/compiler/cmm/CmmParse.y

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-----------------------------------------------------------------------------
--
-- (c) The University of Glasgow, 2004-2012
--
-- Parser for concrete Cmm.
--
-----------------------------------------------------------------------------

{- -----------------------------------------------------------------------------
Note [Syntax of .cmm files]

NOTE: You are very much on your own in .cmm.  There is very little
error checking at all:

  * Type errors are detected by the (optional) -dcmm-lint pass, if you
    don't turn this on then a type error will likely result in a panic
    from the native code generator.

  * Passing the wrong number of arguments or arguments of the wrong
    type is not detected.

There are two ways to write .cmm code:

 (1) High-level Cmm code delegates the stack handling to GHC, and
     never explicitly mentions Sp or registers.

 (2) Low-level Cmm manages the stack itself, and must know about
     calling conventions.

Whether you want high-level or low-level Cmm is indicated by the
presence of an argument list on a procedure.  For example:

foo ( gcptr a, bits32 b )
{
  // this is high-level cmm code

  if (b > 0) {
     // we can make tail calls passing arguments:
     jump stg_ap_0_fast(a);
  }

  push (stg_upd_frame_info, a) {
    // stack frames can be explicitly pushed

    (x,y) = call wibble(a,b,3,4);
      // calls pass arguments and return results using the native
      // Haskell calling convention.  The code generator will automatically
      // construct a stack frame and an info table for the continuation.

    return (x,y);
      // we can return multiple values from the current proc
  }
}

bar
{
  // this is low-level cmm code, indicated by the fact that we did not
  // put an argument list on bar.

  x = R1;  // the calling convention is explicit: better be careful
           // that this works on all platforms!

  jump %ENTRY_CODE(Sp(0))
}

Here is a list of rules for high-level and low-level code.  If you
break the rules, you get a panic (for using a high-level construct in
a low-level proc), or wrong code (when using low-level code in a
high-level proc).  This stuff isn't checked! (TODO!)

High-level only:

  - tail-calls with arguments, e.g.
    jump stg_fun (arg1, arg2);

  - function calls:
    (ret1,ret2) = call stg_fun (arg1, arg2);

    This makes a call with the NativeNodeCall convention, and the
    values are returned to the following code using the NativeReturn
    convention.

  - returning:
    return (ret1, ret2)

    These use the NativeReturn convention to return zero or more
    results to the caller.

  - pushing stack frames:
    push (info_ptr, field1, ..., fieldN) { ... statements ... }

Low-level only:

  - References to Sp, R1-R8, F1-F4 etc.

    NB. foreign calls may clobber the argument registers R1-R8, F1-F4
    etc., so ensure they are saved into variables around foreign
    calls.

  - SAVE_THREAD_STATE() and LOAD_THREAD_STATE(), which modify Sp
    directly.

Both high-level and low-level code can use a raw tail-call:

    jump stg_fun [R1,R2]

This always transfers control to a low-level Cmm function, but the
call can be made from high-level code.  Arguments must be passed
explicitly in R/F/D/L registers.

NB. you *must* specify the list of GlobalRegs that are passed via a
jump, otherwise the register allocator will assume that all the
GlobalRegs are dead at the jump.


A stack frame is written like this:

INFO_TABLE_RET ( label, FRAME_TYPE, info_ptr, field1, ..., fieldN )
               return ( arg1, ..., argM )
{
  ... code ...
}

where field1 ... fieldN are the fields of the stack frame (with types)
arg1...argN are the values returned to the stack frame (with types).
The return values are assumed to be passed according to the
NativeReturn convention.

On entry to the code, the stack frame looks like:

   |----------|
   | fieldN   |
   |   ...    |
   | field1   |
   |----------|
   | info_ptr |
   |----------|
   |  argN    |
   |   ...    | <- Sp

and some of the args may be in registers.

We prepend the code by a copyIn of the args, and assign all the stack
frame fields to their formals.  The initial "arg offset" for stack
layout purposes consists of the whole stack frame plus any args that
might be on the stack.

A tail-call may pass a stack frame to the callee using the following
syntax:

jump f (info_ptr, field1,..,fieldN) (arg1,..,argN)

where info_ptr and field1..fieldN describe the stack frame, and
arg1..argN are the arguments passed to f using the NativeNodeCall
convention.

----------------------------------------------------------------------------- -}

{
{-# LANGUAGE BangPatterns #-} -- required for versions of Happy before 1.18.6
{-# OPTIONS -Wwarn -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/Commentary/CodingStyle#Warnings
-- for details

module CmmParse ( parseCmmFile ) where

import StgCmmExtCode
import CmmCallConv
import StgCmmProf
import StgCmmHeap
import StgCmmMonad hiding ( getCode, getCodeR, emitLabel, emit, emitStore
                          , emitAssign, emitOutOfLine, withUpdFrameOff
                          , getUpdFrameOff )
import qualified StgCmmMonad as F
import StgCmmUtils
import StgCmmForeign
import StgCmmExpr
import StgCmmClosure
import StgCmmLayout     hiding (ArgRep(..))
import StgCmmTicky
import StgCmmBind       ( emitBlackHoleCode, emitUpdateFrame )

import MkGraph
import Cmm
import CmmUtils
import CmmInfo
import BlockId
import CmmLex
import CLabel
import SMRep
import Lexer

import CostCentre
import ForeignCall
import Module
import Platform
import Literal
import Unique
import UniqFM
import SrcLoc
import DynFlags
import StaticFlags
import ErrUtils
import StringBuffer
import FastString
import Panic
import Constants
import Outputable
import BasicTypes
import Bag              ( emptyBag, unitBag )
import Var

import Control.Monad
import Data.Array
import Data.Char        ( ord )
import System.Exit
import Data.Maybe

#include "HsVersions.h"
}

%expect 0

%token
        ':'     { L _ (CmmT_SpecChar ':') }
        ';'     { L _ (CmmT_SpecChar ';') }
        '{'     { L _ (CmmT_SpecChar '{') }
        '}'     { L _ (CmmT_SpecChar '}') }
        '['     { L _ (CmmT_SpecChar '[') }
        ']'     { L _ (CmmT_SpecChar ']') }
        '('     { L _ (CmmT_SpecChar '(') }
        ')'     { L _ (CmmT_SpecChar ')') }
        '='     { L _ (CmmT_SpecChar '=') }
        '`'     { L _ (CmmT_SpecChar '`') }
        '~'     { L _ (CmmT_SpecChar '~') }
        '/'     { L _ (CmmT_SpecChar '/') }
        '*'     { L _ (CmmT_SpecChar '*') }
        '%'     { L _ (CmmT_SpecChar '%') }
        '-'     { L _ (CmmT_SpecChar '-') }
        '+'     { L _ (CmmT_SpecChar '+') }
        '&'     { L _ (CmmT_SpecChar '&') }
        '^'     { L _ (CmmT_SpecChar '^') }
        '|'     { L _ (CmmT_SpecChar '|') }
        '>'     { L _ (CmmT_SpecChar '>') }
        '<'     { L _ (CmmT_SpecChar '<') }
        ','     { L _ (CmmT_SpecChar ',') }
        '!'     { L _ (CmmT_SpecChar '!') }

        '..'    { L _ (CmmT_DotDot) }
        '::'    { L _ (CmmT_DoubleColon) }
        '>>'    { L _ (CmmT_Shr) }
        '<<'    { L _ (CmmT_Shl) }
        '>='    { L _ (CmmT_Ge) }
        '<='    { L _ (CmmT_Le) }
        '=='    { L _ (CmmT_Eq) }
        '!='    { L _ (CmmT_Ne) }
        '&&'    { L _ (CmmT_BoolAnd) }
        '||'    { L _ (CmmT_BoolOr) }

        'CLOSURE'       { L _ (CmmT_CLOSURE) }
        'INFO_TABLE'    { L _ (CmmT_INFO_TABLE) }
        'INFO_TABLE_RET'{ L _ (CmmT_INFO_TABLE_RET) }
        'INFO_TABLE_FUN'{ L _ (CmmT_INFO_TABLE_FUN) }
        'INFO_TABLE_CONSTR'{ L _ (CmmT_INFO_TABLE_CONSTR) }
        'INFO_TABLE_SELECTOR'{ L _ (CmmT_INFO_TABLE_SELECTOR) }
        'else'          { L _ (CmmT_else) }
        'export'        { L _ (CmmT_export) }
        'section'       { L _ (CmmT_section) }
        'align'         { L _ (CmmT_align) }
        'goto'          { L _ (CmmT_goto) }
        'if'            { L _ (CmmT_if) }
        'call'          { L _ (CmmT_call) }
        'jump'          { L _ (CmmT_jump) }
        'foreign'       { L _ (CmmT_foreign) }
        'never'         { L _ (CmmT_never) }
        'prim'          { L _ (CmmT_prim) }
        'return'        { L _ (CmmT_return) }
        'returns'       { L _ (CmmT_returns) }
        'import'        { L _ (CmmT_import) }
        'switch'        { L _ (CmmT_switch) }
        'case'          { L _ (CmmT_case) }
        'default'       { L _ (CmmT_default) }
        'push'          { L _ (CmmT_push) }
        'bits8'         { L _ (CmmT_bits8) }
        'bits16'        { L _ (CmmT_bits16) }
        'bits32'        { L _ (CmmT_bits32) }
        'bits64'        { L _ (CmmT_bits64) }
        'bits128'       { L _ (CmmT_bits128) }
        'float32'       { L _ (CmmT_float32) }
        'float64'       { L _ (CmmT_float64) }
        'gcptr'         { L _ (CmmT_gcptr) }

        GLOBALREG       { L _ (CmmT_GlobalReg   $$) }
        NAME            { L _ (CmmT_Name        $$) }
        STRING          { L _ (CmmT_String      $$) }
        INT             { L _ (CmmT_Int         $$) }
        FLOAT           { L _ (CmmT_Float       $$) }

%monad { P } { >>= } { return }
%lexer { cmmlex } { L _ CmmT_EOF }
%name cmmParse cmm
%tokentype { Located CmmToken }

-- C-- operator precedences, taken from the C-- spec
%right '||'     -- non-std extension, called %disjoin in C--
%right '&&'     -- non-std extension, called %conjoin in C--
%right '!'
%nonassoc '>=' '>' '<=' '<' '!=' '=='
%left '|'
%left '^'
%left '&'
%left '>>' '<<'
%left '-' '+'
%left '/' '*' '%'
%right '~'

%%

cmm     :: { CmmParse () }
        : {- empty -}                   { return () }
        | cmmtop cmm                    { do $1; $2 }

cmmtop  :: { CmmParse () }
        : cmmproc                       { $1 }
        | cmmdata                       { $1 }
        | decl                          { $1 } 
        | 'CLOSURE' '(' NAME ',' NAME lits ')' ';'  
                {% withThisPackage $ \pkg -> 
                   do lits <- sequence $6;
                      staticClosure pkg $3 $5 (map getLit lits) }

-- The only static closures in the RTS are dummy closures like
-- stg_END_TSO_QUEUE_closure and stg_dummy_ret.  We don't need
-- to provide the full generality of static closures here.
-- In particular:
--      * CCS can always be CCS_DONT_CARE
--      * closure is always extern
--      * payload is always empty
--      * we can derive closure and info table labels from a single NAME

cmmdata :: { CmmParse () }
        : 'section' STRING '{' data_label statics '}' 
                { do lbl <- $4;
                     ss <- sequence $5;
                     code (emitDecl (CmmData (section $2) (Statics lbl $ concat ss))) }

data_label :: { CmmParse CLabel }
    : NAME ':'  
                {% withThisPackage $ \pkg -> 
                   return (mkCmmDataLabel pkg $1) }

statics :: { [CmmParse [CmmStatic]] }
        : {- empty -}                   { [] }
        | static statics                { $1 : $2 }
    
-- Strings aren't used much in the RTS HC code, so it doesn't seem
-- worth allowing inline strings.  C-- doesn't allow them anyway.
static  :: { CmmParse [CmmStatic] }
        : type expr ';' { do e <- $2;
                             return [CmmStaticLit (getLit e)] }
        | type ';'                      { return [CmmUninitialised
                                                        (widthInBytes (typeWidth $1))] }
        | 'bits8' '[' ']' STRING ';'    { return [mkString $4] }
        | 'bits8' '[' INT ']' ';'       { return [CmmUninitialised 
                                                        (fromIntegral $3)] }
        | typenot8 '[' INT ']' ';'      { return [CmmUninitialised 
                                                (widthInBytes (typeWidth $1) * 
                                                        fromIntegral $3)] }
        | 'CLOSURE' '(' NAME lits ')'
                { do { lits <- sequence $4
                ; dflags <- getDynFlags
                     ; return $ map CmmStaticLit $
                        mkStaticClosure dflags (mkForeignLabel $3 Nothing ForeignLabelInExternalPackage IsData)
                         -- mkForeignLabel because these are only used
                         -- for CHARLIKE and INTLIKE closures in the RTS.
                        dontCareCCS (map getLit lits) [] [] [] } }
        -- arrays of closures required for the CHARLIKE & INTLIKE arrays

lits    :: { [CmmParse CmmExpr] }
        : {- empty -}           { [] }
        | ',' expr lits         { $2 : $3 }

cmmproc :: { CmmParse () }
        : info maybe_conv maybe_formals maybe_body
                { do ((entry_ret_label, info, stk_formals, formals), agraph) <-
                       getCodeR $ loopDecls $ do {
                         (entry_ret_label, info, stk_formals) <- $1;
                         formals <- sequence (fromMaybe [] $3);
                         $4;
                         return (entry_ret_label, info, stk_formals, formals) }
                     let do_layout = isJust $3
                     code (emitProcWithStackFrame $2 info
                                entry_ret_label stk_formals formals agraph
                                do_layout ) }

maybe_conv :: { Convention }
           : {- empty -}        { NativeNodeCall }
           | 'return'           { NativeReturn }

maybe_body :: { CmmParse () }
           : ';'                { return () }
           | '{' body '}'       { $2 }

info    :: { CmmParse (CLabel, Maybe CmmInfoTable, [LocalReg]) }
        : NAME
                {% withThisPackage $ \pkg ->
                   do   newFunctionName $1 pkg
                        return (mkCmmCodeLabel pkg $1, Nothing, []) }


        | 'INFO_TABLE' '(' NAME ',' INT ',' INT ',' INT ',' STRING ',' STRING ')'
                -- ptrs, nptrs, closure type, description, type
                {% withThisPackage $ \pkg ->
                   do dflags <- getDynFlags
                      let prof = profilingInfo dflags $11 $13
                          rep  = mkRTSRep (fromIntegral $9) $
                                   mkHeapRep dflags False (fromIntegral $5)
                                                   (fromIntegral $7) Thunk
                              -- not really Thunk, but that makes the info table
                              -- we want.
                      return (mkCmmEntryLabel pkg $3,
                              Just $ CmmInfoTable { cit_lbl = mkCmmInfoLabel pkg $3
                                           , cit_rep = rep
                                           , cit_prof = prof, cit_srt = NoC_SRT },
                              []) }
        
        | 'INFO_TABLE_FUN' '(' NAME ',' INT ',' INT ',' INT ',' STRING ',' STRING ',' INT ')'
                -- ptrs, nptrs, closure type, description, type, fun type
                {% withThisPackage $ \pkg -> 
                   do dflags <- getDynFlags
                      let prof = profilingInfo dflags $11 $13
                          ty   = Fun 0 (ArgSpec (fromIntegral $15))
                                -- Arity zero, arg_type $15
                          rep = mkRTSRep (fromIntegral $9) $
                                    mkHeapRep dflags False (fromIntegral $5)
                                                    (fromIntegral $7) ty
                      return (mkCmmEntryLabel pkg $3,
                              Just $ CmmInfoTable { cit_lbl = mkCmmInfoLabel pkg $3
                                           , cit_rep = rep
                                           , cit_prof = prof, cit_srt = NoC_SRT },
                              []) }
                -- we leave most of the fields zero here.  This is only used
                -- to generate the BCO info table in the RTS at the moment.

        | 'INFO_TABLE_CONSTR' '(' NAME ',' INT ',' INT ',' INT ',' INT ',' STRING ',' STRING ')'
                -- ptrs, nptrs, tag, closure type, description, type
                {% withThisPackage $ \pkg ->
                   do dflags <- getDynFlags
                      let prof = profilingInfo dflags $13 $15
                          ty  = Constr (fromIntegral $9)  -- Tag
                                       (stringToWord8s $13)
                          rep = mkRTSRep (fromIntegral $11) $
                                  mkHeapRep dflags False (fromIntegral $5)
                                                  (fromIntegral $7) ty
                      return (mkCmmEntryLabel pkg $3,
                              Just $ CmmInfoTable { cit_lbl = mkCmmInfoLabel pkg $3
                                           , cit_rep = rep
                                           , cit_prof = prof, cit_srt = NoC_SRT },
                              []) }

                     -- If profiling is on, this string gets duplicated,
                     -- but that's the way the old code did it we can fix it some other time.
        
        | 'INFO_TABLE_SELECTOR' '(' NAME ',' INT ',' INT ',' STRING ',' STRING ')'
                -- selector, closure type, description, type
                {% withThisPackage $ \pkg ->
                   do dflags <- getDynFlags
                      let prof = profilingInfo dflags $9 $11
                          ty  = ThunkSelector (fromIntegral $5)
                          rep = mkRTSRep (fromIntegral $7) $
                                   mkHeapRep dflags False 0 0 ty
                      return (mkCmmEntryLabel pkg $3,
                              Just $ CmmInfoTable { cit_lbl = mkCmmInfoLabel pkg $3
                                           , cit_rep = rep
                                           , cit_prof = prof, cit_srt = NoC_SRT },
                              []) }

        | 'INFO_TABLE_RET' '(' NAME ',' INT ')'
                -- closure type (no live regs)
                {% withThisPackage $ \pkg ->
                   do let prof = NoProfilingInfo
                          rep  = mkRTSRep (fromIntegral $5) $ mkStackRep []
                      return (mkCmmRetLabel pkg $3,
                              Just $ CmmInfoTable { cit_lbl = mkCmmRetInfoLabel pkg $3
                                           , cit_rep = rep
                                           , cit_prof = prof, cit_srt = NoC_SRT },
                              []) }

        | 'INFO_TABLE_RET' '(' NAME ',' INT ',' formals0 ')'
                -- closure type, live regs
                {% withThisPackage $ \pkg ->
                   do dflags <- getDynFlags
                      live <- sequence $7
                      let prof = NoProfilingInfo
                          -- drop one for the info pointer
                          bitmap = mkLiveness dflags (map Just (drop 1 live))
                          rep  = mkRTSRep (fromIntegral $5) $ mkStackRep bitmap
                      return (mkCmmRetLabel pkg $3,
                              Just $ CmmInfoTable { cit_lbl = mkCmmRetInfoLabel pkg $3
                                           , cit_rep = rep
                                           , cit_prof = prof, cit_srt = NoC_SRT },
                              live) }

body    :: { CmmParse () }
        : {- empty -}                   { return () }
        | decl body                     { do $1; $2 }
        | stmt body                     { do $1; $2 }

decl    :: { CmmParse () }
        : type names ';'                { mapM_ (newLocal $1) $2 }
        | 'import' importNames ';'      { mapM_ newImport $2 }
        | 'export' names ';'            { return () }  -- ignore exports


-- an imported function name, with optional packageId
importNames
        :: { [(FastString, CLabel)] }
        : importName                    { [$1] }
        | importName ',' importNames    { $1 : $3 }

importName
        :: { (FastString,  CLabel) }

        -- A label imported without an explicit packageId.
        --      These are taken to come frome some foreign, unnamed package.
        : NAME  
        { ($1, mkForeignLabel $1 Nothing ForeignLabelInExternalPackage IsFunction) }

        -- A label imported with an explicit packageId.
        | STRING NAME
        { ($2, mkCmmCodeLabel (fsToPackageId (mkFastString $1)) $2) }
        
        
names   :: { [FastString] }
        : NAME                          { [$1] }
        | NAME ',' names                { $1 : $3 }

stmt    :: { CmmParse () }
        : ';'                                   { return () }

        | NAME ':'
                { do l <- newLabel $1; emitLabel l }



        | lreg '=' expr ';'
                { do reg <- $1; e <- $3; emitAssign reg e }
        | type '[' expr ']' '=' expr ';'
                { doStore $1 $3 $6 }

        -- Gah! We really want to say "foreign_results" but that causes
        -- a shift/reduce conflict with assignment.  We either
        -- we expand out the no-result and single result cases or
        -- we tweak the syntax to avoid the conflict.  The later
        -- option is taken here because the other way would require
        -- multiple levels of expanding and get unwieldy.
        | foreign_results 'foreign' STRING foreignLabel '(' cmm_hint_exprs0 ')' safety opt_never_returns ';'
                {% foreignCall $3 $1 $4 $6 $8 $9 }
        | foreign_results 'prim' '%' NAME '(' exprs0 ')' ';'
                {% primCall $1 $4 $6 }
        -- stmt-level macros, stealing syntax from ordinary C-- function calls.
        -- Perhaps we ought to use the %%-form?
        | NAME '(' exprs0 ')' ';'
                {% stmtMacro $1 $3  }
        | 'switch' maybe_range expr '{' arms default '}'
                { do as <- sequence $5; doSwitch $2 $3 as $6 }
        | 'goto' NAME ';'
                { do l <- lookupLabel $2; emit (mkBranch l) }
        | 'return' '(' exprs0 ')' ';'
                { doReturn $3 }
        | 'jump' expr vols ';'
                { doRawJump $2 $3 }
        | 'jump' expr '(' exprs0 ')' ';'
                { doJumpWithStack $2 [] $4 }
        | 'jump' expr '(' exprs0 ')' '(' exprs0 ')' ';'
                { doJumpWithStack $2 $4 $7 }
        | 'call' expr '(' exprs0 ')' ';'
                { doCall $2 [] $4 }
        | '(' formals ')' '=' 'call' expr '(' exprs0 ')' ';'
                { doCall $6 $2 $8 }
        | 'if' bool_expr 'goto' NAME
                { do l <- lookupLabel $4; cmmRawIf $2 l }
        | 'if' bool_expr '{' body '}' else      
                { cmmIfThenElse $2 $4 $6 }
        | 'push' '(' exprs0 ')' maybe_body
                { pushStackFrame $3 $5 }

foreignLabel     :: { CmmParse CmmExpr }
        : NAME                          { return (CmmLit (CmmLabel (mkForeignLabel $1 Nothing ForeignLabelInExternalPackage IsFunction))) }

opt_never_returns :: { CmmReturnInfo }
        :                               { CmmMayReturn }
        | 'never' 'returns'             { CmmNeverReturns }

bool_expr :: { CmmParse BoolExpr }
        : bool_op                       { $1 }
        | expr                          { do e <- $1; return (BoolTest e) }

bool_op :: { CmmParse BoolExpr }
        : bool_expr '&&' bool_expr      { do e1 <- $1; e2 <- $3; 
                                          return (BoolAnd e1 e2) }
        | bool_expr '||' bool_expr      { do e1 <- $1; e2 <- $3; 
                                          return (BoolOr e1 e2)  }
        | '!' bool_expr                 { do e <- $2; return (BoolNot e) }
        | '(' bool_op ')'               { $2 }

safety  :: { Safety }
        : {- empty -}                   { PlayRisky }
        | STRING                        {% parseSafety $1 }

vols    :: { [GlobalReg] }
        : '[' ']'                       { [] }
        | '[' '*' ']'                   {% do df <- getDynFlags
                                         ; return (realArgRegsCover df) }
                                           -- All of them. See comment attached
                                           -- to realArgRegsCover
        | '[' globals ']'               { $2 }

globals :: { [GlobalReg] }
        : GLOBALREG                     { [$1] }
        | GLOBALREG ',' globals         { $1 : $3 }

maybe_range :: { Maybe (Int,Int) }
        : '[' INT '..' INT ']'  { Just (fromIntegral $2, fromIntegral $4) }
        | {- empty -}           { Nothing }

arms    :: { [CmmParse ([Int],Either BlockId (CmmParse ()))] }
        : {- empty -}                   { [] }
        | arm arms                      { $1 : $2 }

arm     :: { CmmParse ([Int],Either BlockId (CmmParse ())) }
        : 'case' ints ':' arm_body      { do b <- $4; return ($2, b) }

arm_body :: { CmmParse (Either BlockId (CmmParse ())) }
        : '{' body '}'                  { return (Right $2) }
        | 'goto' NAME ';'               { do l <- lookupLabel $2; return (Left l) }

ints    :: { [Int] }
        : INT                           { [ fromIntegral $1 ] }
        | INT ',' ints                  { fromIntegral $1 : $3 }

default :: { Maybe (CmmParse ()) }
        : 'default' ':' '{' body '}'    { Just $4 }
        -- taking a few liberties with the C-- syntax here; C-- doesn't have
        -- 'default' branches
        | {- empty -}                   { Nothing }

-- Note: OldCmm doesn't support a first class 'else' statement, though
-- CmmNode does.
else    :: { CmmParse () }
        : {- empty -}                   { return () }
        | 'else' '{' body '}'           { $3 }

-- we have to write this out longhand so that Happy's precedence rules
-- can kick in.
expr    :: { CmmParse CmmExpr }
        : expr '/' expr                 { mkMachOp MO_U_Quot [$1,$3] }
        | expr '*' expr                 { mkMachOp MO_Mul [$1,$3] }
        | expr '%' expr                 { mkMachOp MO_U_Rem [$1,$3] }
        | expr '-' expr                 { mkMachOp MO_Sub [$1,$3] }
        | expr '+' expr                 { mkMachOp MO_Add [$1,$3] }
        | expr '>>' expr                { mkMachOp MO_U_Shr [$1,$3] }
        | expr '<<' expr                { mkMachOp MO_Shl [$1,$3] }
        | expr '&' expr                 { mkMachOp MO_And [$1,$3] }
        | expr '^' expr                 { mkMachOp MO_Xor [$1,$3] }
        | expr '|' expr                 { mkMachOp MO_Or [$1,$3] }
        | expr '>=' expr                { mkMachOp MO_U_Ge [$1,$3] }
        | expr '>' expr                 { mkMachOp MO_U_Gt [$1,$3] }
        | expr '<=' expr                { mkMachOp MO_U_Le [$1,$3] }
        | expr '<' expr                 { mkMachOp MO_U_Lt [$1,$3] }
        | expr '!=' expr                { mkMachOp MO_Ne [$1,$3] }
        | expr '==' expr                { mkMachOp MO_Eq [$1,$3] }
        | '~' expr                      { mkMachOp MO_Not [$2] }
        | '-' expr                      { mkMachOp MO_S_Neg [$2] }
        | expr0 '`' NAME '`' expr0      {% do { mo <- nameToMachOp $3 ;
                                                return (mkMachOp mo [$1,$5]) } }
        | expr0                         { $1 }

expr0   :: { CmmParse CmmExpr }
        : INT   maybe_ty         { return (CmmLit (CmmInt $1 (typeWidth $2))) }
        | FLOAT maybe_ty         { return (CmmLit (CmmFloat $1 (typeWidth $2))) }
        | STRING                 { do s <- code (newStringCLit $1); 
                                      return (CmmLit s) }
        | reg                    { $1 }
        | type '[' expr ']'      { do e <- $3; return (CmmLoad e $1) }
        | '%' NAME '(' exprs0 ')' {% exprOp $2 $4 }
        | '(' expr ')'           { $2 }


-- leaving out the type of a literal gives you the native word size in C--
maybe_ty :: { CmmType }
        : {- empty -}                   {% do dflags <- getDynFlags; return $ bWord dflags }
        | '::' type                     { $2 }

cmm_hint_exprs0 :: { [CmmParse (CmmExpr, ForeignHint)] }
        : {- empty -}                   { [] }
        | cmm_hint_exprs                { $1 }

cmm_hint_exprs :: { [CmmParse (CmmExpr, ForeignHint)] }
        : cmm_hint_expr                 { [$1] }
        | cmm_hint_expr ',' cmm_hint_exprs      { $1 : $3 }

cmm_hint_expr :: { CmmParse (CmmExpr, ForeignHint) }
        : expr                          { do e <- $1;
                                             return (e, inferCmmHint e) }
        | expr STRING                   {% do h <- parseCmmHint $2;
                                              return $ do
                                                e <- $1; return (e, h) }

exprs0  :: { [CmmParse CmmExpr] }
        : {- empty -}                   { [] }
        | exprs                         { $1 }

exprs   :: { [CmmParse CmmExpr] }
        : expr                          { [ $1 ] }
        | expr ',' exprs                { $1 : $3 }

reg     :: { CmmParse CmmExpr }
        : NAME                  { lookupName $1 }
        | GLOBALREG             { return (CmmReg (CmmGlobal $1)) }

foreign_results :: { [CmmParse (LocalReg, ForeignHint)] }
        : {- empty -}                   { [] }
        | '(' foreign_formals ')' '='   { $2 }

foreign_formals :: { [CmmParse (LocalReg, ForeignHint)] }
        : foreign_formal                        { [$1] }
        | foreign_formal ','                    { [$1] }
        | foreign_formal ',' foreign_formals    { $1 : $3 }

foreign_formal :: { CmmParse (LocalReg, ForeignHint) }
        : local_lreg            { do e <- $1; return (e, (inferCmmHint (CmmReg (CmmLocal e)))) }
        | STRING local_lreg     {% do h <- parseCmmHint $1;
                                      return $ do
                                         e <- $2; return (e,h) }

local_lreg :: { CmmParse LocalReg }
        : NAME                  { do e <- lookupName $1;
                                     return $
                                       case e of 
                                        CmmReg (CmmLocal r) -> r
                                        other -> pprPanic "CmmParse:" (ftext $1 <> text " not a local register") }

lreg    :: { CmmParse CmmReg }
        : NAME                  { do e <- lookupName $1;
                                     return $
                                       case e of 
                                        CmmReg r -> r
                                        other -> pprPanic "CmmParse:" (ftext $1 <> text " not a register") }
        | GLOBALREG             { return (CmmGlobal $1) }

maybe_formals :: { Maybe [CmmParse LocalReg] }
        : {- empty -}           { Nothing }
        | '(' formals0 ')'      { Just $2 }

formals0 :: { [CmmParse LocalReg] }
        : {- empty -}           { [] }
        | formals               { $1 }

formals :: { [CmmParse LocalReg] }
        : formal ','            { [$1] }
        | formal                { [$1] }
        | formal ',' formals       { $1 : $3 }

formal :: { CmmParse LocalReg }
        : type NAME             { newLocal $1 $2 }

type    :: { CmmType }
        : 'bits8'               { b8 }
        | typenot8              { $1 }

typenot8 :: { CmmType }
        : 'bits16'              { b16 }
        | 'bits32'              { b32 }
        | 'bits64'              { b64 }
        | 'bits128'             { b128 }
        | 'float32'             { f32 }
        | 'float64'             { f64 }
        | 'gcptr'               {% do dflags <- getDynFlags; return $ gcWord dflags }

{
section :: String -> Section
section "text"      = Text
section "data"      = Data
section "rodata"    = ReadOnlyData
section "relrodata" = RelocatableReadOnlyData
section "bss"       = UninitialisedData
section s           = OtherSection s

mkString :: String -> CmmStatic
mkString s = CmmString (map (fromIntegral.ord) s)

-- |
-- Given an info table, decide what the entry convention for the proc
-- is.  That is, for an INFO_TABLE_RET we want the return convention,
-- otherwise it is a NativeNodeCall.
--
infoConv :: Maybe CmmInfoTable -> Convention
infoConv Nothing = NativeNodeCall
infoConv (Just info)
  | isStackRep (cit_rep info) = NativeReturn
  | otherwise                 = NativeNodeCall

-- mkMachOp infers the type of the MachOp from the type of its first
-- argument.  We assume that this is correct: for MachOps that don't have
-- symmetrical args (e.g. shift ops), the first arg determines the type of
-- the op.
mkMachOp :: (Width -> MachOp) -> [CmmParse CmmExpr] -> CmmParse CmmExpr
mkMachOp fn args = do
  dflags <- getDynFlags
  arg_exprs <- sequence args
  return (CmmMachOp (fn (typeWidth (cmmExprType dflags (head arg_exprs)))) arg_exprs)

getLit :: CmmExpr -> CmmLit
getLit (CmmLit l) = l
getLit (CmmMachOp (MO_S_Neg _) [CmmLit (CmmInt i r)])  = CmmInt (negate i) r
getLit _ = panic "invalid literal" -- TODO messy failure

nameToMachOp :: FastString -> P (Width -> MachOp)
nameToMachOp name =
  case lookupUFM machOps name of
        Nothing -> fail ("unknown primitive " ++ unpackFS name)
        Just m  -> return m

exprOp :: FastString -> [CmmParse CmmExpr] -> P (CmmParse CmmExpr)
exprOp name args_code = do
  dflags <- getDynFlags
  case lookupUFM (exprMacros dflags) name of
     Just f  -> return $ do
        args <- sequence args_code
        return (f args)
     Nothing -> do
        mo <- nameToMachOp name
        return $ mkMachOp mo args_code

exprMacros :: DynFlags -> UniqFM ([CmmExpr] -> CmmExpr)
exprMacros dflags = listToUFM [
  ( fsLit "ENTRY_CODE",   \ [x] -> entryCode dflags x ),
  ( fsLit "INFO_PTR",     \ [x] -> closureInfoPtr dflags x ),
  ( fsLit "STD_INFO",     \ [x] -> infoTable dflags x ),
  ( fsLit "FUN_INFO",     \ [x] -> funInfoTable dflags x ),
  ( fsLit "GET_ENTRY",    \ [x] -> entryCode dflags (closureInfoPtr dflags x) ),
  ( fsLit "GET_STD_INFO", \ [x] -> infoTable dflags (closureInfoPtr dflags x) ),
  ( fsLit "GET_FUN_INFO", \ [x] -> funInfoTable dflags (closureInfoPtr dflags x) ),
  ( fsLit "INFO_TYPE",    \ [x] -> infoTableClosureType dflags x ),
  ( fsLit "INFO_PTRS",    \ [x] -> infoTablePtrs dflags x ),
  ( fsLit "INFO_NPTRS",   \ [x] -> infoTableNonPtrs dflags x )
  ]

-- we understand a subset of C-- primitives:
machOps = listToUFM $
        map (\(x, y) -> (mkFastString x, y)) [
        ( "add",        MO_Add ),
        ( "sub",        MO_Sub ),
        ( "eq",         MO_Eq ),
        ( "ne",         MO_Ne ),
        ( "mul",        MO_Mul ),
        ( "neg",        MO_S_Neg ),
        ( "quot",       MO_S_Quot ),
        ( "rem",        MO_S_Rem ),
        ( "divu",       MO_U_Quot ),
        ( "modu",       MO_U_Rem ),

        ( "ge",         MO_S_Ge ),
        ( "le",         MO_S_Le ),
        ( "gt",         MO_S_Gt ),
        ( "lt",         MO_S_Lt ),

        ( "geu",        MO_U_Ge ),
        ( "leu",        MO_U_Le ),
        ( "gtu",        MO_U_Gt ),
        ( "ltu",        MO_U_Lt ),

        ( "and",        MO_And ),
        ( "or",         MO_Or ),
        ( "xor",        MO_Xor ),
        ( "com",        MO_Not ),
        ( "shl",        MO_Shl ),
        ( "shrl",       MO_U_Shr ),
        ( "shra",       MO_S_Shr ),

        ( "fadd",       MO_F_Add ),
        ( "fsub",       MO_F_Sub ),
        ( "fneg",       MO_F_Neg ),
        ( "fmul",       MO_F_Mul ),
        ( "fquot",      MO_F_Quot ),

        ( "feq",        MO_F_Eq ),
        ( "fne",        MO_F_Ne ),
        ( "fge",        MO_F_Ge ),
        ( "fle",        MO_F_Le ),
        ( "fgt",        MO_F_Gt ),
        ( "flt",        MO_F_Lt ),

        ( "lobits8",  flip MO_UU_Conv W8  ),
        ( "lobits16", flip MO_UU_Conv W16 ),
        ( "lobits32", flip MO_UU_Conv W32 ),
        ( "lobits64", flip MO_UU_Conv W64 ),

        ( "zx16",     flip MO_UU_Conv W16 ),
        ( "zx32",     flip MO_UU_Conv W32 ),
        ( "zx64",     flip MO_UU_Conv W64 ),

        ( "sx16",     flip MO_SS_Conv W16 ),
        ( "sx32",     flip MO_SS_Conv W32 ),
        ( "sx64",     flip MO_SS_Conv W64 ),

        ( "f2f32",    flip MO_FF_Conv W32 ),  -- TODO; rounding mode
        ( "f2f64",    flip MO_FF_Conv W64 ),  -- TODO; rounding mode
        ( "f2i8",     flip MO_FS_Conv W8 ),
        ( "f2i16",    flip MO_FS_Conv W16 ),
        ( "f2i32",    flip MO_FS_Conv W32 ),
        ( "f2i64",    flip MO_FS_Conv W64 ),
        ( "i2f32",    flip MO_SF_Conv W32 ),
        ( "i2f64",    flip MO_SF_Conv W64 )
        ]

callishMachOps = listToUFM $
        map (\(x, y) -> (mkFastString x, y)) [
        ( "write_barrier", MO_WriteBarrier ),
        ( "memcpy", MO_Memcpy ),
        ( "memset", MO_Memset ),
        ( "memmove", MO_Memmove )
        -- ToDo: the rest, maybe
    ]

parseSafety :: String -> P Safety
parseSafety "safe"   = return PlaySafe
parseSafety "unsafe" = return PlayRisky
parseSafety "interruptible" = return PlayInterruptible
parseSafety str      = fail ("unrecognised safety: " ++ str)

parseCmmHint :: String -> P ForeignHint
parseCmmHint "ptr"    = return AddrHint
parseCmmHint "signed" = return SignedHint
parseCmmHint str      = fail ("unrecognised hint: " ++ str)

-- labels are always pointers, so we might as well infer the hint
inferCmmHint :: CmmExpr -> ForeignHint
inferCmmHint (CmmLit (CmmLabel _)) = AddrHint
inferCmmHint (CmmReg (CmmGlobal g)) | isPtrGlobalReg g = AddrHint
inferCmmHint _ = NoHint

isPtrGlobalReg Sp                    = True
isPtrGlobalReg SpLim                 = True
isPtrGlobalReg Hp                    = True
isPtrGlobalReg HpLim                 = True
isPtrGlobalReg CCCS                  = True
isPtrGlobalReg CurrentTSO            = True
isPtrGlobalReg CurrentNursery        = True
isPtrGlobalReg (VanillaReg _ VGcPtr) = True
isPtrGlobalReg _                     = False

happyError :: P a
happyError = srcParseFail

-- -----------------------------------------------------------------------------
-- Statement-level macros

stmtMacro :: FastString -> [CmmParse CmmExpr] -> P (CmmParse ())
stmtMacro fun args_code = do
  case lookupUFM stmtMacros fun of
    Nothing -> fail ("unknown macro: " ++ unpackFS fun)
    Just fcode -> return $ do
        args <- sequence args_code
        code (fcode args)

stmtMacros :: UniqFM ([CmmExpr] -> FCode ())
stmtMacros = listToUFM [
  ( fsLit "CCS_ALLOC",             \[words,ccs]  -> profAlloc words ccs ),
  ( fsLit "ENTER_CCS_THUNK",       \[e] -> enterCostCentreThunk e ),

  ( fsLit "CLOSE_NURSERY",         \[]  -> emitCloseNursery ),
  ( fsLit "OPEN_NURSERY",          \[]  -> emitOpenNursery ),

  -- completely generic heap and stack checks, for use in high-level cmm.
  ( fsLit "HP_CHK_GEN",            \[bytes] ->
                                      heapStackCheckGen Nothing (Just bytes) ),
  ( fsLit "STK_CHK_GEN",           \[] ->
                                      heapStackCheckGen (Just (CmmLit CmmHighStackMark)) Nothing ),

  -- A stack check for a fixed amount of stack.  Sounds a bit strange, but
  -- we use the stack for a bit of temporary storage in a couple of primops
  ( fsLit "STK_CHK_GEN_N",         \[bytes] ->
                                      heapStackCheckGen (Just bytes) Nothing ),

  -- A stack check on entry to a thunk, where the argument is the thunk pointer.
  ( fsLit "STK_CHK_NP"   ,         \[node] -> entryHeapCheck' False node 0 [] (return ())),

  ( fsLit "LOAD_THREAD_STATE",     \[] -> emitLoadThreadState ),
  ( fsLit "SAVE_THREAD_STATE",     \[] -> emitSaveThreadState ),

  ( fsLit "LDV_ENTER",             \[e] -> ldvEnter e ),
  ( fsLit "LDV_RECORD_CREATE",     \[e] -> ldvRecordCreate e ),

  ( fsLit "PUSH_UPD_FRAME",        \[sp,e] -> emitPushUpdateFrame sp e ),
  ( fsLit "SET_HDR",               \[ptr,info,ccs] ->
                                        emitSetDynHdr ptr info ccs ),
  ( fsLit "TICK_ALLOC_PRIM",       \[hdr,goods,slop] ->
                                        tickyAllocPrim hdr goods slop ),
  ( fsLit "TICK_ALLOC_PAP",        \[goods,slop] ->
                                        tickyAllocPAP goods slop ),
  ( fsLit "TICK_ALLOC_UP_THK",     \[goods,slop] ->
                                        tickyAllocThunk goods slop ),
  ( fsLit "UPD_BH_UPDATABLE",      \[reg] -> emitBlackHoleCode False reg ),
  ( fsLit "UPD_BH_SINGLE_ENTRY",   \[reg] -> emitBlackHoleCode True  reg )
 ]

emitPushUpdateFrame :: CmmExpr -> CmmExpr -> FCode ()
emitPushUpdateFrame sp e = do
  dflags <- getDynFlags
  emitUpdateFrame dflags sp mkUpdInfoLabel e

pushStackFrame :: [CmmParse CmmExpr] -> CmmParse () -> CmmParse ()
pushStackFrame fields body = do
  dflags <- getDynFlags
  exprs <- sequence fields
  updfr_off <- getUpdFrameOff
  let (new_updfr_off, _, g) = copyOutOflow dflags NativeReturn Ret Old
                                           [] updfr_off exprs
  emit g
  withUpdFrameOff new_updfr_off body

profilingInfo dflags desc_str ty_str
  = if not (gopt Opt_SccProfilingOn dflags)
    then NoProfilingInfo
    else ProfilingInfo (stringToWord8s desc_str)
                       (stringToWord8s ty_str)

staticClosure :: PackageId -> FastString -> FastString -> [CmmLit] -> CmmParse ()
staticClosure pkg cl_label info payload
  = do dflags <- getDynFlags
       let lits = mkStaticClosure dflags (mkCmmInfoLabel pkg info) dontCareCCS payload [] [] []
       code $ emitDataLits (mkCmmDataLabel pkg cl_label) lits

foreignCall
        :: String
        -> [CmmParse (LocalReg, ForeignHint)]
        -> CmmParse CmmExpr
        -> [CmmParse (CmmExpr, ForeignHint)]
        -> Safety
        -> CmmReturnInfo
        -> P (CmmParse ())
foreignCall conv_string results_code expr_code args_code safety ret
  = do  conv <- case conv_string of
          "C" -> return CCallConv
          "stdcall" -> return StdCallConv
          _ -> fail ("unknown calling convention: " ++ conv_string)
        return $ do
          dflags <- getDynFlags
          results <- sequence results_code
          expr <- expr_code
          args <- sequence args_code
          let
                  expr' = adjCallTarget dflags conv expr args
                  (arg_exprs, arg_hints) = unzip args
                  (res_regs,  res_hints) = unzip results
                  fc = ForeignConvention conv arg_hints res_hints ret
                  target = ForeignTarget expr' fc
          _ <- code $ emitForeignCall safety res_regs target arg_exprs
          return ()


doReturn :: [CmmParse CmmExpr] -> CmmParse ()
doReturn exprs_code = do
  dflags <- getDynFlags
  exprs <- sequence exprs_code
  updfr_off <- getUpdFrameOff
  emit (mkReturnSimple dflags exprs updfr_off)

mkReturnSimple  :: DynFlags -> [CmmActual] -> UpdFrameOffset -> CmmAGraph
mkReturnSimple dflags actuals updfr_off =
  mkReturn dflags e actuals updfr_off
  where e = entryCode dflags (CmmLoad (CmmStackSlot Old updfr_off)
                             (gcWord dflags))

doRawJump :: CmmParse CmmExpr -> [GlobalReg] -> CmmParse ()
doRawJump expr_code vols = do
  dflags <- getDynFlags
  expr <- expr_code
  updfr_off <- getUpdFrameOff
  emit (mkRawJump dflags expr updfr_off vols)

doJumpWithStack :: CmmParse CmmExpr -> [CmmParse CmmExpr]
                -> [CmmParse CmmExpr] -> CmmParse ()
doJumpWithStack expr_code stk_code args_code = do
  dflags <- getDynFlags
  expr <- expr_code
  stk_args <- sequence stk_code
  args <- sequence args_code
  updfr_off <- getUpdFrameOff
  emit (mkJumpExtra dflags NativeNodeCall expr args updfr_off stk_args)

doCall :: CmmParse CmmExpr -> [CmmParse LocalReg] -> [CmmParse CmmExpr]
       -> CmmParse ()
doCall expr_code res_code args_code = do
  dflags <- getDynFlags
  expr <- expr_code
  args <- sequence args_code
  ress <- sequence res_code
  updfr_off <- getUpdFrameOff
  c <- code $ mkCall expr (NativeNodeCall,NativeReturn) ress args updfr_off []
  emit c

adjCallTarget :: DynFlags -> CCallConv -> CmmExpr -> [(CmmExpr, ForeignHint) ]
              -> CmmExpr
-- On Windows, we have to add the '@N' suffix to the label when making
-- a call with the stdcall calling convention.
adjCallTarget dflags StdCallConv (CmmLit (CmmLabel lbl)) args
 | platformOS (targetPlatform dflags) == OSMinGW32
  = CmmLit (CmmLabel (addLabelSize lbl (sum (map size args))))
  where size (e, _) = max (wORD_SIZE dflags) (widthInBytes (typeWidth (cmmExprType dflags e)))
                 -- c.f. CgForeignCall.emitForeignCall
adjCallTarget _ _ expr _
  = expr

primCall
        :: [CmmParse (CmmFormal, ForeignHint)]
        -> FastString
        -> [CmmParse CmmExpr]
        -> P (CmmParse ())
primCall results_code name args_code
  = case lookupUFM callishMachOps name of
        Nothing -> fail ("unknown primitive " ++ unpackFS name)
        Just p  -> return $ do
                results <- sequence results_code
                args <- sequence args_code
                code (emitPrimCall (map fst results) p args)

doStore :: CmmType -> CmmParse CmmExpr  -> CmmParse CmmExpr -> CmmParse ()
doStore rep addr_code val_code
  = do dflags <- getDynFlags
       addr <- addr_code
       val <- val_code
        -- if the specified store type does not match the type of the expr
        -- on the rhs, then we insert a coercion that will cause the type
        -- mismatch to be flagged by cmm-lint.  If we don't do this, then
        -- the store will happen at the wrong type, and the error will not
        -- be noticed.
       let val_width = typeWidth (cmmExprType dflags val)
           rep_width = typeWidth rep
       let coerce_val
                | val_width /= rep_width = CmmMachOp (MO_UU_Conv val_width rep_width) [val]
                | otherwise              = val
       emitStore addr coerce_val

-- -----------------------------------------------------------------------------
-- If-then-else and boolean expressions

data BoolExpr
  = BoolExpr `BoolAnd` BoolExpr
  | BoolExpr `BoolOr`  BoolExpr
  | BoolNot BoolExpr
  | BoolTest CmmExpr

-- ToDo: smart constructors which simplify the boolean expression.

cmmIfThenElse cond then_part else_part = do
     then_id <- newBlockId
     join_id <- newBlockId
     c <- cond
     emitCond c then_id
     else_part
     emit (mkBranch join_id)
     emitLabel then_id
     then_part
     -- fall through to join
     emitLabel join_id

cmmRawIf cond then_id = do
    c <- cond
    emitCond c then_id

-- 'emitCond cond true_id'  emits code to test whether the cond is true,
-- branching to true_id if so, and falling through otherwise.
emitCond (BoolTest e) then_id = do
  else_id <- newBlockId
  emit (mkCbranch e then_id else_id)
  emitLabel else_id
emitCond (BoolNot (BoolTest (CmmMachOp op args))) then_id
  | Just op' <- maybeInvertComparison op
  = emitCond (BoolTest (CmmMachOp op' args)) then_id
emitCond (BoolNot e) then_id = do
  else_id <- newBlockId
  emitCond e else_id
  emit (mkBranch then_id)
  emitLabel else_id
emitCond (e1 `BoolOr` e2) then_id = do
  emitCond e1 then_id
  emitCond e2 then_id
emitCond (e1 `BoolAnd` e2) then_id = do
        -- we'd like to invert one of the conditionals here to avoid an
        -- extra branch instruction, but we can't use maybeInvertComparison
        -- here because we can't look too closely at the expression since
        -- we're in a loop.
  and_id <- newBlockId
  else_id <- newBlockId
  emitCond e1 and_id
  emit (mkBranch else_id)
  emitLabel and_id
  emitCond e2 then_id
  emitLabel else_id


-- -----------------------------------------------------------------------------
-- Table jumps

-- We use a simplified form of C-- switch statements for now.  A
-- switch statement always compiles to a table jump.  Each arm can
-- specify a list of values (not ranges), and there can be a single
-- default branch.  The range of the table is given either by the
-- optional range on the switch (eg. switch [0..7] {...}), or by
-- the minimum/maximum values from the branches.

doSwitch :: Maybe (Int,Int) -> CmmParse CmmExpr -> [([Int],Either BlockId (CmmParse ()))]
         -> Maybe (CmmParse ()) -> CmmParse ()
doSwitch mb_range scrut arms deflt
   = do
        -- Compile code for the default branch
        dflt_entry <- 
                case deflt of
                  Nothing -> return Nothing
                  Just e  -> do b <- forkLabelledCode e; return (Just b)

        -- Compile each case branch
        table_entries <- mapM emitArm arms

        -- Construct the table
        let
            all_entries = concat table_entries
            ixs = map fst all_entries
            (min,max) 
                | Just (l,u) <- mb_range = (l,u)
                | otherwise              = (minimum ixs, maximum ixs)

            entries = elems (accumArray (\_ a -> Just a) dflt_entry (min,max)
                                all_entries)
        expr <- scrut
        -- ToDo: check for out of range and jump to default if necessary
        emit (mkSwitch expr entries)
   where
        emitArm :: ([Int],Either BlockId (CmmParse ())) -> CmmParse [(Int,BlockId)]
        emitArm (ints,Left blockid) = return [ (i,blockid) | i <- ints ]
        emitArm (ints,Right code) = do
           blockid <- forkLabelledCode code
           return [ (i,blockid) | i <- ints ]

forkLabelledCode :: CmmParse () -> CmmParse BlockId
forkLabelledCode p = do
  ag <- getCode p
  l <- newBlockId
  emitOutOfLine l ag
  return l

-- -----------------------------------------------------------------------------
-- Putting it all together

-- The initial environment: we define some constants that the compiler
-- knows about here.
initEnv :: DynFlags -> Env
initEnv dflags = listToUFM [
  ( fsLit "SIZEOF_StgHeader",
    VarN (CmmLit (CmmInt (fromIntegral (fixedHdrSize dflags * wORD_SIZE dflags)) (wordWidth dflags)) )),
  ( fsLit "SIZEOF_StgInfoTable",
    VarN (CmmLit (CmmInt (fromIntegral (stdInfoTableSizeB dflags)) (wordWidth dflags)) ))
  ]

parseCmmFile :: DynFlags -> FilePath -> IO (Messages, Maybe CmmGroup)
parseCmmFile dflags filename = do
  showPass dflags "ParseCmm"
  buf <- hGetStringBuffer filename
  let
        init_loc = mkRealSrcLoc (mkFastString filename) 1 1
        init_state = (mkPState dflags buf init_loc) { lex_state = [0] }
                …