ContinuationFormat)]) - formats' = processFormats formats continuations - - -- Update the info table data on the continuations with - -- the selected stack formats. - continuations' :: [Continuation CmmInfo] - continuations' = map (applyContinuationFormat (snd formats')) continuations - - -- Do the actual CPS transform. - cps_procs :: [CmmTop] - cps_procs = zipWith (continuationToProc formats' stack_use) proc_uniques continuations' - - -- Convert the info tables from CmmInfo to [CmmStatic] - -- We might want to put this in another pass eventually - info_procs :: [RawCmmTop] - info_procs = concat (zipWith mkInfoTable info_uniques cps_procs) - ------------------------------------------------------------------------------ - -collectNonProcPointTargets :: - UniqSet BlockId -> BlockEnv BrokenBlock - -> UniqSet BlockId -> [BlockId] -> UniqSet BlockId -collectNonProcPointTargets proc_points blocks current_targets new_blocks = - if sizeUniqSet current_targets == sizeUniqSet new_targets - then current_targets - else foldl - (collectNonProcPointTargets proc_points blocks) - new_targets - (map (:[]) targets) - where - blocks' = map (lookupWithDefaultUFM blocks (panic "TODO")) new_blocks - 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 $ (unionManyUniqSets $ map (mkUniqSet . brokenBlockTargets) blocks') - `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 :: - BlockEntryLiveness -> UniqSet BlockId -> BlockEnv BrokenBlock - -> BlockId -> Maybe BlockId -> Continuation (Either C_SRT CmmInfo) -gatherBlocksIntoContinuation live proc_points blocks start gc = - Continuation info_table clabel params is_gc_cont body - where - --start_and_gc = [start] -- : maybeToList gc - --children = (collectNonProcPointTargets proc_points blocks (mkUniqSet start_and_gc) start_and_gc) `minusUniqSet` (mkUniqSet start_and_gc) - children = (collectNonProcPointTargets proc_points blocks (unitUniqSet start) [start]) `minusUniqSet` (unitUniqSet start) - start_block = lookupWithDefaultUFM blocks (panic "TODO") start - unknown_block = panic "unknown block in gatherBlocksIntoContinuation" - --gc_block = map (lookupWithDefaultUFM blocks (panic "TODO)")) - -- (maybeToList gc) - children_blocks = map (lookupWithDefaultUFM blocks (panic "TODO")) (uniqSetToList children) - body = start_block : {-gc_block ++ -} children_blocks - - -- We can't properly annotate the continuation's stack parameters - -- at this point because this is before stack selection - -- but we want to keep the C_SRT around so we use 'Either'. - info_table = case start_block_entry of - FunctionEntry info _ _ -> Right info - ContinuationEntry _ srt _ -> Left srt - ControlEntry -> Right (CmmNonInfo Nothing) - - is_gc_cont = case start_block_entry of - FunctionEntry _ _ _ -> False - ContinuationEntry _ _ gc_cont -> gc_cont - ControlEntry -> False - - start_block_entry = brokenBlockEntry start_block - 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 -> - uniqSetToList $ - lookupWithDefaultUFM live unknown_block start - -- it's a proc-point, pass lives in parameter registers - --------------------------------------------------------------------------------- --- For now just select the continuation orders in the order they are in the set with no gaps - -selectContinuationFormat :: BlockEnv CmmLive - -> [Continuation (Either C_SRT CmmInfo)] - -> [(CLabel, (CmmFormals, Maybe CLabel, [Maybe LocalReg]))] -selectContinuationFormat live continuations = - map (\c -> (continuationLabel c, selectContinuationFormat' c)) continuations - where - -- User written continuations - selectContinuationFormat' (Continuation - (Right (CmmInfo _ _ _ (ContInfo format srt))) - label formals _ _) = - (formals, Just label, format) - -- Either user written non-continuation code - -- or CPS generated proc-points - selectContinuationFormat' (Continuation (Right _) _ formals _ _) = - (formals, Nothing, []) - -- CPS generated continuations - selectContinuationFormat' (Continuation (Left srt) 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 (formals, - Just label, - map Just $ uniqSetToList $ - lookupWithDefaultUFM live unknown_block ident) - - unknown_block = panic "unknown BlockId in selectContinuationFormat" - -processFormats :: [(CLabel, (CmmFormals, Maybe CLabel, [Maybe LocalReg]))] - -> [Continuation (Either C_SRT CmmInfo)] - -> (WordOff, [(CLabel, ContinuationFormat)]) -processFormats formats continuations = (max_size, formats') - where - max_size = maximum $ - 0 : map (continuationMaxStack formats') continuations - formats' = map make_format formats - make_format (label, (formals, top, stack)) = - (label, - ContinuationFormat { - continuation_formals = formals, - continuation_label = top, - continuation_frame_size = stack_size stack + - if isJust top - then label_size - else 0, - continuation_stack = stack }) - - -- TODO: get rid of "+ 1" etc. - label_size = 1 :: WordOff - - stack_size [] = 0 - stack_size (Nothing:formats) = 1 + stack_size formats -- one dead word - stack_size (Just reg:formats) = width + stack_size formats - where - width = machRepByteWidth (localRegRep reg) `quot` wORD_SIZE - -- TODO: it would be better if we had a machRepWordWidth - -continuationMaxStack :: [(CLabel, ContinuationFormat)] - -> Continuation a - -> WordOff -continuationMaxStack _ (Continuation _ _ _ True _) = 0 -continuationMaxStack formats (Continuation _ label _ False blocks) = - max_arg_size + continuation_frame_size stack_format - where - stack_format = maybe unknown_format id $ lookup label formats - unknown_format = panic "Unknown format in continuationMaxStack" - - max_arg_size = maximum $ 0 : map block_max_arg_size blocks - - block_max_arg_size block = - maximum (final_arg_size (brokenBlockExit block) : - map stmt_arg_size (brokenBlockStmts block)) - - final_arg_size (FinalReturn args) = - argumentsSize (cmmExprRep . fst) args - final_arg_size (FinalJump _ args) = - argumentsSize (cmmExprRep . fst) args - final_arg_size (FinalCall next _ _ args _ True) = 0 - final_arg_size (FinalCall next _ _ args _ False) = - -- We have to account for the stack used when we build a frame - -- for the *next* continuation from *this* continuation - argumentsSize (cmmExprRep . fst) args + - continuation_frame_size next_format - where - next_format = maybe unknown_format id $ lookup next' formats - next' = mkReturnPtLabel $ getUnique next - - final_arg_size _ = 0 - - stmt_arg_size (CmmJump _ args) = - argumentsSize (cmmExprRep . fst) args - stmt_arg_size (CmmCall _ _ _ (CmmSafe _)) = - panic "Safe call in processFormats" - stmt_arg_size (CmmReturn _) = - panic "CmmReturn in processFormats" - stmt_arg_size _ = 0 - ------------------------------------------------------------------------------ -applyContinuationFormat :: [(CLabel, ContinuationFormat)] - -> Continuation (Either C_SRT CmmInfo) - -> Continuation CmmInfo - --- User written continuations -applyContinuationFormat formats (Continuation - (Right (CmmInfo prof gc tag (ContInfo _ srt))) - label formals is_gc blocks) = - Continuation (CmmInfo prof gc tag (ContInfo format srt)) - label formals is_gc blocks - where - format = continuation_stack $ maybe unknown_block id $ lookup label formats - unknown_block = panic "unknown BlockId in applyContinuationFormat" - --- Either user written non-continuation code or CPS generated proc-point -applyContinuationFormat formats (Continuation - (Right info) label formals is_gc blocks) = - Continuation info label formals is_gc blocks - --- CPS generated continuations -applyContinuationFormat formats (Continuation - (Left srt) label formals is_gc blocks) = - Continuation (CmmInfo prof gc tag (ContInfo (continuation_stack $ format) srt)) - label formals is_gc blocks - where - gc = Nothing -- Generated continuations never need a stack check - -- TODO prof: this is the same as the current implementation - -- but I think it could be improved - prof = ProfilingInfo zeroCLit zeroCLit - tag = rET_SMALL -- cmmToRawCmm may convert it to rET_BIG - format = maybe unknown_block id $ lookup label formats - unknown_block = panic "unknown BlockId in applyContinuationFormat" - +-- 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. +protoCmmCPS :: HscEnv -- Compilation env including + -- dynamic flags: -dcmm-lint -ddump-cps-cmm + -> (TopSRT, [Cmm]) -- SRT table and accumulating list of compiled procs + -> Cmm -- Input C-- with Procedures + -> IO (TopSRT, [Cmm]) -- Output CPS transformed C-- +protoCmmCPS hsc_env (topSRT, rst) (Cmm tops) = + do let dflags = hsc_dflags hsc_env + showPass dflags "CPSZ" + (cafEnvs, tops) <- liftM unzip $ mapM (cpsTop hsc_env) tops + let topCAFEnv = mkTopCAFInfo (concat cafEnvs) + (topSRT, tops) <- foldM (toTops hsc_env topCAFEnv) (topSRT, []) tops + let cmms = Cmm (reverse (concat tops)) + dumpIfSet_dyn dflags Opt_D_dump_cps_cmm "Post CPS Cmm" (ppr cmms) + return (topSRT, cmms : rst) + +{- [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. +-} + +-- 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 + +cpsTop :: HscEnv -> CmmTop -> IO ([(CLabel, CAFSet)], [(CAFSet, CmmTop)]) +cpsTop _ p@(CmmData {}) = return ([], [(Map.empty, p)]) +cpsTop hsc_env (CmmProc h@(TopInfo {stack_info=StackInfo {arg_space=entry_off}}) l g) = + do + -- Why bother doing these early: dualLivenessWithInsertion, + -- insertLateReloads, rewriteAssignments? + + ----------- Eliminate common blocks ------------------- + g <- return $ elimCommonBlocks g + dump Opt_D_dump_cmmz_cbe "Post common block elimination" g + -- Any work storing block Labels must be performed _after_ elimCommonBlocks + + ----------- Proc points ------------------- + let callPPs = callProcPoints g + procPoints <- run $ minimalProcPointSet callPPs g + g <- run $ addProcPointProtocols callPPs procPoints g + dump Opt_D_dump_cmmz_proc "Post Proc Points Added" g + + ----------- Spills and reloads ------------------- + g <- run $ dualLivenessWithInsertion procPoints g + dump Opt_D_dump_cmmz_spills "Post spills and reloads" g + + ----------- Sink and inline assignments ------------------- + g <- runOptimization $ rewriteAssignments g + dump Opt_D_dump_cmmz_rewrite "Post rewrite assignments" g + + ----------- Eliminate dead assignments ------------------- + -- Remove redundant reloads (and any other redundant asst) + g <- runOptimization $ removeDeadAssignmentsAndReloads procPoints g + dump Opt_D_dump_cmmz_dead "Post Dead Assignment Elimination" g + + ----------- Zero dead stack slots (Debug only) --------------- + -- Debugging: stubbing slots on death can cause crashes early + g <- if opt_StubDeadValues + then run $ stubSlotsOnDeath g + else return g + dump Opt_D_dump_cmmz_stub "Post stub dead stack slots" g + + --------------- Stack layout ---------------- + slotEnv <- run $ liveSlotAnal g + let spEntryMap = getSpEntryMap entry_off g + mbpprTrace "live slot analysis results: " (ppr slotEnv) $ return () + let areaMap = layout procPoints spEntryMap slotEnv entry_off g + mbpprTrace "areaMap" (ppr areaMap) $ return () + + ------------ Manifest the stack pointer -------- + g <- run $ manifestSP spEntryMap areaMap entry_off g + dump Opt_D_dump_cmmz_sp "Post manifestSP" g + -- UGH... manifestSP can require updates to the procPointMap. + -- We can probably do something quicker here for the update... + + ------------- Split into separate procedures ------------ + procPointMap <- run $ procPointAnalysis procPoints g + dump Opt_D_dump_cmmz_procmap "procpoint map" procPointMap + gs <- run $ splitAtProcPoints l callPPs procPoints procPointMap + (CmmProc h l g) + mapM_ (dump Opt_D_dump_cmmz_split "Post splitting") gs + + ------------- More CAFs and foreign calls ------------ + cafEnv <- run $ cafAnal g + let localCAFs = catMaybes $ map (localCAFInfo cafEnv) gs + mbpprTrace "localCAFs" (ppr localCAFs) $ return () + + gs <- run $ mapM (lowerSafeForeignCalls areaMap) gs + mapM_ (dump Opt_D_dump_cmmz_lower "Post lowerSafeForeignCalls") gs + + -- NO MORE GRAPH TRANSFORMATION AFTER HERE -- JUST MAKING INFOTABLES + gs <- return $ map (setInfoTableStackMap slotEnv areaMap) gs + mapM_ (dump Opt_D_dump_cmmz_info "after setInfoTableStackMap") gs + gs <- return $ map (bundleCAFs cafEnv) gs + mapM_ (dump Opt_D_dump_cmmz_cafs "after bundleCAFs") gs + return (localCAFs, gs) + where dflags = hsc_dflags hsc_env + mbpprTrace x y z = if dopt Opt_D_dump_cmmz dflags then pprTrace x y z else z + dump f 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 f txt (ppr g) + when (not (dopt f dflags)) $ + dumpIfSet_dyn dflags Opt_D_dump_cmmz txt (ppr g) + -- 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) + +-- 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. +toTops :: HscEnv -> Map CLabel CAFSet -> (TopSRT, [[CmmTop]]) + -> [(CAFSet, CmmTop)] -> IO (TopSRT, [[CmmTop]]) +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)