----------------------------------------------------------------------------- -- -- Code generator utilities; mostly monadic -- -- (c) The University of Glasgow 2004-2006 -- ----------------------------------------------------------------------------- {-# OPTIONS_GHC -w #-} -- The above warning supression flag is a temporary kludge. -- While working on this module you are encouraged to remove it and fix -- any warnings in the module. See -- http://hackage.haskell.org/trac/ghc/wiki/WorkingConventions#Warnings -- for details module CgUtils ( addIdReps, cgLit, emitDataLits, mkDataLits, emitRODataLits, mkRODataLits, emitIf, emitIfThenElse, emitRtsCall, emitRtsCallWithVols, emitRtsCallWithResult, assignNonPtrTemp, newNonPtrTemp, assignPtrTemp, newPtrTemp, emitSimultaneously, emitSwitch, emitLitSwitch, tagToClosure, callerSaveVolatileRegs, get_GlobalReg_addr, cmmAndWord, cmmOrWord, cmmNegate, cmmEqWord, cmmNeWord, cmmUGtWord, cmmOffsetExprW, cmmOffsetExprB, cmmRegOffW, cmmRegOffB, cmmLabelOffW, cmmLabelOffB, cmmOffsetW, cmmOffsetB, cmmOffsetLitW, cmmOffsetLitB, cmmLoadIndexW, cmmConstrTag, cmmConstrTag1, tagForCon, tagCons, isSmallFamily, cmmUntag, cmmIsTagged, cmmGetTag, addToMem, addToMemE, mkWordCLit, mkStringCLit, mkByteStringCLit, packHalfWordsCLit, blankWord, getSRTInfo ) where #include "HsVersions.h" #include "MachRegs.h" import CgMonad import TyCon import DataCon import Id import Constants import SMRep import PprCmm ( {- instances -} ) import Cmm import CLabel import CmmUtils import MachOp import ForeignCall import ClosureInfo import StgSyn (SRT(..)) import Literal import Digraph import ListSetOps import Util import DynFlags import FastString import PackageConfig #ifdef DEBUG import Outputable #endif import Data.Char import Data.Bits import Data.Word import Data.Maybe ------------------------------------------------------------------------- -- -- Random small functions -- ------------------------------------------------------------------------- addIdReps :: [Id] -> [(CgRep, Id)] addIdReps ids = [(idCgRep id, id) | id <- ids] ------------------------------------------------------------------------- -- -- 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)) wordRep mkSimpleLit MachNullAddr = zeroCLit mkSimpleLit (MachInt i) = CmmInt i wordRep mkSimpleLit (MachInt64 i) = CmmInt i I64 mkSimpleLit (MachWord i) = CmmInt i wordRep mkSimpleLit (MachWord64 i) = CmmInt i I64 mkSimpleLit (MachFloat r) = CmmFloat r F32 mkSimpleLit (MachDouble r) = CmmFloat r F64 mkSimpleLit (MachLabel fs ms) = CmmLabel (mkForeignLabel fs ms is_dyn) where is_dyn = False -- ToDo: fix me mkLtOp :: Literal -> MachOp -- On signed literals we must do a signed comparison mkLtOp (MachInt _) = MO_S_Lt wordRep mkLtOp (MachFloat _) = MO_S_Lt F32 mkLtOp (MachDouble _) = MO_S_Lt F64 mkLtOp lit = MO_U_Lt (cmmLitRep (mkSimpleLit lit)) --------------------------------------------------- -- -- 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 wordRep 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 -> CmmExpr cmmLoadIndexW base off = CmmLoad (cmmOffsetW base off) wordRep ----------------------- 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 (cmmExprRep e)) [e] blankWord :: CmmStatic blankWord = CmmUninitialised wORD_SIZE -- Tagging -- -- Tag bits mask --cmmTagBits = CmmLit (mkIntCLit tAG_BITS) 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 e@(CmmLit (CmmLabel _)) = e -- Default case cmmUntag e = (e `cmmAndWord` cmmPointerMask) cmmGetTag e = (e `cmmAndWord` cmmTagMask) -- Test if a closure pointer is untagged cmmIsTagged e = (e `cmmAndWord` cmmTagMask) `cmmNeWord` CmmLit zeroCLit cmmConstrTag e = (e `cmmAndWord` cmmTagMask) `cmmSubWord` (CmmLit (mkIntCLit 1)) -- Get constructor tag, but one based. cmmConstrTag1 e = e `cmmAndWord` cmmTagMask {- The family size of a data type (the number of constructors) can be either: * small, if the family size < 2**tag_bits * big, otherwise. Small families can have the constructor tag in the tag bits. Big families only use the tag value 1 to represent evaluatedness. -} isSmallFamily fam_size = fam_size <= mAX_PTR_TAG tagForCon con = tag where con_tag = dataConTagZ con fam_size = tyConFamilySize (dataConTyCon con) tag | isSmallFamily fam_size = con_tag + 1 | otherwise = 1 --Tag an expression, to do: refactor, this appears in some other module. tagCons con expr = cmmOffsetB expr (tagForCon con) -- Copied from CgInfoTbls.hs -- We keep the *zero-indexed* tag in the srt_len field of the info -- table of a data constructor. dataConTagZ :: DataCon -> ConTagZ dataConTagZ con = dataConTag con - fIRST_TAG ----------------------- -- Making literals mkWordCLit :: StgWord -> CmmLit mkWordCLit wd = CmmInt (fromIntegral wd) wordRep 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 -- -------------------------------------------------------------------------- addToMem :: MachRep -- rep of the counter -> CmmExpr -- Address -> Int -- What to add (a word) -> CmmStmt addToMem rep ptr n = addToMemE rep ptr (CmmLit (CmmInt (toInteger n) rep)) addToMemE :: MachRep -- rep of the counter -> CmmExpr -- Address -> CmmExpr -- What to add (a word-typed expression) -> CmmStmt addToMemE rep ptr n = CmmStore ptr (CmmMachOp (MO_Add rep) [CmmLoad ptr rep, n]) ------------------------------------------------------------------------- -- -- 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) wordRep where closure_tbl = CmmLit (CmmLabel lbl) lbl = mkClosureTableLabel (tyConName tycon) ------------------------------------------------------------------------- -- -- Conditionals and rts calls -- ------------------------------------------------------------------------- emitIf :: CmmExpr -- Boolean -> Code -- Then part -> Code -- Emit (if e then x) -- ToDo: reverse the condition to avoid the extra branch instruction if possible -- (some conditionals aren't reversible. eg. floating point comparisons cannot -- be inverted because there exist some values for which both comparisons -- return False, such as NaN.) emitIf cond then_part = do { then_id <- newLabelC ; join_id <- newLabelC ; stmtC (CmmCondBranch cond then_id) ; stmtC (CmmBranch join_id) ; labelC then_id ; then_part ; labelC join_id } emitIfThenElse :: CmmExpr -- Boolean -> Code -- Then part -> Code -- Else part -> Code -- Emit (if e then x else y) emitIfThenElse cond then_part else_part = do { then_id <- newLabelC ; else_id <- newLabelC ; join_id <- newLabelC ; stmtC (CmmCondBranch cond then_id) ; else_part ; stmtC (CmmBranch join_id) ; labelC then_id ; then_part ; labelC join_id } emitRtsCall :: LitString -> [(CmmExpr,MachHint)] -> Bool -> Code emitRtsCall fun args safe = emitRtsCall' [] fun args Nothing safe -- The 'Nothing' says "save all global registers" emitRtsCallWithVols :: LitString -> [(CmmExpr,MachHint)] -> [GlobalReg] -> Bool -> Code emitRtsCallWithVols fun args vols safe = emitRtsCall' [] fun args (Just vols) safe emitRtsCallWithResult :: LocalReg -> MachHint -> LitString -> [(CmmExpr,MachHint)] -> Bool -> Code emitRtsCallWithResult res hint fun args safe = emitRtsCall' [(res,hint)] fun args Nothing safe -- Make a call to an RTS C procedure emitRtsCall' :: CmmHintFormals -> LitString -> [(CmmExpr,MachHint)] -> Maybe [GlobalReg] -> Bool -- True <=> CmmSafe call -> Code emitRtsCall' res fun args vols safe = do safety <- if safe then getSRTInfo >>= (return . CmmSafe) else return CmmUnsafe stmtsC caller_save stmtC (CmmCall target res args safety CmmMayReturn) stmtsC caller_load where (caller_save, caller_load) = callerSaveVolatileRegs vols target = CmmCallee fun_expr CCallConv 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 :: Maybe [GlobalReg] -> ([CmmStmt], [CmmStmt]) callerSaveVolatileRegs vols = (caller_save, caller_load) where caller_save = foldr ($!) [] (map callerSaveGlobalReg regs_to_save) caller_load = foldr ($!) [] (map callerRestoreGlobalReg regs_to_save) system_regs = [Sp,SpLim,Hp,HpLim,CurrentTSO,CurrentNursery, {-SparkHd,SparkTl,SparkBase,SparkLim,-}BaseReg ] regs_to_save = system_regs ++ vol_list vol_list = case vols of Nothing -> all_of_em; Just regs -> regs all_of_em = [ VanillaReg n | n <- [0..mAX_Vanilla_REG] ] ++ [ FloatReg n | n <- [0..mAX_Float_REG] ] ++ [ DoubleReg n | n <- [0..mAX_Double_REG] ] ++ [ LongReg n | n <- [0..mAX_Long_REG] ] callerSaveGlobalReg reg next | callerSaves reg = CmmStore (get_GlobalReg_addr reg) (CmmReg (CmmGlobal reg)) : next | otherwise = next callerRestoreGlobalReg reg next | callerSaves reg = CmmAssign (CmmGlobal reg) (CmmLoad (get_GlobalReg_addr reg) (globalRegRep reg)) : next | otherwise = next -- ----------------------------------------------------------------------------- -- 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 (globalRegRep 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 n = CmmLit (CmmLabelOff mkMainCapabilityLabel (oFFSET_Capability_r + n)) get_Regtable_addr_from_offset :: MachRep -> 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_R1 callerSaves (VanillaReg 1) = True #endif #ifdef CALLER_SAVES_R2 callerSaves (VanillaReg 2) = True #endif #ifdef CALLER_SAVES_R3 callerSaves (VanillaReg 3) = True #endif #ifdef CALLER_SAVES_R4 callerSaves (VanillaReg 4) = True #endif #ifdef CALLER_SAVES_R5 callerSaves (VanillaReg 5) = True #endif #ifdef CALLER_SAVES_R6 callerSaves (VanillaReg 6) = True #endif #ifdef CALLER_SAVES_R7 callerSaves (VanillaReg 7) = True #endif #ifdef CALLER_SAVES_R8 callerSaves (VanillaReg 8) = True #endif #ifdef CALLER_SAVES_F1 callerSaves (FloatReg 1) = True #endif #ifdef CALLER_SAVES_F2 callerSaves (FloatReg 2) = True #endif #ifdef CALLER_SAVES_F3 callerSaves (FloatReg 3) = True #endif #ifdef CALLER_SAVES_F4 callerSaves (FloatReg 4) = True #endif #ifdef CALLER_SAVES_D1 callerSaves (DoubleReg 1) = True #endif #ifdef CALLER_SAVES_D2 callerSaves (DoubleReg 2) = True #endif #ifdef CALLER_SAVES_L1 callerSaves (LongReg 1) = 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 (VanillaReg 1) = oFFSET_StgRegTable_rR1 baseRegOffset (VanillaReg 2) = oFFSET_StgRegTable_rR2 baseRegOffset (VanillaReg 3) = oFFSET_StgRegTable_rR3 baseRegOffset (VanillaReg 4) = oFFSET_StgRegTable_rR4 baseRegOffset (VanillaReg 5) = oFFSET_StgRegTable_rR5 baseRegOffset (VanillaReg 6) = oFFSET_StgRegTable_rR6 baseRegOffset (VanillaReg 7) = oFFSET_StgRegTable_rR7 baseRegOffset (VanillaReg 8) = oFFSET_StgRegTable_rR8 baseRegOffset (VanillaReg 9) = oFFSET_StgRegTable_rR9 baseRegOffset (VanillaReg 10) = oFFSET_StgRegTable_rR10 baseRegOffset (FloatReg 1) = oFFSET_StgRegTable_rF1 baseRegOffset (FloatReg 2) = oFFSET_StgRegTable_rF2 baseRegOffset (FloatReg 3) = oFFSET_StgRegTable_rF3 baseRegOffset (FloatReg 4) = oFFSET_StgRegTable_rF4 baseRegOffset (DoubleReg 1) = oFFSET_StgRegTable_rD1 baseRegOffset (DoubleReg 2) = oFFSET_StgRegTable_rD2 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 #ifdef DEBUG baseRegOffset BaseReg = panic "baseRegOffset:BaseReg" baseRegOffset _ = panic "baseRegOffset:other" #endif ------------------------------------------------------------------------- -- -- Strings generate a top-level data block -- ------------------------------------------------------------------------- emitDataLits :: CLabel -> [CmmLit] -> Code -- 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] -> Code -- 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 -- ------------------------------------------------------------------------- assignNonPtrTemp :: CmmExpr -> FCode CmmExpr -- For a non-trivial expression, e, create a local -- variable and assign the expression to it assignNonPtrTemp e | isTrivialCmmExpr e = return e | otherwise = do { reg <- newNonPtrTemp (cmmExprRep e) ; stmtC (CmmAssign (CmmLocal reg) e) ; return (CmmReg (CmmLocal reg)) } assignPtrTemp :: CmmExpr -> FCode CmmExpr -- For a non-trivial expression, e, create a local -- variable and assign the expression to it assignPtrTemp e | isTrivialCmmExpr e = return e | otherwise = do { reg <- newPtrTemp (cmmExprRep e) ; stmtC (CmmAssign (CmmLocal reg) e) ; return (CmmReg (CmmLocal reg)) } newNonPtrTemp :: MachRep -> FCode LocalReg newNonPtrTemp rep = do { uniq <- newUnique; return (LocalReg uniq rep KindNonPtr) } newPtrTemp :: MachRep -> FCode LocalReg newPtrTemp rep = do { uniq <- newUnique; return (LocalReg uniq rep KindPtr) } ------------------------------------------------------------------------- -- -- Building case analysis -- ------------------------------------------------------------------------- emitSwitch :: CmmExpr -- Tag to switch on -> [(ConTagZ, CgStmts)] -- Tagged branches -> Maybe CgStmts -- Default branch (if any) -> ConTagZ -> ConTagZ -- Min and Max possible values; behaviour -- outside this range is undefined -> Code -- ONLY A DEFAULT BRANCH: no case analysis to do emitSwitch tag_expr [] (Just stmts) _ _ = emitCgStmts stmts -- Right, off we go emitSwitch tag_expr branches mb_deflt lo_tag hi_tag = -- Just sort the branches before calling mk_sritch do { mb_deflt_id <- case mb_deflt of Nothing -> return Nothing Just stmts -> do id <- forkCgStmts stmts; return (Just id) ; dflags <- getDynFlags ; let via_C | HscC <- hscTarget dflags = True | otherwise = False ; stmts <- mk_switch tag_expr (sortLe le branches) mb_deflt_id lo_tag hi_tag via_C ; emitCgStmts stmts } where (t1,_) `le` (t2,_) = t1 <= t2 mk_switch :: CmmExpr -> [(ConTagZ, CgStmts)] -> Maybe BlockId -> ConTagZ -> ConTagZ -> Bool -> FCode CgStmts -- SINGLETON TAG RANGE: no case analysis to do mk_switch tag_expr [(tag,stmts)] _ lo_tag hi_tag via_C | lo_tag == hi_tag = ASSERT( tag == lo_tag ) return stmts -- SINGLETON BRANCH, NO DEFUALT: no case analysis to do mk_switch tag_expr [(tag,stmts)] Nothing lo_tag hi_tag via_C = return stmts -- 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,stmts)] (Just deflt) lo_tag hi_tag via_C = return (CmmCondBranch cond deflt `consCgStmt` stmts) 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 = do { branch_ids <- mapM forkCgStmts (map snd branches) ; let tagged_blk_ids = zip (map fst branches) (map Just branch_ids) find_branch :: ConTagZ -> Maybe BlockId find_branch i = assocDefault mb_deflt tagged_blk_ids i -- 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 = [ find_branch i | i <- [real_lo_tag..real_hi_tag]] switch_stmt = CmmSwitch (cmmOffset tag_expr (- real_lo_tag)) arms ; ASSERT(not (all isNothing arms)) return (oneCgStmt switch_stmt) } -- 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 = do { (assign_tag, tag_expr') <- assignNonPtrTemp' tag_expr ; let cond = cmmULtWord tag_expr' (CmmLit (mkIntCLit lowest_branch)) branch = CmmCondBranch cond deflt ; stmts <- mk_switch tag_expr' branches mb_deflt lowest_branch hi_tag via_C ; return (assign_tag `consCgStmt` (branch `consCgStmt` stmts)) } | Just deflt <- mb_deflt, (hi_tag - highest_branch) >= n_branches = do { (assign_tag, tag_expr') <- assignNonPtrTemp' tag_expr ; let cond = cmmUGtWord tag_expr' (CmmLit (mkIntCLit highest_branch)) branch = CmmCondBranch cond deflt ; stmts <- mk_switch tag_expr' branches mb_deflt lo_tag highest_branch via_C ; return (assign_tag `consCgStmt` (branch `consCgStmt` stmts)) } | otherwise -- Use an if-tree = do { (assign_tag, tag_expr') <- assignNonPtrTemp' tag_expr -- To avoid duplication ; lo_stmts <- mk_switch tag_expr' lo_branches mb_deflt lo_tag (mid_tag-1) via_C ; hi_stmts <- mk_switch tag_expr' hi_branches mb_deflt mid_tag hi_tag via_C ; hi_id <- forkCgStmts hi_stmts ; let cond = cmmUGeWord tag_expr' (CmmLit (mkIntCLit mid_tag)) branch_stmt = CmmCondBranch cond hi_id ; return (assign_tag `consCgStmt` (branch_stmt `consCgStmt` lo_stmts)) } -- 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 assignNonPtrTemp' e | isTrivialCmmExpr e = return (CmmNop, e) | otherwise = do { reg <- newNonPtrTemp (cmmExprRep e) ; return (CmmAssign (CmmLocal reg) e, CmmReg (CmmLocal reg)) } emitLitSwitch :: CmmExpr -- Tag to switch on -> [(Literal, CgStmts)] -- Tagged branches -> CgStmts -- Default branch (always) -> Code -- 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 emitLitSwitch scrut [] deflt = emitCgStmts deflt emitLitSwitch scrut branches deflt_blk = do { scrut' <- assignNonPtrTemp scrut ; deflt_blk_id <- forkCgStmts deflt_blk ; blk <- mk_lit_switch scrut' deflt_blk_id (sortLe le branches) ; emitCgStmts blk } where le (t1,_) (t2,_) = t1 <= t2 mk_lit_switch :: CmmExpr -> BlockId -> [(Literal,CgStmts)] -> FCode CgStmts mk_lit_switch scrut deflt_blk_id [(lit,blk)] = return (consCgStmt if_stmt blk) where cmm_lit = mkSimpleLit lit rep = cmmLitRep cmm_lit cond = CmmMachOp (MO_Ne rep) [scrut, CmmLit cmm_lit] if_stmt = CmmCondBranch cond deflt_blk_id mk_lit_switch scrut deflt_blk_id branches = do { hi_blk <- mk_lit_switch scrut deflt_blk_id hi_branches ; lo_blk <- mk_lit_switch scrut deflt_blk_id lo_branches ; lo_blk_id <- forkCgStmts lo_blk ; let if_stmt = CmmCondBranch cond lo_blk_id ; return (if_stmt `consCgStmt` hi_blk) } 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)] ------------------------------------------------------------------------- -- -- Simultaneous assignment -- ------------------------------------------------------------------------- emitSimultaneously :: CmmStmts -> Code -- Emit code to perform the assignments in the -- input simultaneously, using temporary variables when necessary. -- -- The Stmts must be: -- CmmNop, CmmComment, CmmAssign, CmmStore -- and nothing else -- 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 type CVertex = (Int, CmmStmt) -- Give each vertex a unique number, -- for fast comparison emitSimultaneously stmts = codeOnly $ case filterOut isNopStmt (stmtList stmts) of -- Remove no-ops [] -> nopC [stmt] -> stmtC stmt -- It's often just one stmt stmt_list -> doSimultaneously1 (zip [(1::Int)..] stmt_list) doSimultaneously1 :: [CVertex] -> Code doSimultaneously1 vertices = let edges = [ (vertex, key1, edges_from stmt1) | vertex@(key1, stmt1) <- vertices ] edges_from stmt1 = [ key2 | (key2, stmt2) <- vertices, stmt1 `mustFollow` stmt2 ] components = stronglyConnComp edges -- do_components deal with one strongly-connected component -- Not cyclic, or singleton? Just do it do_component (AcyclicSCC (n,stmt)) = stmtC stmt do_component (CyclicSCC [(n,stmt)]) = stmtC stmt -- Cyclic? Then go via temporaries. Pick one to -- break the loop and try again with the rest. do_component (CyclicSCC ((n,first_stmt) : rest)) = do { from_temp <- go_via_temp first_stmt ; doSimultaneously1 rest ; stmtC from_temp } go_via_temp (CmmAssign dest src) = do { tmp <- newNonPtrTemp (cmmRegRep dest) -- TODO FIXME NOW if the pair of assignments move across a call this will be wrong ; stmtC (CmmAssign (CmmLocal tmp) src) ; return (CmmAssign dest (CmmReg (CmmLocal tmp))) } go_via_temp (CmmStore dest src) = do { tmp <- newNonPtrTemp (cmmExprRep src) -- TODO FIXME NOW if the pair of assignemnts move across a call this will be wrong ; stmtC (CmmAssign (CmmLocal tmp) src) ; return (CmmStore dest (CmmReg (CmmLocal tmp))) } in mapCs do_component components mustFollow :: CmmStmt -> CmmStmt -> Bool CmmAssign reg _ `mustFollow` stmt = anySrc (reg `regUsedIn`) stmt CmmStore loc e `mustFollow` stmt = anySrc (locUsedIn loc (cmmExprRep e)) stmt CmmNop `mustFollow` stmt = False CmmComment _ `mustFollow` stmt = False anySrc :: (CmmExpr -> Bool) -> CmmStmt -> Bool -- True if the fn is true of any input of the stmt anySrc p (CmmAssign _ e) = p e anySrc p (CmmStore e1 e2) = p e1 || p e2 -- Might be used in either side anySrc p (CmmComment _) = False anySrc p CmmNop = False anySrc p other = True -- Conservative regUsedIn :: CmmReg -> CmmExpr -> Bool reg `regUsedIn` CmmLit _ = False reg `regUsedIn` CmmLoad e _ = reg `regUsedIn` e reg `regUsedIn` CmmReg reg' = reg == reg' reg `regUsedIn` CmmRegOff reg' _ = reg == reg' reg `regUsedIn` CmmMachOp _ es = any (reg `regUsedIn`) es locUsedIn :: CmmExpr -> MachRep -> CmmExpr -> Bool -- (locUsedIn a r e) checks whether writing to r[a] could affect the value of -- 'e'. Returns True if it's not sure. locUsedIn loc rep (CmmLit _) = False locUsedIn loc rep (CmmLoad e ld_rep) = possiblySameLoc loc rep e ld_rep locUsedIn loc rep (CmmReg reg') = False locUsedIn loc rep (CmmRegOff reg' _) = False locUsedIn loc rep (CmmMachOp _ es) = any (locUsedIn loc rep) es possiblySameLoc :: CmmExpr -> MachRep -> CmmExpr -> MachRep -> Bool -- Assumes that distinct registers (eg Hp, Sp) do not -- point to the same location, nor any offset thereof. possiblySameLoc (CmmReg r1) rep1 (CmmReg r2) rep2 = r1==r2 possiblySameLoc (CmmReg r1) rep1 (CmmRegOff r2 0) rep2 = r1==r2 possiblySameLoc (CmmRegOff r1 0) rep1 (CmmReg r2) rep2 = r1==r2 possiblySameLoc (CmmRegOff r1 start1) rep1 (CmmRegOff r2 start2) rep2 = r1==r2 && end1 > start2 && end2 > start1 where end1 = start1 + machRepByteWidth rep1 end2 = start2 + machRepByteWidth rep2 possiblySameLoc l1 rep1 (CmmLit _) rep2 = False possiblySameLoc l1 rep1 l2 rep2 = True -- Conservative ------------------------------------------------------------------------- -- -- 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 :: FCode C_SRT getSRTInfo = do srt_lbl <- getSRTLabel srt <- getSRT case srt of -- TODO: Should we panic in this case? -- Someone obviously thinks there should be an SRT NoSRT -> return NoC_SRT SRT off len bmp | len > hALF_WORD_SIZE_IN_BITS || bmp == [fromIntegral srt_escape] -> do id <- newUnique let srt_desc_lbl = mkLargeSRTLabel id emitRODataLits srt_desc_lbl ( cmmLabelOffW srt_lbl off : mkWordCLit (fromIntegral len) : map mkWordCLit bmp) return (C_SRT srt_desc_lbl 0 srt_escape) SRT off len bmp | otherwise -> return (C_SRT srt_lbl off (fromIntegral (head bmp))) -- The fromIntegral converts to StgHalfWord srt_escape = (-1) :: StgHalfWord