----------------------------------------------------------------------------- -- -- Code generator utilities; mostly monadic -- -- (c) The University of Glasgow 2004-2006 -- ----------------------------------------------------------------------------- module StgCmmUtils ( cgLit, mkSimpleLit, emitDataLits, mkDataLits, emitRODataLits, mkRODataLits, emitRtsCall, emitRtsCallWithVols, emitRtsCallWithResult, assignTemp, newTemp, withTemp, newUnboxedTupleRegs, mkMultiAssign, mkCmmSwitch, mkCmmLitSwitch, emitSwitch, tagToClosure, mkTaggedObjectLoad, callerSaveVolatileRegs, get_GlobalReg_addr, cmmAndWord, cmmOrWord, cmmNegate, cmmEqWord, cmmNeWord, cmmUGtWord, cmmOffsetExprW, cmmOffsetExprB, cmmRegOffW, cmmRegOffB, cmmLabelOffW, cmmLabelOffB, cmmOffsetW, cmmOffsetB, cmmOffsetLitW, cmmOffsetLitB, cmmLoadIndexW, cmmConstrTag, cmmConstrTag1, cmmUntag, cmmIsTagged, cmmGetTag, addToMem, addToMemE, addToMemLbl, mkWordCLit, mkStringCLit, mkByteStringCLit, packHalfWordsCLit, blankWord, getSRTInfo, clHasCafRefs, srt_escape ) where #include "HsVersions.h" #include "../includes/stg/MachRegs.h" import StgCmmMonad import StgCmmClosure import BlockId import Cmm import MkZipCfgCmm import CLabel import CmmUtils import PprCmm ( {- instances -} ) import ForeignCall import IdInfo import Type import TyCon import Constants import SMRep import StgSyn ( SRT(..) ) import Literal import Digraph import ListSetOps import Util import Unique import DynFlags import FastString import Outputable import Data.Char import Data.Bits import Data.Word import Data.Maybe ------------------------------------------------------------------------- -- -- Literals -- ------------------------------------------------------------------------- cgLit :: Literal -> FCode CmmLit cgLit (MachStr s) = mkByteStringCLit (bytesFS s) -- not unpackFS; we want the UTF-8 byte stream. cgLit other_lit = return (mkSimpleLit other_lit) mkSimpleLit :: Literal -> CmmLit mkSimpleLit (MachChar c) = CmmInt (fromIntegral (ord c)) wordWidth mkSimpleLit MachNullAddr = zeroCLit mkSimpleLit (MachInt i) = CmmInt i wordWidth mkSimpleLit (MachInt64 i) = CmmInt i W64 mkSimpleLit (MachWord i) = CmmInt i wordWidth mkSimpleLit (MachWord64 i) = CmmInt i W64 mkSimpleLit (MachFloat r) = CmmFloat r W32 mkSimpleLit (MachDouble r) = CmmFloat r W64 mkSimpleLit (MachLabel fs ms fod) = CmmLabel (mkForeignLabel fs ms is_dyn fod) where is_dyn = False -- ToDo: fix me mkSimpleLit other = pprPanic "mkSimpleLit" (ppr other) mkLtOp :: Literal -> MachOp -- On signed literals we must do a signed comparison mkLtOp (MachInt _) = MO_S_Lt wordWidth mkLtOp (MachFloat _) = MO_F_Lt W32 mkLtOp (MachDouble _) = MO_F_Lt W64 mkLtOp lit = MO_U_Lt (typeWidth (cmmLitType (mkSimpleLit lit))) -- ToDo: seems terribly indirect! --------------------------------------------------- -- -- Cmm data type functions -- --------------------------------------------------- -- The "B" variants take byte offsets cmmRegOffB :: CmmReg -> ByteOff -> CmmExpr cmmRegOffB = cmmRegOff cmmOffsetB :: CmmExpr -> ByteOff -> CmmExpr cmmOffsetB = cmmOffset cmmOffsetExprB :: CmmExpr -> CmmExpr -> CmmExpr cmmOffsetExprB = cmmOffsetExpr cmmLabelOffB :: CLabel -> ByteOff -> CmmLit cmmLabelOffB = cmmLabelOff cmmOffsetLitB :: CmmLit -> ByteOff -> CmmLit cmmOffsetLitB = cmmOffsetLit ----------------------- -- The "W" variants take word offsets cmmOffsetExprW :: CmmExpr -> CmmExpr -> CmmExpr -- The second arg is a *word* offset; need to change it to bytes cmmOffsetExprW e (CmmLit (CmmInt n _)) = cmmOffsetW e (fromInteger n) cmmOffsetExprW e wd_off = cmmIndexExpr wordWidth e wd_off cmmOffsetW :: CmmExpr -> WordOff -> CmmExpr cmmOffsetW e n = cmmOffsetB e (wORD_SIZE * n) cmmRegOffW :: CmmReg -> WordOff -> CmmExpr cmmRegOffW reg wd_off = cmmRegOffB reg (wd_off * wORD_SIZE) cmmOffsetLitW :: CmmLit -> WordOff -> CmmLit cmmOffsetLitW lit wd_off = cmmOffsetLitB lit (wORD_SIZE * wd_off) cmmLabelOffW :: CLabel -> WordOff -> CmmLit cmmLabelOffW lbl wd_off = cmmLabelOffB lbl (wORD_SIZE * wd_off) cmmLoadIndexW :: CmmExpr -> Int -> CmmType -> CmmExpr cmmLoadIndexW base off ty = CmmLoad (cmmOffsetW base off) ty ----------------------- cmmULtWord, cmmUGeWord, cmmUGtWord, cmmSubWord, cmmNeWord, cmmEqWord, cmmOrWord, cmmAndWord :: CmmExpr -> CmmExpr -> CmmExpr cmmOrWord e1 e2 = CmmMachOp mo_wordOr [e1, e2] cmmAndWord e1 e2 = CmmMachOp mo_wordAnd [e1, e2] cmmNeWord e1 e2 = CmmMachOp mo_wordNe [e1, e2] cmmEqWord e1 e2 = CmmMachOp mo_wordEq [e1, e2] cmmULtWord e1 e2 = CmmMachOp mo_wordULt [e1, e2] cmmUGeWord e1 e2 = CmmMachOp mo_wordUGe [e1, e2] cmmUGtWord e1 e2 = CmmMachOp mo_wordUGt [e1, e2] --cmmShlWord e1 e2 = CmmMachOp mo_wordShl [e1, e2] --cmmUShrWord e1 e2 = CmmMachOp mo_wordUShr [e1, e2] cmmSubWord e1 e2 = CmmMachOp mo_wordSub [e1, e2] cmmNegate :: CmmExpr -> CmmExpr cmmNegate (CmmLit (CmmInt n rep)) = CmmLit (CmmInt (-n) rep) cmmNegate e = CmmMachOp (MO_S_Neg (cmmExprWidth e)) [e] blankWord :: CmmStatic blankWord = CmmUninitialised wORD_SIZE -- Tagging -- -- Tag bits mask --cmmTagBits = CmmLit (mkIntCLit tAG_BITS) cmmTagMask, cmmPointerMask :: CmmExpr cmmTagMask = CmmLit (mkIntCLit tAG_MASK) cmmPointerMask = CmmLit (mkIntCLit (complement tAG_MASK)) -- Used to untag a possibly tagged pointer -- A static label need not be untagged cmmUntag, cmmGetTag :: CmmExpr -> CmmExpr cmmUntag e@(CmmLit (CmmLabel _)) = e -- Default case cmmUntag e = (e `cmmAndWord` cmmPointerMask) cmmGetTag e = (e `cmmAndWord` cmmTagMask) -- Test if a closure pointer is untagged cmmIsTagged :: CmmExpr -> CmmExpr cmmIsTagged e = (e `cmmAndWord` cmmTagMask) `cmmNeWord` CmmLit zeroCLit cmmConstrTag, cmmConstrTag1 :: CmmExpr -> CmmExpr cmmConstrTag e = (e `cmmAndWord` cmmTagMask) `cmmSubWord` (CmmLit (mkIntCLit 1)) -- Get constructor tag, but one based. cmmConstrTag1 e = e `cmmAndWord` cmmTagMask ----------------------- -- Making literals mkWordCLit :: StgWord -> CmmLit mkWordCLit wd = CmmInt (fromIntegral wd) wordWidth packHalfWordsCLit :: (Integral a, Integral b) => a -> b -> CmmLit -- Make a single word literal in which the lower_half_word is -- at the lower address, and the upper_half_word is at the -- higher address -- ToDo: consider using half-word lits instead -- but be careful: that's vulnerable when reversed packHalfWordsCLit lower_half_word upper_half_word #ifdef WORDS_BIGENDIAN = mkWordCLit ((fromIntegral lower_half_word `shiftL` hALF_WORD_SIZE_IN_BITS) .|. fromIntegral upper_half_word) #else = mkWordCLit ((fromIntegral lower_half_word) .|. (fromIntegral upper_half_word `shiftL` hALF_WORD_SIZE_IN_BITS)) #endif -------------------------------------------------------------------------- -- -- Incrementing a memory location -- -------------------------------------------------------------------------- addToMemLbl :: CmmType -> CLabel -> Int -> CmmAGraph addToMemLbl rep lbl n = addToMem rep (CmmLit (CmmLabel lbl)) n addToMem :: CmmType -- rep of the counter -> CmmExpr -- Address -> Int -- What to add (a word) -> CmmAGraph addToMem rep ptr n = addToMemE rep ptr (CmmLit (CmmInt (toInteger n) (typeWidth rep))) addToMemE :: CmmType -- rep of the counter -> CmmExpr -- Address -> CmmExpr -- What to add (a word-typed expression) -> CmmAGraph addToMemE rep ptr n = mkStore ptr (CmmMachOp (MO_Add (typeWidth rep)) [CmmLoad ptr rep, n]) ------------------------------------------------------------------------- -- -- Loading a field from an object, -- where the object pointer is itself tagged -- ------------------------------------------------------------------------- mkTaggedObjectLoad :: LocalReg -> LocalReg -> WordOff -> DynTag -> CmmAGraph -- (loadTaggedObjectField reg base off tag) generates assignment -- reg = bitsK[ base + off - tag ] -- where K is fixed by 'reg' mkTaggedObjectLoad reg base offset tag = mkAssign (CmmLocal reg) (CmmLoad (cmmOffsetB (CmmReg (CmmLocal base)) (wORD_SIZE*offset - tag)) (localRegType reg)) ------------------------------------------------------------------------- -- -- Converting a closure tag to a closure for enumeration types -- (this is the implementation of tagToEnum#). -- ------------------------------------------------------------------------- tagToClosure :: TyCon -> CmmExpr -> CmmExpr tagToClosure tycon tag = CmmLoad (cmmOffsetExprW closure_tbl tag) bWord where closure_tbl = CmmLit (CmmLabel lbl) lbl = mkClosureTableLabel (tyConName tycon) NoCafRefs ------------------------------------------------------------------------- -- -- Conditionals and rts calls -- ------------------------------------------------------------------------- emitRtsCall :: LitString -> [(CmmExpr,ForeignHint)] -> Bool -> FCode () emitRtsCall fun args safe = emitRtsCall' [] fun args Nothing safe -- The 'Nothing' says "save all global registers" emitRtsCallWithVols :: LitString -> [(CmmExpr,ForeignHint)] -> [GlobalReg] -> Bool -> FCode () emitRtsCallWithVols fun args vols safe = emitRtsCall' [] fun args (Just vols) safe emitRtsCallWithResult :: LocalReg -> ForeignHint -> LitString -> [(CmmExpr,ForeignHint)] -> Bool -> FCode () emitRtsCallWithResult res hint fun args safe = emitRtsCall' [(res,hint)] fun args Nothing safe -- Make a call to an RTS C procedure emitRtsCall' :: [(LocalReg,ForeignHint)] -> LitString -> [(CmmExpr,ForeignHint)] -> Maybe [GlobalReg] -> Bool -- True <=> CmmSafe call -> FCode () emitRtsCall' res fun args _vols safe = --error "emitRtsCall'" do { updfr_off <- getUpdFrameOff ; emit caller_save ; emit $ call updfr_off ; emit caller_load } where call updfr_off = if safe then mkCmmCall fun_expr res' args' updfr_off else mkUnsafeCall (ForeignTarget fun_expr (ForeignConvention CCallConv arg_hints res_hints)) res' args' (args', arg_hints) = unzip args (res', res_hints) = unzip res (caller_save, caller_load) = callerSaveVolatileRegs fun_expr = mkLblExpr (mkRtsCodeLabel fun) ----------------------------------------------------------------------------- -- -- Caller-Save Registers -- ----------------------------------------------------------------------------- -- Here we generate the sequence of saves/restores required around a -- foreign call instruction. -- TODO: reconcile with includes/Regs.h -- * Regs.h claims that BaseReg should be saved last and loaded first -- * This might not have been tickled before since BaseReg is callee save -- * Regs.h saves SparkHd, ParkT1, SparkBase and SparkLim callerSaveVolatileRegs :: (CmmAGraph, CmmAGraph) callerSaveVolatileRegs = (caller_save, caller_load) where caller_save = catAGraphs (map callerSaveGlobalReg regs_to_save) caller_load = catAGraphs (map callerRestoreGlobalReg regs_to_save) system_regs = [ Sp,SpLim,Hp,HpLim,CurrentTSO,CurrentNursery {- ,SparkHd,SparkTl,SparkBase,SparkLim -} , BaseReg ] regs_to_save = filter callerSaves system_regs callerSaveGlobalReg reg = mkStore (get_GlobalReg_addr reg) (CmmReg (CmmGlobal reg)) callerRestoreGlobalReg reg = mkAssign (CmmGlobal reg) (CmmLoad (get_GlobalReg_addr reg) (globalRegType reg)) -- ----------------------------------------------------------------------------- -- Global registers -- We map STG registers onto appropriate CmmExprs. Either they map -- to real machine registers or stored as offsets from BaseReg. Given -- a GlobalReg, get_GlobalReg_addr always produces the -- register table address for it. -- (See also get_GlobalReg_reg_or_addr in MachRegs) get_GlobalReg_addr :: GlobalReg -> CmmExpr get_GlobalReg_addr BaseReg = regTableOffset 0 get_GlobalReg_addr mid = get_Regtable_addr_from_offset (globalRegType mid) (baseRegOffset mid) -- Calculate a literal representing an offset into the register table. -- Used when we don't have an actual BaseReg to offset from. regTableOffset :: Int -> CmmExpr regTableOffset n = CmmLit (CmmLabelOff mkMainCapabilityLabel (oFFSET_Capability_r + n)) get_Regtable_addr_from_offset :: CmmType -> Int -> CmmExpr get_Regtable_addr_from_offset _rep offset = #ifdef REG_Base CmmRegOff (CmmGlobal BaseReg) offset #else regTableOffset offset #endif -- | Returns 'True' if this global register is stored in a caller-saves -- machine register. callerSaves :: GlobalReg -> Bool #ifdef CALLER_SAVES_Base callerSaves BaseReg = True #endif #ifdef CALLER_SAVES_Sp callerSaves Sp = True #endif #ifdef CALLER_SAVES_SpLim callerSaves SpLim = True #endif #ifdef CALLER_SAVES_Hp callerSaves Hp = True #endif #ifdef CALLER_SAVES_HpLim callerSaves HpLim = True #endif #ifdef CALLER_SAVES_CurrentTSO callerSaves CurrentTSO = True #endif #ifdef CALLER_SAVES_CurrentNursery callerSaves CurrentNursery = True #endif callerSaves _ = False -- ----------------------------------------------------------------------------- -- Information about global registers baseRegOffset :: GlobalReg -> Int baseRegOffset Sp = oFFSET_StgRegTable_rSp baseRegOffset SpLim = oFFSET_StgRegTable_rSpLim baseRegOffset (LongReg 1) = oFFSET_StgRegTable_rL1 baseRegOffset Hp = oFFSET_StgRegTable_rHp baseRegOffset HpLim = oFFSET_StgRegTable_rHpLim baseRegOffset CurrentTSO = oFFSET_StgRegTable_rCurrentTSO baseRegOffset CurrentNursery = oFFSET_StgRegTable_rCurrentNursery baseRegOffset HpAlloc = oFFSET_StgRegTable_rHpAlloc baseRegOffset GCEnter1 = oFFSET_stgGCEnter1 baseRegOffset GCFun = oFFSET_stgGCFun baseRegOffset reg = pprPanic "baseRegOffset:" (ppr reg) ------------------------------------------------------------------------- -- -- Strings generate a top-level data block -- ------------------------------------------------------------------------- emitDataLits :: CLabel -> [CmmLit] -> FCode () -- Emit a data-segment data block emitDataLits lbl lits = emitData Data (CmmDataLabel lbl : map CmmStaticLit lits) mkDataLits :: CLabel -> [CmmLit] -> GenCmmTop CmmStatic info stmt -- Emit a data-segment data block mkDataLits lbl lits = CmmData Data (CmmDataLabel lbl : map CmmStaticLit lits) emitRODataLits :: CLabel -> [CmmLit] -> FCode () -- Emit a read-only data block emitRODataLits lbl lits = emitData section (CmmDataLabel lbl : map CmmStaticLit lits) where section | any needsRelocation lits = RelocatableReadOnlyData | otherwise = ReadOnlyData needsRelocation (CmmLabel _) = True needsRelocation (CmmLabelOff _ _) = True needsRelocation _ = False mkRODataLits :: CLabel -> [CmmLit] -> GenCmmTop CmmStatic info stmt mkRODataLits lbl lits = CmmData section (CmmDataLabel lbl : map CmmStaticLit lits) where section | any needsRelocation lits = RelocatableReadOnlyData | otherwise = ReadOnlyData needsRelocation (CmmLabel _) = True needsRelocation (CmmLabelOff _ _) = True needsRelocation _ = False mkStringCLit :: String -> FCode CmmLit -- Make a global definition for the string, -- and return its label mkStringCLit str = mkByteStringCLit (map (fromIntegral . ord) str) mkByteStringCLit :: [Word8] -> FCode CmmLit mkByteStringCLit bytes = do { uniq <- newUnique ; let lbl = mkStringLitLabel uniq ; emitData ReadOnlyData [CmmDataLabel lbl, CmmString bytes] ; return (CmmLabel lbl) } ------------------------------------------------------------------------- -- -- Assigning expressions to temporaries -- ------------------------------------------------------------------------- assignTemp :: CmmExpr -> FCode LocalReg -- Make sure the argument is in a local register assignTemp (CmmReg (CmmLocal reg)) = return reg assignTemp e = do { uniq <- newUnique ; let reg = LocalReg uniq (cmmExprType e) ; emit (mkAssign (CmmLocal reg) e) ; return reg } newTemp :: CmmType -> FCode LocalReg newTemp rep = do { uniq <- newUnique ; return (LocalReg uniq rep) } newUnboxedTupleRegs :: Type -> FCode ([LocalReg], [ForeignHint]) -- Choose suitable local regs to use for the components -- of an unboxed tuple that we are about to return to -- the Sequel. If the Sequel is a joint point, using the -- regs it wants will save later assignments. newUnboxedTupleRegs res_ty = ASSERT( isUnboxedTupleType res_ty ) do { sequel <- getSequel ; regs <- choose_regs sequel ; ASSERT( regs `equalLength` reps ) return (regs, map primRepForeignHint reps) } where ty_args = tyConAppArgs (repType res_ty) reps = [ rep | ty <- ty_args , let rep = typePrimRep ty , not (isVoidRep rep) ] choose_regs (AssignTo regs _) = return regs choose_regs _other = mapM (newTemp . primRepCmmType) reps ------------------------------------------------------------------------- -- mkMultiAssign ------------------------------------------------------------------------- mkMultiAssign :: [LocalReg] -> [CmmExpr] -> CmmAGraph -- Emit code to perform the assignments in the -- input simultaneously, using temporary variables when necessary. type Key = Int type Vrtx = (Key, Stmt) -- Give each vertex a unique number, -- for fast comparison type Stmt = (LocalReg, CmmExpr) -- r := e -- We use the strongly-connected component algorithm, in which -- * the vertices are the statements -- * an edge goes from s1 to s2 iff -- s1 assigns to something s2 uses -- that is, if s1 should *follow* s2 in the final order mkMultiAssign [] [] = mkNop mkMultiAssign [reg] [rhs] = mkAssign (CmmLocal reg) rhs mkMultiAssign regs rhss = ASSERT( equalLength regs rhss ) unscramble ([1..] `zip` (regs `zip` rhss)) unscramble :: [Vrtx] -> CmmAGraph unscramble vertices = catAGraphs (map do_component components) where edges :: [ (Vrtx, Key, [Key]) ] edges = [ (vertex, key1, edges_from stmt1) | vertex@(key1, stmt1) <- vertices ] edges_from :: Stmt -> [Key] edges_from stmt1 = [ key2 | (key2, stmt2) <- vertices, stmt1 `mustFollow` stmt2 ] components :: [SCC Vrtx] components = stronglyConnCompFromEdgedVertices edges -- do_components deal with one strongly-connected component -- Not cyclic, or singleton? Just do it do_component :: SCC Vrtx -> CmmAGraph do_component (AcyclicSCC (_,stmt)) = mk_graph stmt do_component (CyclicSCC []) = panic "do_component" do_component (CyclicSCC [(_,stmt)]) = mk_graph stmt -- Cyclic? Then go via temporaries. Pick one to -- break the loop and try again with the rest. do_component (CyclicSCC ((_,first_stmt) : rest)) = withUnique $ \u -> let (to_tmp, from_tmp) = split u first_stmt in mk_graph to_tmp <*> unscramble rest <*> mk_graph from_tmp split :: Unique -> Stmt -> (Stmt, Stmt) split uniq (reg, rhs) = ((tmp, rhs), (reg, CmmReg (CmmLocal tmp))) where rep = cmmExprType rhs tmp = LocalReg uniq rep mk_graph :: Stmt -> CmmAGraph mk_graph (reg, rhs) = mkAssign (CmmLocal reg) rhs mustFollow :: Stmt -> Stmt -> Bool (reg, _) `mustFollow` (_, rhs) = reg `regUsedIn` rhs regUsedIn :: LocalReg -> CmmExpr -> Bool reg `regUsedIn` CmmLoad e _ = reg `regUsedIn` e reg `regUsedIn` CmmReg (CmmLocal reg') = reg == reg' reg `regUsedIn` CmmRegOff (CmmLocal reg') _ = reg == reg' reg `regUsedIn` CmmMachOp _ es = any (reg `regUsedIn`) es _reg `regUsedIn` _other = False -- The CmmGlobal cases ------------------------------------------------------------------------- -- mkSwitch ------------------------------------------------------------------------- emitSwitch :: CmmExpr -- Tag to switch on -> [(ConTagZ, CmmAGraph)] -- Tagged branches -> Maybe CmmAGraph -- Default branch (if any) -> ConTagZ -> ConTagZ -- Min and Max possible values; behaviour -- outside this range is undefined -> FCode () emitSwitch tag_expr branches mb_deflt lo_tag hi_tag = do { dflags <- getDynFlags ; emit (mkCmmSwitch (via_C dflags) tag_expr branches mb_deflt lo_tag hi_tag) } where via_C dflags | HscC <- hscTarget dflags = True | otherwise = False mkCmmSwitch :: Bool -- True <=> never generate a conditional tree -> CmmExpr -- Tag to switch on -> [(ConTagZ, CmmAGraph)] -- Tagged branches -> Maybe CmmAGraph -- Default branch (if any) -> ConTagZ -> ConTagZ -- Min and Max possible values; behaviour -- outside this range is undefined -> CmmAGraph -- First, two rather common cases in which there is no work to do mkCmmSwitch _ _ [] (Just code) _ _ = code mkCmmSwitch _ _ [(_,code)] Nothing _ _ = code -- Right, off we go mkCmmSwitch via_C tag_expr branches mb_deflt lo_tag hi_tag = withFreshLabel "switch join" $ \ join_lbl -> label_default join_lbl mb_deflt $ \ mb_deflt -> label_branches join_lbl branches $ \ branches -> assignTemp' tag_expr $ \tag_expr' -> mk_switch tag_expr' (sortLe le branches) mb_deflt lo_tag hi_tag via_C -- Sort the branches before calling mk_switch <*> mkLabel join_lbl where (t1,_) `le` (t2,_) = t1 <= t2 mk_switch :: CmmExpr -> [(ConTagZ, BlockId)] -> Maybe BlockId -> ConTagZ -> ConTagZ -> Bool -> CmmAGraph -- SINGLETON TAG RANGE: no case analysis to do mk_switch _tag_expr [(tag, lbl)] _ lo_tag hi_tag _via_C | lo_tag == hi_tag = ASSERT( tag == lo_tag ) mkBranch lbl -- SINGLETON BRANCH, NO DEFAULT: no case analysis to do mk_switch _tag_expr [(_tag,lbl)] Nothing _ _ _ = mkBranch lbl -- The simplifier might have eliminated a case -- so we may have e.g. case xs of -- [] -> e -- In that situation we can be sure the (:) case -- can't happen, so no need to test -- SINGLETON BRANCH: one equality check to do mk_switch tag_expr [(tag,lbl)] (Just deflt) _ _ _ = mkCbranch cond deflt lbl where cond = cmmNeWord tag_expr (CmmLit (mkIntCLit tag)) -- We have lo_tag < hi_tag, but there's only one branch, -- so there must be a default -- ToDo: we might want to check for the two branch case, where one of -- the branches is the tag 0, because comparing '== 0' is likely to be -- more efficient than other kinds of comparison. -- DENSE TAG RANGE: use a switch statment. -- -- We also use a switch uncoditionally when compiling via C, because -- this will get emitted as a C switch statement and the C compiler -- should do a good job of optimising it. Also, older GCC versions -- (2.95 in particular) have problems compiling the complicated -- if-trees generated by this code, so compiling to a switch every -- time works around that problem. -- mk_switch tag_expr branches mb_deflt lo_tag hi_tag via_C | use_switch -- Use a switch = let find_branch :: ConTagZ -> Maybe BlockId find_branch i = case (assocMaybe branches i) of Just lbl -> Just lbl Nothing -> mb_deflt -- NB. we have eliminated impossible branches at -- either end of the range (see below), so the first -- tag of a real branch is real_lo_tag (not lo_tag). arms :: [Maybe BlockId] arms = [ find_branch i | i <- [real_lo_tag..real_hi_tag]] in mkSwitch (cmmOffset tag_expr (- real_lo_tag)) arms -- if we can knock off a bunch of default cases with one if, then do so | Just deflt <- mb_deflt, (lowest_branch - lo_tag) >= n_branches = mkCmmIfThenElse (cmmULtWord tag_expr (CmmLit (mkIntCLit lowest_branch))) (mkBranch deflt) (mk_switch tag_expr branches mb_deflt lowest_branch hi_tag via_C) | Just deflt <- mb_deflt, (hi_tag - highest_branch) >= n_branches = mkCmmIfThenElse (cmmUGtWord tag_expr (CmmLit (mkIntCLit highest_branch))) (mkBranch deflt) (mk_switch tag_expr branches mb_deflt lo_tag highest_branch via_C) | otherwise -- Use an if-tree = mkCmmIfThenElse (cmmUGeWord tag_expr (CmmLit (mkIntCLit mid_tag))) (mk_switch tag_expr hi_branches mb_deflt mid_tag hi_tag via_C) (mk_switch tag_expr lo_branches mb_deflt lo_tag (mid_tag-1) via_C) -- we test (e >= mid_tag) rather than (e < mid_tag), because -- the former works better when e is a comparison, and there -- are two tags 0 & 1 (mid_tag == 1). In this case, the code -- generator can reduce the condition to e itself without -- having to reverse the sense of the comparison: comparisons -- can't always be easily reversed (eg. floating -- pt. comparisons). where use_switch = {- pprTrace "mk_switch" ( ppr tag_expr <+> text "n_tags:" <+> int n_tags <+> text "branches:" <+> ppr (map fst branches) <+> text "n_branches:" <+> int n_branches <+> text "lo_tag:" <+> int lo_tag <+> text "hi_tag:" <+> int hi_tag <+> text "real_lo_tag:" <+> int real_lo_tag <+> text "real_hi_tag:" <+> int real_hi_tag) $ -} ASSERT( n_branches > 1 && n_tags > 1 ) n_tags > 2 && (via_C || (dense && big_enough)) -- up to 4 branches we use a decision tree, otherwise -- a switch (== jump table in the NCG). This seems to be -- optimal, and corresponds with what gcc does. big_enough = n_branches > 4 dense = n_branches > (n_tags `div` 2) n_branches = length branches -- ignore default slots at each end of the range if there's -- no default branch defined. lowest_branch = fst (head branches) highest_branch = fst (last branches) real_lo_tag | isNothing mb_deflt = lowest_branch | otherwise = lo_tag real_hi_tag | isNothing mb_deflt = highest_branch | otherwise = hi_tag n_tags = real_hi_tag - real_lo_tag + 1 -- INVARIANT: Provided hi_tag > lo_tag (which is true) -- lo_tag <= mid_tag < hi_tag -- lo_branches have tags < mid_tag -- hi_branches have tags >= mid_tag (mid_tag,_) = branches !! (n_branches `div` 2) -- 2 branches => n_branches `div` 2 = 1 -- => branches !! 1 give the *second* tag -- There are always at least 2 branches here (lo_branches, hi_branches) = span is_lo branches is_lo (t,_) = t < mid_tag -------------- mkCmmLitSwitch :: CmmExpr -- Tag to switch on -> [(Literal, CmmAGraph)] -- Tagged branches -> CmmAGraph -- Default branch (always) -> CmmAGraph -- Emit the code -- Used for general literals, whose size might not be a word, -- where there is always a default case, and where we don't know -- the range of values for certain. For simplicity we always generate a tree. -- -- ToDo: for integers we could do better here, perhaps by generalising -- mk_switch and using that. --SDM 15/09/2004 mkCmmLitSwitch _scrut [] deflt = deflt mkCmmLitSwitch scrut branches deflt = assignTemp' scrut $ \ scrut' -> withFreshLabel "switch join" $ \ join_lbl -> label_code join_lbl deflt $ \ deflt -> label_branches join_lbl branches $ \ branches -> mk_lit_switch scrut' deflt (sortLe le branches) <*> mkLabel join_lbl where le (t1,_) (t2,_) = t1 <= t2 mk_lit_switch :: CmmExpr -> BlockId -> [(Literal,BlockId)] -> CmmAGraph mk_lit_switch scrut deflt [(lit,blk)] = mkCbranch (CmmMachOp ne [scrut, CmmLit cmm_lit]) deflt blk where cmm_lit = mkSimpleLit lit cmm_ty = cmmLitType cmm_lit rep = typeWidth cmm_ty ne = if isFloatType cmm_ty then MO_F_Ne rep else MO_Ne rep mk_lit_switch scrut deflt_blk_id branches = mkCmmIfThenElse cond (mk_lit_switch scrut deflt_blk_id lo_branches) (mk_lit_switch scrut deflt_blk_id hi_branches) where n_branches = length branches (mid_lit,_) = branches !! (n_branches `div` 2) -- See notes above re mid_tag (lo_branches, hi_branches) = span is_lo branches is_lo (t,_) = t < mid_lit cond = CmmMachOp (mkLtOp mid_lit) [scrut, CmmLit (mkSimpleLit mid_lit)] -------------- label_default :: BlockId -> Maybe CmmAGraph -> (Maybe BlockId -> CmmAGraph) -> CmmAGraph label_default _ Nothing thing_inside = thing_inside Nothing label_default join_lbl (Just code) thing_inside = label_code join_lbl code $ \ lbl -> thing_inside (Just lbl) -------------- label_branches :: BlockId -> [(a,CmmAGraph)] -> ([(a,BlockId)] -> CmmAGraph) -> CmmAGraph label_branches _join_lbl [] thing_inside = thing_inside [] label_branches join_lbl ((tag,code):branches) thing_inside = label_code join_lbl code $ \ lbl -> label_branches join_lbl branches $ \ branches' -> thing_inside ((tag,lbl):branches') -------------- label_code :: BlockId -> CmmAGraph -> (BlockId -> CmmAGraph) -> CmmAGraph -- (label_code J code fun) -- generates -- [L: code; goto J] fun L label_code join_lbl code thing_inside = withFreshLabel "switch" $ \lbl -> outOfLine (mkLabel lbl <*> code <*> mkBranch join_lbl) <*> thing_inside lbl -------------- assignTemp' :: CmmExpr -> (CmmExpr -> CmmAGraph) -> CmmAGraph assignTemp' e thing_inside | isTrivialCmmExpr e = thing_inside e | otherwise = withTemp (cmmExprType e) $ \ lreg -> let reg = CmmLocal lreg in mkAssign reg e <*> thing_inside (CmmReg reg) withTemp :: CmmType -> (LocalReg -> CmmAGraph) -> CmmAGraph withTemp rep thing_inside = withUnique $ \uniq -> thing_inside (LocalReg uniq rep) ------------------------------------------------------------------------- -- -- Static Reference Tables -- ------------------------------------------------------------------------- -- There is just one SRT for each top level binding; all the nested -- bindings use sub-sections of this SRT. The label is passed down to -- the nested bindings via the monad. getSRTInfo :: SRT -> FCode C_SRT getSRTInfo (SRTEntries {}) = panic "getSRTInfo" getSRTInfo (SRT off len bmp) | len > hALF_WORD_SIZE_IN_BITS || bmp == [fromIntegral srt_escape] = do { id <- newUnique -- ; top_srt <- getSRTLabel ; let srt_desc_lbl = mkLargeSRTLabel id -- JD: We're not constructing and emitting SRTs in the back end, -- which renders this code wrong (it now names a now-non-existent label). -- ; emitRODataLits srt_desc_lbl -- ( cmmLabelOffW top_srt off -- : mkWordCLit (fromIntegral len) -- : map mkWordCLit bmp) ; return (C_SRT srt_desc_lbl 0 srt_escape) } | otherwise = do { top_srt <- getSRTLabel ; return (C_SRT top_srt off (fromIntegral (head bmp))) } -- The fromIntegral converts to StgHalfWord getSRTInfo NoSRT = -- TODO: Should we panic in this case? -- Someone obviously thinks there should be an SRT return NoC_SRT srt_escape :: StgHalfWord srt_escape = -1