{-# LANGUAGE CPP #-}
{-# OPTIONS_GHC -fno-warn-unused-matches #-}
{-# OPTIONS_GHC -fno-warn-unused-binds #-}
{-# OPTIONS_GHC -fno-warn-missing-signatures #-}
{-# OPTIONS_GHC -fno-warn-overlapping-patterns #-}
{-# OPTIONS_GHC -fno-warn-incomplete-patterns #-}
{-# OPTIONS_GHC -fno-warn-name-shadowing #-}
-- The above warning suppression flags are a temporary kludge.
-- While working on this module you are encouraged to remove it and fix
-- any warnings in the module. See
--     https://gitlab.haskell.org/ghc/ghc/wikis/commentary/coding-style#warnings
-- for details
module Main(main) where

-- Note [Genapply target as host for RTS macros]
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- We improperly include *HOST* macros for our target...
#include "../../rts/include/ghcconfig.h"

-- ...so that this header defines the right stuff.  It is the RTS's host, but
-- our target, as we are generating code that uses that RTS.
#include "../../rts/include/stg/MachRegsForHost.h"

#include "../../rts/include/rts/Constants.h"

-- Needed for TAG_BITS
#include "../../rts/include/MachDeps.h"

import Prelude hiding ((<>))

import Text.PrettyPrint
import Data.Word
import Data.Bits
import Data.List        ( intersperse, nub, sort )
import System.Exit
import System.Environment
import System.IO
import Control.Arrow ((***))

-- -----------------------------------------------------------------------------
-- Argument kinds (roughly equivalent to PrimRep)

data ArgRep
  = N   -- non-ptr
  | P   -- ptr
  | V   -- void
  | F   -- float
  | D   -- double
  | L   -- long (64-bit)
  | V16 -- 16-byte (128-bit) vectors
  | V32 -- 32-byte (256-bit) vectors
  | V64 -- 64-byte (512-bit) vectors

-- size of a value in *words*
argSize :: ArgRep -> Int
argSize N   = 1
argSize P   = 1
argSize V   = 0
argSize F   = 1
argSize D   = (SIZEOF_DOUBLE `quot` SIZEOF_VOID_P :: Int)
argSize L   = (8 `quot` SIZEOF_VOID_P :: Int)
argSize V16 = (16 `quot` SIZEOF_VOID_P :: Int)
argSize V32 = (32 `quot` SIZEOF_VOID_P :: Int)
argSize V64 = (64 `quot` SIZEOF_VOID_P :: Int)

showArg :: ArgRep -> String
showArg N   = "n"
showArg P   = "p"
showArg V   = "v"
showArg F   = "f"
showArg D   = "d"
showArg L   = "l"
showArg V16 = "v16"
showArg V32 = "v32"
showArg V64 = "v64"

-- is a value a pointer?
isPtr :: ArgRep -> Bool
isPtr P = True
isPtr _ = False

-- -----------------------------------------------------------------------------
-- Registers

data RegStatus = Registerised | Unregisterised

type Reg = String

availableRegs :: RegStatus -> ([Reg],[Reg],[Reg],[Reg])
availableRegs Unregisterised = ([],[],[],[])
availableRegs Registerised =
  ( vanillaRegs MAX_REAL_VANILLA_REG,
    floatRegs   MAX_REAL_FLOAT_REG,
    doubleRegs  MAX_REAL_DOUBLE_REG,
    longRegs    MAX_REAL_LONG_REG
  )

vanillaRegs, floatRegs, doubleRegs, longRegs :: Int -> [Reg]
vanillaRegs n = [ "R" ++ show m | m <- [2..n] ]  -- never use R1
floatRegs   n = [ "F" ++ show m | m <- [1..n] ]
doubleRegs  n = [ "D" ++ show m | m <- [1..n] ]
longRegs    n = [ "L" ++ show m | m <- [1..n] ]

-- -----------------------------------------------------------------------------
-- Loading/saving register arguments to the stack

loadRegArgs :: RegStatus -> Int -> [ArgRep] -> (Doc,Int)
loadRegArgs regstatus sp args
 = (loadRegOffs reg_locs, sp')
 where (reg_locs, _, sp') = assignRegs regstatus sp args

loadRegOffs :: [(Reg,Int)] -> Doc
loadRegOffs = vcat . map (uncurry assign_stk_to_reg)

saveRegOffs :: [(Reg,Int)] -> Doc
saveRegOffs = vcat . map (uncurry assign_reg_to_stk)

assignRegs
        :: RegStatus            -- are we registerised?
        -> Int                  -- Sp of first arg
        -> [ArgRep]             -- args
        -> ([(Reg,Int)],        -- regs and offsets to load
            [ArgRep],           -- left-over args
            Int)                -- Sp of left-over args
assignRegs regstatus sp args = assign sp args (availableRegs regstatus) []

assign sp [] regs doc = (doc, [], sp)
assign sp (V : args) regs doc = assign sp args regs doc
assign sp (arg : args) regs doc
 = case findAvailableReg arg regs of
    Just (reg, regs') -> assign (sp + argSize arg)  args regs'
                            ((reg, sp) : doc)
    Nothing -> (doc, (arg:args), sp)

findAvailableReg N (vreg:vregs, fregs, dregs, lregs) =
  Just (vreg, (vregs,fregs,dregs,lregs))
findAvailableReg P (vreg:vregs, fregs, dregs, lregs) =
  Just (vreg, (vregs,fregs,dregs,lregs))
findAvailableReg F (vregs, freg:fregs, dregs, lregs) =
  Just (freg, (vregs,fregs,dregs,lregs))
findAvailableReg D (vregs, fregs, dreg:dregs, lregs) =
  Just (dreg, (vregs,fregs,dregs,lregs))
findAvailableReg L (vregs, fregs, dregs, lreg:lregs) =
  Just (lreg, (vregs,fregs,dregs,lregs))
findAvailableReg _ _ = Nothing

assign_reg_to_stk reg sp
   = loadSpWordOff (regRep reg) sp <> text " = " <> text reg <> semi

assign_stk_to_reg reg sp
   = text reg <> text " = " <> loadSpWordOff (regRep reg) sp <> semi

regRep ('F':_) = "F_"
regRep ('D':_) = "D_"
regRep ('L':_) = "L_"
regRep _       = "W_"

loadSpWordOff :: String -> Int -> Doc
loadSpWordOff rep off = text rep <> text "[Sp+WDS(" <> int off <> text ")]"

-- Make a jump
mkJump :: RegStatus -- Registerised status
       -> Doc       -- Jump target
       -> [Reg]     -- Registers that are definitely live
       -> [ArgRep]  -- Jump arguments
       -> Doc
mkJump regstatus jump live args =
    text "jump" <+> jump <+> brackets (hcat (punctuate comma liveRegs))
  where
    liveRegs = mkJumpLiveRegs regstatus live args

-- Make a jump, saving CCCS and restoring it on return
mkJumpSaveCCCS :: RegStatus -- Registerised status
               -> Doc       -- Jump target
               -> [Reg]     -- Registers that are definitely live
               -> [ArgRep]  -- Jump arguments
               -> Doc
mkJumpSaveCCCS regstatus jump live args =
    text "jump_SAVE_CCCS" <> parens (hcat (punctuate comma (jump : liveRegs)))
  where
    liveRegs = mkJumpLiveRegs regstatus live args

-- Calculate live registers for a jump
mkJumpLiveRegs :: RegStatus -- Registerised status
               -> [Reg]     -- Registers that are definitely live
               -> [ArgRep]  -- Jump arguments
               -> [Doc]
mkJumpLiveRegs regstatus live args =
    map text regs
  where
    (reg_locs, _, _) = assignRegs regstatus 0 args
    regs             = (nub . sort) (live ++ map fst reg_locs)

-- make a ptr/non-ptr bitmap from a list of argument types
mkBitmap :: [ArgRep] -> Word32
mkBitmap args = foldr f 0 args
 where f arg bm | isPtr arg = bm `shiftL` 1
                | otherwise = (bm `shiftL` size) .|. ((1 `shiftL` size) - 1)
                where size = argSize arg

-- -----------------------------------------------------------------------------
-- Generating the application functions

-- A SUBTLE POINT about stg_ap functions (can't think of a better
-- place to put this comment --SDM):
--
-- The entry convention to an stg_ap_ function is as follows: all the
-- arguments are on the stack (we might revisit this at some point,
-- but it doesn't make any difference on x86), and THERE IS AN EXTRA
-- EMPTY STACK SLOT at the top of the stack.
--
-- Why?  Because in several cases, stg_ap_* will need an extra stack
-- slot, eg. to push a return address in the THUNK case, and this is a
-- way of pushing the stack check up into the caller which is probably
-- doing one anyway.  Allocating the extra stack slot in the caller is
-- also probably free, because it will be adjusting Sp after pushing
-- the args anyway (this might not be true of register-rich machines
-- when we start passing args to stg_ap_* in regs).

mkApplyName args
  = text "stg_ap_" <> text (concatMap showArg args)

mkApplyRetName args
  = mkApplyName args <> text "_ret"

mkApplyFastName args
  = mkApplyName args <> text "_fast"

mkApplyInfoName args
  = mkApplyName args <> text "_info"

mb_tag_node arity | Just tag <- tagForArity arity = mkTagStmt tag <> semi
                  | otherwise = empty

mkTagStmt tag = text ("R1 = R1 + "++ show tag)

type StackUsage = (Int, Int)  -- PROFILING, normal

maxStack :: [StackUsage] -> StackUsage
maxStack = (maximum *** maximum) . unzip

stackCheck
   :: RegStatus  -- Registerised status
   -> [ArgRep]
   -> Bool       -- args in regs?
   -> Doc        -- fun_info_label
   -> StackUsage
   -> Doc
stackCheck regstatus args args_in_regs fun_info_label (prof_sp, norm_sp) =
  let
     (reg_locs, leftovers, sp_offset) = assignRegs regstatus 1 args

     cmp_sp n
       | n > 0 =
          text "if (Sp - WDS(" <> int n <> text ") < SpLim) {" $$
          nest 4 (vcat [
            if args_in_regs
               then
                 text "Sp_adj" <> parens (int (-sp_offset)) <> semi $$
                 saveRegOffs reg_locs
               else
                 empty,
            text "Sp(0) = " <> fun_info_label <> char ';',
            mkJump regstatus (text "__stg_gc_enter_1") ["R1"] [] <> semi
            ]) $$
          char '}'
       | otherwise = empty
  in
  vcat [ text "#if defined(PROFILING)",
         cmp_sp prof_sp,
         text "#else",
         cmp_sp norm_sp,
         text "#endif"
       ]

genMkPAP :: RegStatus -- Register status
         -> String    -- Macro
         -> String    -- Jump target
         -> [Reg]     -- Registers that are definitely live
         -> String    -- Ticker
         -> String    -- Disamb
         -> Bool      -- Don't load argument registers before jump if True
         -> Bool      -- Arguments already in registers if True
         -> Bool      -- Is a PAP if True
         -> [ArgRep]  -- Arguments
         -> Int       -- Size of all arguments
         -> Doc       -- info label
         -> Bool      -- Is a function
         -> (Doc, StackUsage)
genMkPAP regstatus macro jump live ticker disamb
        no_load_regs    -- don't load argument regs before jumping
        args_in_regs    -- arguments are already in regs
        is_pap args all_args_size fun_info_label
        is_fun_case
  = (doc, stack_usage)

  where
    doc = vcat smaller_arity_doc $$ exact_arity_case $$ larger_arity_doc

    stack_usage = maxStack (larger_arity_stack : smaller_arity_stack)

    n_args = length args

        -- offset of arguments on the stack at slow apply calls.
    stk_args_slow_offset = 1

    stk_args_offset
        | args_in_regs = 0
        | otherwise    = stk_args_slow_offset

-- The SMALLER ARITY cases:
--      if (arity == 1) {
--          Sp[0] = Sp[1];
--          Sp[1] = (W_)&stg_ap_1_info;
--          JMP_(GET_ENTRY(R1.cl));
    (smaller_arity_doc, smaller_arity_stack)
       = unzip [ smaller_arity i | i <- [1..n_args-1] ]

    smaller_arity arity = (doc, stack_usage)
      where
        (save_regs, stack_usage)
          | overflow_regs = save_extra_regs
          | otherwise     = shuffle_extra_args

        doc =
           text "if (arity == " <> int arity <> text ") {" $$
           nest 4 (vcat [
           --  text "TICK_SLOW_CALL_" <> text ticker <> text "_TOO_MANY();",

                -- load up regs for the call, if necessary
             load_regs,

                -- If we have more args in registers than are required
                -- for the call, then we must save some on the stack,
                -- and set up the stack for the follow-up call.
                -- If the extra arguments are on the stack, then we must
                -- instead shuffle them down to make room for the info
                -- table for the follow-on call.
             save_regs,

                -- for a PAP, we have to arrange that the stack contains a
                -- return address in the event that stg_PAP_entry fails its
                -- heap check.  See stg_PAP_entry in Apply.cmm for details.
             if is_pap
                then text "R2 = " <> mkApplyInfoName this_call_args <> semi

                else empty,
            if is_fun_case then mb_tag_node arity else empty,
            if overflow_regs
                then mkJumpSaveCCCS
                       regstatus (text jump) live (take arity args) <> semi
                else mkJump regstatus (text jump) live (if no_load_regs then [] else args) <> semi
            ]) $$
           text "}"

           -- offsets in case we need to save regs:
        (reg_locs, _, _)
           = assignRegs regstatus stk_args_offset args

           -- register assignment for *this function call*
        (reg_locs', reg_call_leftovers, reg_call_sp_stk_args)
           = assignRegs regstatus stk_args_offset (take arity args)

        load_regs
           | no_load_regs || args_in_regs = empty
           | otherwise                    = loadRegOffs reg_locs'

        (this_call_args, rest_args) = splitAt arity args

           -- the offset of the stack args from initial Sp
        sp_stk_args
           | args_in_regs = stk_args_offset
           | no_load_regs = stk_args_offset
           | otherwise    = reg_call_sp_stk_args

           -- the stack args themselves
        this_call_stack_args
           | args_in_regs = reg_call_leftovers -- sp offsets are wrong
           | no_load_regs = this_call_args
           | otherwise    = reg_call_leftovers

        stack_args_size = sum (map argSize this_call_stack_args)

        overflow_regs = args_in_regs && length reg_locs > length reg_locs'

        save_extra_regs = (doc, (size,size))
          where
             -- we have extra arguments in registers to save
              extra_reg_locs = drop (length reg_locs') (reverse reg_locs)
              adj_reg_locs = [ (reg, off - adj + 1) |
                               (reg,off) <- extra_reg_locs ]
              adj = case extra_reg_locs of
                      (reg, fst_off):_ -> fst_off
              size = snd (last adj_reg_locs) + 1

              doc =
                text "Sp_adj(" <> int (-size) <> text ");" $$
                saveRegOffs adj_reg_locs $$
                loadSpWordOff "W_" 0 <> text " = " <>
                             mkApplyInfoName rest_args <> semi

        shuffle_extra_args = (doc, (shuffle_prof_stack, shuffle_norm_stack))
          where
           doc = vcat [ text "#if defined(PROFILING)",
                        shuffle_prof_doc,
                        text "#else",
                        shuffle_norm_doc,
                        text "#endif"]

           (shuffle_prof_doc, shuffle_prof_stack) = shuffle True
           (shuffle_norm_doc, shuffle_norm_stack) = shuffle False

           -- Sadly here we have to insert an stg_restore_cccs frame
           -- just underneath the stg_ap_*_info frame if we're
           -- profiling; see Note [jump_SAVE_CCCS]
           shuffle prof = (doc, -sp_adj)
             where
             sp_adj = sp_stk_args - 1 - offset
             offset = if prof then 2 else 0
             doc =
               vcat (map (shuffle_down (offset+1))
                      [sp_stk_args .. sp_stk_args+stack_args_size-1]) $$
               (if prof
                 then
                   loadSpWordOff "W_" (sp_stk_args+stack_args_size-3)
                     <> text " = stg_restore_cccs_info;" $$
                   loadSpWordOff "W_" (sp_stk_args+stack_args_size-2)
                     <> text " = CCCS;"
                 else empty) $$
               loadSpWordOff "W_" (sp_stk_args+stack_args_size-1)
                     <> text " = "
                     <> mkApplyInfoName rest_args <> semi $$
               text "Sp_adj(" <> int sp_adj <> text ");"

        shuffle_down j i =
             loadSpWordOff "W_" (i-j) <> text " = " <>
             loadSpWordOff "W_" i <> semi


-- The EXACT ARITY case
--
--      if (arity == 1) {
--          Sp++;
--          JMP_(GET_ENTRY(R1.cl));

    exact_arity_case
        = text "if (arity == " <> int n_args <> text ") {" $$
          let
             (reg_doc, sp')
                | no_load_regs || args_in_regs = (empty, stk_args_offset)
                | otherwise    = loadRegArgs regstatus stk_args_offset args
          in
          nest 4 (vcat [
--          text "TICK_SLOW_CALL_" <> text ticker <> text "_CORRECT();",
            reg_doc,
            text "Sp_adj(" <> int sp' <> text ");",
            if is_pap
                then text "R2 = " <> fun_info_label <> semi
                else empty,
            if is_fun_case then mb_tag_node n_args else empty,
            mkJump regstatus (text jump) live (if no_load_regs then [] else args) <> semi
          ])

-- The LARGER ARITY cases:
--
--      } else /* arity > 1 */ {
--          BUILD_PAP(1,0,(W_)&stg_ap_v_info);
--      }

    (larger_arity_doc, larger_arity_stack) = (doc, stack)
     where
       -- offsets in case we need to save regs:
       (reg_locs, leftovers, sp_offset)
           = assignRegs regstatus stk_args_slow_offset args
           -- BUILD_PAP assumes args start at offset 1

       stack | args_in_regs = (sp_offset, sp_offset)
             | otherwise    = (0,0)

       doc =
           text "} else {" $$
           let
             save_regs
                | args_in_regs =
                        text "Sp_adj(" <> int (-sp_offset) <> text ");" $$
                        saveRegOffs  reg_locs
                | otherwise =
                        empty
           in
           nest 4 (vcat [
--              text "TICK_SLOW_CALL_" <> text ticker <> text "_TOO_FEW();",
                save_regs,
                -- Before building the PAP, tag the function closure pointer
                if is_fun_case then
                  vcat [
                     text "if (arity < " <> int tAG_BITS_MAX <> text ") {",
                     text "  R1 = R1 + arity" <> semi,
                     text "}"
                   ]
                  else empty
                ,
                text macro <> char '(' <> int n_args <> comma <>
                                        int all_args_size <>
                                        text "," <> fun_info_label <>
                                        text "," <> text disamb <>
                                        text ");"
           ]) $$
           char '}'


-- Note [jump_SAVE_CCCS]
-- ~~~~~~~~~~~~~~~~~~~~~
-- When profiling, if we have some extra arguments to apply that we
-- save to the stack, we must also save the current cost centre stack
-- and restore it when applying the extra arguments.  This is all
-- handled by the macro jump_SAVE_CCCS(target), defined in
-- rts/AutoApply.h.
--
-- At the jump, the stack will look like this:
--
--      ... extra args ...
--      stg_ap_pp_info
--      CCCS
--      stg_restore_cccs_info

-- --------------------------------------
-- Examine tag bits of function pointer and enter it
-- directly if needed.
-- TODO: remove the redundant case in the original code.
enterFastPath regstatus no_load_regs args_in_regs args
    | Just tag <- tagForArity (length args)
    = enterFastPathHelper tag regstatus no_load_regs args_in_regs args
enterFastPath _ _ _ _ = empty

-- Copied from Constants.hs & CgUtils.hs, i'd rather have this imported:
-- (arity,tag)
tAG_BITS = (TAG_BITS :: Int)
tAG_BITS_MAX = ((1 `shiftL` tAG_BITS) :: Int)

tagForArity :: Int -> Maybe Int
tagForArity i | i < tAG_BITS_MAX = Just i
              | otherwise        = Nothing

enterFastPathHelper :: Int
                    -> RegStatus
                    -> Bool
                    -> Bool
                    -> [ArgRep]
                    -> Doc
enterFastPathHelper tag regstatus no_load_regs args_in_regs args =
  text "if (GETTAG(R1)==" <> int tag <> text ") {" $$
  nest 4 (vcat [
    reg_doc,
    text "Sp_adj(" <> int sp' <> text ");",
    -- enter, but adjust offset with tag
    mkJump regstatus (text "%GET_ENTRY(R1-" <> int tag <> text ")") ["R1"] args <> semi
  ]) $$
  text "}"
  -- I don't totally understand this code, I copied it from
  -- exact_arity_case
  -- TODO: refactor
    where
        -- offset of arguments on the stack at slow apply calls.
    stk_args_slow_offset = 1

    stk_args_offset
        | args_in_regs = 0
        | otherwise    = stk_args_slow_offset

    (reg_doc, sp')
        | no_load_regs || args_in_regs = (empty, stk_args_offset)
        | otherwise    = loadRegArgs regstatus stk_args_offset args

tickForArity arity
    | True
    = empty
    | Just tag <- tagForArity arity
    = vcat [
            text "W_[TOTAL_CALLS] = W_[TOTAL_CALLS] + 1;",
            text "W_[SLOW_CALLS_" <> int arity <> text "] = W_[SLOW_CALLS_" <> int arity <> text "] + 1;",
            text "if (TO_W_(StgFunInfoExtra_arity(%FUN_INFO(%INFO_PTR(UNTAG(R1))))) == " <> int arity <> text " ) {",
            text "  W_[RIGHT_ARITY_" <> int arity <> text "] = W_[RIGHT_ARITY_" <> int arity <> text "] + 1;",
            text "  if (GETTAG(R1)==" <> int tag <> text ") {",
            text "    W_[TAGGED_PTR_" <> int arity <> text "] = W_[TAGGED_PTR_" <> int arity <> text "] + 1;",
            text "  } else {",
            -- force a halt when not tagged!
--          text "    W_[0]=0;",
            text "  }",
            text "}"
          ]
tickForArity _ = text "W_[TOTAL_CALLS] = W_[TOTAL_CALLS] + 1;"

-- -----------------------------------------------------------------------------
-- generate an apply function

-- args is a list of 'p', 'n', 'f', 'd' or 'l'
formalParam :: ArgRep -> Int -> Doc
formalParam V _ = empty
formalParam arg n =
    formalParamType arg <> space <>
    text "arg" <> int n <> text ", "
formalParamType arg = argRep arg

argRep F   = text "F_"
argRep D   = text "D_"
argRep L   = text "L_"
argRep P   = text "gcptr"
argRep V16 = text "V16_"
argRep V32 = text "V32_"
argRep V64 = text "V64_"
argRep _   = text "W_"

genApply :: RegStatus -> [ArgRep] -> Doc
genApply regstatus args =
   let
    fun_ret_label  = mkApplyRetName args
    fun_info_label = mkApplyInfoName args
    all_args_size  = sum (map argSize args)

    (bco_doc, bco_stack) =
       genMkPAP regstatus "BUILD_PAP" "ENTRY_LBL(stg_BCO)" ["R1"] "FUN" "BCO"
             True{-stack apply-} False{-args on stack-} False{-not a PAP-}
             args all_args_size fun_info_label {- tag stmt -}False

    (fun_doc, fun_stack) =
       genMkPAP regstatus "BUILD_PAP" "%GET_ENTRY(UNTAG(R1))" ["R1"] "FUN" "FUN"
             False{-reg apply-} False{-args on stack-} False{-not a PAP-}
             args all_args_size fun_info_label {- tag stmt -}True

    (pap_doc, pap_stack) =
       genMkPAP regstatus "NEW_PAP" "stg_PAP_apply" ["R1", "R2"] "PAP" "PAP"
             True{-stack apply-} False{-args on stack-} True{-is a PAP-}
             args all_args_size fun_info_label {- tag stmt -}False

    stack_usage = maxStack [bco_stack, fun_stack, pap_stack]
   in
    vcat [
      text "INFO_TABLE_RET(" <> mkApplyName args <> text ", " <>
        text "RET_SMALL, W_ info_ptr, " <> (cat $ zipWith formalParam args [1..]) <>
        text ")\n{",
      nest 4 (vcat [
       text "W_ info;",
       text "W_ arity;",
       text "unwind Sp = Sp + WDS(" <> int (1+all_args_size) <> text ");",

--    if fast == 1:
--        print "static void *lbls[] ="
--        print "  { [FUN]             &&fun_lbl,"
--        print "    [FUN_1_0]         &&fun_lbl,"
--        print "    [FUN_0_1]        &&fun_lbl,"
--        print "    [FUN_2_0]        &&fun_lbl,"
--        print "    [FUN_1_1]        &&fun_lbl,"
--        print "    [FUN_0_2]        &&fun_lbl,"
--        print "    [FUN_STATIC]      &&fun_lbl,"
--        print "    [PAP]             &&pap_lbl,"
--        print "    [THUNK]           &&thunk_lbl,"
--        print "    [THUNK_1_0]              &&thunk_lbl,"
--        print "    [THUNK_0_1]              &&thunk_lbl,"
--        print "    [THUNK_2_0]              &&thunk_lbl,"
--        print "    [THUNK_1_1]              &&thunk_lbl,"
--        print "    [THUNK_0_2]              &&thunk_lbl,"
--        print "    [THUNK_STATIC]    &&thunk_lbl,"
--        print "    [THUNK_SELECTOR]  &&thunk_lbl,"
--        print "    [IND]            &&ind_lbl,"
--        print "    [IND_STATIC]      &&ind_lbl,"
--        print "  };"

       tickForArity (length args),
       text "",
       text "IF_DEBUG(apply,foreign \"C\" debugBelch(\"" <> fun_ret_label <>
          text "... \"); foreign \"C\" printClosure(R1 \"ptr\"));",

       text "IF_DEBUG(sanity,foreign \"C\" checkStackFrame(Sp+WDS(" <> int (1 + all_args_size)
        <> text ")\"ptr\"));",

--       text "IF_DEBUG(sanity,checkStackChunk(Sp+" <> int (1 + all_args_size) <>
--        text ", CurrentTSO->stack + CurrentTSO->stack_size));",

--       text "TICK_SLOW_CALL(" <> int (length args) <> text ");",

       let do_assert [] _ = []
           do_assert (arg:args) offset
                | isPtr arg = this : rest
                | otherwise = rest
                where this = text "ASSERT(LOOKS_LIKE_CLOSURE_PTR(Sp("
                                 <> int offset <> text ")));"
                      rest = do_assert args (offset + argSize arg)
       in
       vcat (do_assert args 1),

       text  "again:",

       -- if pointer is tagged enter it fast!
       enterFastPath regstatus False False args,

       stackCheck regstatus args False{-args on stack-}
                  fun_info_label stack_usage,

       -- Functions can be tagged, so we untag them!
       text  "R1 = UNTAG(R1);",
       text  "info = %INFO_PTR(R1);",

--    if fast == 1:
--        print "    goto *lbls[info->type];";
--    else:
        text "switch [INVALID_OBJECT .. N_CLOSURE_TYPES] (TO_W_(%INFO_TYPE(%STD_INFO(info)))) {",
        nest 4 (vcat [

--    if fast == 1:
--        print "    bco_lbl:"
--    else:
        text "case BCO: {",
        nest 4 (vcat [
          text "arity = TO_W_(StgBCO_arity(R1));",
          text "ASSERT(arity > 0);",
          bco_doc
         ]),
        text "}",

--    if fast == 1:
--        print "    fun_lbl:"
--    else:
        text "case FUN,",
        text "     FUN_1_0,",
        text "     FUN_0_1,",
        text "     FUN_2_0,",
        text "     FUN_1_1,",
        text "     FUN_0_2,",
        text "     FUN_STATIC: {",
        nest 4 (vcat [
          text "arity = TO_W_(StgFunInfoExtra_arity(%FUN_INFO(info)));",
          text "ASSERT(arity > 0);",
          fun_doc
         ]),
        text "}",

--    if fast == 1:
--        print "    pap_lbl:"
--    else:

        text "case PAP: {",
        nest 4 (vcat [
          text "arity = TO_W_(StgPAP_arity(R1));",
          text "ASSERT(arity > 0);",
          pap_doc
         ]),
        text "}",

        text "",

--    if fast == 1:
--        print "    thunk_lbl:"
--    else:
        text "case AP,",
        text "     AP_STACK,",
        text "     BLACKHOLE,",
        text "     WHITEHOLE,",
        text "     THUNK,",
        text "     THUNK_1_0,",
        text "     THUNK_0_1,",
        text "     THUNK_2_0,",
        text "     THUNK_1_1,",
        text "     THUNK_0_2,",
        text "     THUNK_STATIC,",
        text "     THUNK_SELECTOR: {",
        nest 4 (vcat [
--          text "TICK_SLOW_CALL_UNEVALD(" <> int (length args) <> text ");",
          text "Sp(0) = " <> fun_info_label <> text ";",
          -- CAREFUL! in SMP mode, the info table may already have been
          -- overwritten by an indirection, so we must enter the original
          -- info pointer we read, don't read it again, because it might
          -- not be enterable any more.
          mkJumpSaveCCCS
            regstatus (text "%ENTRY_CODE(info)") ["R1"] args <> semi,
            -- see Note [jump_SAVE_CCCS]
          text ""
         ]),
        text "}",

--    if fast == 1:
--        print "    ind_lbl:"
--    else:
        text "case IND,",
        text "     IND_STATIC: {",
        nest 4 (vcat [
          text "R1 = StgInd_indirectee(R1);",
            -- An indirection node might contain a tagged pointer
          text "goto again;"
         ]),
        text "}",
        text "",

--    if fast == 0:

       text "default: {",
       nest 4 (
         text "foreign \"C\" barf(\"" <> fun_ret_label <> text "\") never returns;"
       ),
       text "}"

        ]),
       text "}"
      ]),

      text "}"
    ]

-- -----------------------------------------------------------------------------
-- Making a fast unknown application, args are in regs

genApplyFast :: RegStatus -> [ArgRep] -> Doc
genApplyFast regstatus args =
   let
    fun_fast_label = mkApplyFastName args
    fun_ret_label  = text "RET_LBL" <> parens (mkApplyName args)
    fun_info_label = mkApplyInfoName args
    all_args_size  = sum (map argSize args)

    (fun_doc, fun_stack) =
       genMkPAP regstatus "BUILD_PAP" "%GET_ENTRY(UNTAG(R1))" ["R1"] "FUN" "FUN"
            False{-reg apply-} True{-args in regs-} False{-not a PAP-}
            args all_args_size fun_info_label {- tag stmt -}True

    (reg_locs, leftovers, sp_offset) = assignRegs regstatus 1 args

    stack_usage = maxStack [fun_stack, (sp_offset,sp_offset)]
   in
    vcat [
     fun_fast_label,
     char '{',
     nest 4 (vcat [
        text "W_ info;",
        text "W_ arity;",

        tickForArity (length args),

        -- if pointer is tagged enter it fast!
        enterFastPath regstatus False True args,

        stackCheck regstatus args True{-args in regs-}
                   fun_info_label stack_usage,

        -- Functions can be tagged, so we untag them!
        text  "R1 = UNTAG(R1);",
        text  "info = %GET_STD_INFO(R1);",
        text "switch [INVALID_OBJECT .. N_CLOSURE_TYPES] (TO_W_(%INFO_TYPE(info))) {",
        nest 4 (vcat [
          text "case FUN,",
          text "     FUN_1_0,",
          text "     FUN_0_1,",
          text "     FUN_2_0,",
          text "     FUN_1_1,",
          text "     FUN_0_2,",
          text "     FUN_STATIC: {",
          nest 4 (vcat [
            text "arity = TO_W_(StgFunInfoExtra_arity(%GET_FUN_INFO(R1)));",
            text "ASSERT(arity > 0);",
            fun_doc
           ]),
          char '}',

          text "default: {",
          nest 4 (vcat [
             text "Sp_adj" <> parens (int (-sp_offset)) <> semi,
             saveRegOffs reg_locs,
             mkJump regstatus fun_ret_label [] args <> semi
          ]),
          char '}'
        ]),

       char '}'
     ]),
     char '}'
   ]

-- -----------------------------------------------------------------------------
-- Making a stack apply

-- These little functions are like slow entry points.  They provide
-- the layer between the PAP entry code and the function's fast entry
-- point: namely they load arguments off the stack into registers (if
-- available) and jump to the function's entry code.
--
-- On entry: R1 points to the function closure
--           arguments are on the stack starting at Sp
--
-- Invariant: the list of arguments never contains void.  Since we're only
-- interested in loading arguments off the stack here, we can ignore
-- void arguments.

mkStackApplyEntryLabel:: [ArgRep] -> Doc
mkStackApplyEntryLabel args = text "stg_ap_stk_" <> text (concatMap showArg args)

genStackApply :: RegStatus -> [ArgRep] -> Doc
genStackApply regstatus args =
  let fn_entry_label = mkStackApplyEntryLabel args in
  vcat [
    fn_entry_label,
    text "{", nest 4 body, text "}"
   ]
 where
   (assign_regs, sp') = loadRegArgs regstatus 0 args
   body = vcat [assign_regs,
                text "Sp_adj" <> parens (int sp') <> semi,
                mkJump regstatus (text "%GET_ENTRY(UNTAG(R1))") ["R1"] args <> semi
                ]

-- -----------------------------------------------------------------------------
-- Stack save entry points.
--
-- These code fragments are used to save registers on the stack at a heap
-- check failure in the entry code for a function.  We also have to save R1
-- and the return address (stg_gc_fun_info) on the stack.  See __stg_gc_fun
-- in HeapStackCheck.cmm for more details.

mkStackSaveEntryLabel :: [ArgRep] -> Doc
mkStackSaveEntryLabel args = text "stg_stk_save_" <> text (concatMap showArg args)

genStackSave :: RegStatus -> [ArgRep] -> Doc
genStackSave regstatus args =
  let fn_entry_label= mkStackSaveEntryLabel args in
  vcat [
    fn_entry_label,
    text "{", nest 4 body, text "}"
   ]
 where
   body = vcat [text "Sp_adj" <> parens (int (-sp_offset)) <> semi,
                saveRegOffs reg_locs,
                text "Sp(2) = R1;",
                text "Sp(1) =" <+> int stk_args <> semi,
                text "Sp(0) = stg_gc_fun_info;",
                text "jump stg_gc_noregs [];"
                ]

   std_frame_size = 3 -- the std bits of the frame. See StgRetFun in Closures.h,
                      -- and the comment on stg_fun_gc_gen
                      -- in HeapStackCheck.cmm.
   (reg_locs, leftovers, sp_offset) = assignRegs regstatus std_frame_size args

   -- number of words of arguments on the stack.
   stk_args = sum (map argSize leftovers) + sp_offset - std_frame_size

-- -----------------------------------------------------------------------------
-- The prologue...

main = do
  args <- getArgs
  regstatus <- case args of
                 [] -> return Registerised
                 ["-u"] -> return Unregisterised
                 _other -> do hPutStrLn stderr "syntax: genapply [-u]"
                              exitWith (ExitFailure 1)
  let the_code = vcat [
                text "// DO NOT EDIT!",
                text "// Automatically generated by utils/genapply/Main.hs",
                text "",
                text "#include \"Cmm.h\"",
                text "#include \"AutoApply.h\"",
                text "",

                vcat (intersperse (text "") $
                   map (genApply regstatus) applyTypes),
                vcat (intersperse (text "") $
                   map (genStackFns regstatus) stackApplyTypes),

                vcat (intersperse (text "") $
                   map (genApplyFast regstatus) applyTypes),

                genStackApplyArray stackApplyTypes,
                genStackSaveArray stackApplyTypes,
                genBitmapArray stackApplyTypes,

                text ""  -- add a newline at the end of the file
            ]
  -- in
  putStr (render the_code)

-- These have been shown to cover about 99% of cases in practice...
applyTypes = [
        [V],
        [F],
        [D],
        [L],
        [V16],
        [V32],
        [V64],
        [N],
        [P],
        [P,V],
        [P,P],
        [P,P,V],
        [P,P,P],
        [P,P,P,V],
        [P,P,P,P],
        [P,P,P,P,P],
        [P,P,P,P,P,P]
   ]

-- No need for V args in the stack apply cases.
-- ToDo: the stack apply and stack save code doesn't make a distinction
-- between N and P (they both live in the same register), only the bitmap
-- changes, so we could share the apply/save code between lots of cases.
--
--  NOTE: other places to change if you change stackApplyTypes:
--       - rts/include/rts/storage/FunTypes.h
--       - GHC.StgToCmm.Layout: stdPattern
stackApplyTypes = [
        [],
        [N],
        [P],
        [F],
        [D],
        [L],
        [V16],
        [V32],
        [V64],
        [N,N],
        [N,P],
        [P,N],
        [P,P],
        [N,N,N],
        [N,N,P],
        [N,P,N],
        [N,P,P],
        [P,N,N],
        [P,N,P],
        [P,P,N],
        [P,P,P],
        [P,P,P,P],
        [P,P,P,P,P],
        [P,P,P,P,P,P],
        [P,P,P,P,P,P,P],
        [P,P,P,P,P,P,P,P]
   ]

genStackFns regstatus args
  =  genStackApply regstatus args
  $$ genStackSave regstatus args


genStackApplyArray types =
  vcat [
    text "section \"relrodata\" {",
    text "stg_ap_stack_entries:",
    text "W_ 0; W_ 0; W_ 0;", -- ARG_GEN, ARG_GEN_BIG, ARG_BCO
    vcat (map arr_ent types),
    text "}"
  ]
 where
  arr_ent ty = text "W_" <+> mkStackApplyEntryLabel ty <> semi

genStackSaveArray types =
  vcat [
    text "section \"relrodata\" {",
    text "stg_stack_save_entries:",
    text "W_ 0; W_ 0; W_ 0;", -- ARG_GEN, ARG_GEN_BIG, ARG_BCO
    vcat (map arr_ent types),
    text "}"
  ]
 where
  arr_ent ty = text "W_" <+> mkStackSaveEntryLabel ty <> semi

genBitmapArray :: [[ArgRep]] -> Doc
genBitmapArray types =
  vcat [
    text "section \"rodata\" {",
    text "stg_arg_bitmaps:",
    text "W_ 0; W_ 0; W_ 0;", -- ARG_GEN, ARG_GEN_BIG, ARG_BCO
    vcat (map gen_bitmap types),
    text "}"
  ]
  where
   gen_bitmap ty = text "W_" <+> int bitmap_val <> semi
        where bitmap_val =
                (fromIntegral (mkBitmap ty) `shiftL` BITMAP_BITS_SHIFT)
                 .|. sum (map argSize ty)
