M2compiler-V1/M2c.atg

COMPILER M2c
(* Modula-2 program modules without procedures, with an MC64 backend
   (see MGen for details).

   - program module only, no DEFINITION / IMPLEMENTATION split
   - no local modules, no EXPORT, no PRIORITY
   - no ProcedureDeclaration, FormalParameters, ProcedureType,
     ProcedureCall, ActualParameters, FORWARD, RETURN
   - statements: assignment, IF, CASE, WHILE, REPEAT, LOOP/EXIT, FOR, WITH
   - symbol table (SymTab) with static type checking: error codes
     200/201/202 and 210-224, same lenient rules as the reference
     implementation (single pass, declare-before-use; INTEGER,
     CARDINAL and subranges form one integer family; no mixed
     INTEGER/REAL arithmetic; INTEGER assigns to REAL; 1-character
     literal is CHAR; InvalidType suppresses follow-on errors)
   - backend (MGen): emits a single-module MC64 image <ModName>.MCD
     (current directory), runnable with mcint. Lowered: scalar
     globals, CONST literals (startup stores), SET OF ordinals
     (bit masks) with literals, IN, = and #; full scalar
     expressions on the stack machine; control flow via E0/E1 jumps.
     Everything else parses and type-checks but gets error 230
     (not supported in this phase): ARRAY/RECORD/POINTER variables,
     string variables, WITH, non-literal CONST expressions and BY
     steps, EXIT outside LOOP, imported names used as values.
   - test convention (the language has no I/O): a global
       VAR ExitCode : INTEGER;
     is printed as decimal + CRLF through an embedded helper;
     without it the program just ends.
   - known semantic edges: INTEGER DIV/MOD truncate toward zero
     (not Modula-2 floor); CARDINAL values past MAXINT compare as
     signed; AND/OR are eager (no short-circuit); REAL widens to
     binary64; assignment targets cost one dead load. *)

IMPORT SymTab, MGen;

CHARACTERS
  eol      = CHR(13) .
  letter   = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz" .
  digit    = "0123456789" .
  hexDigit = digit + "ABCDEF" .
  noQuote1 = ANY - "'" - eol .
  noQuote2 = ANY - '"' - eol .

IGNORE CHR(9) .. CHR(13)

COMMENTS
  FROM "(*" TO "*)" NESTED

TOKENS
  ident   = letter { letter | digit } .
  integer = digit { digit }
          | digit { digit } CONTEXT("..")
          | digit { hexDigit } "H" .
  real    = digit { digit } "." { digit }
            [ "E" [ "+" | "-" ] digit { digit } ] .
  string  = "'" { noQuote1 } "'"
          | '"' { noQuote2 } '"' .

PRODUCTIONS
  M2c                                   (. VAR m1, m2: SymTab.Name; .)
    = "MODULE"
      GetIdent<m1>                      (. SymTab.Init; MGen.OpenModule(m1);
                                           IF ~SymTab.Enter(m1, SymTab.KindModule)
                                           THEN SemError(200) END .)
      ";"
      { Import } Block GetIdent<m2>     (. IF ~SymTab.Equal(m1, m2)
                                           THEN SemError(202) END .)
      "."                               (. MGen.EndModule;
                                           SymTab.PrintTable; .) .
  Import                                (. VAR n: SymTab.Name; .)
    = "FROM"
      GetIdent<n>                       (. IF ~SymTab.Enter(n, SymTab.KindImport)
                                           THEN SemError(200) END .)
      "IMPORT"
      ImportList ";"
    | "IMPORT"
      ImportList ";" .
  ImportList                            (. VAR n: SymTab.Name; .)
    = GetIdent<n>                       (. IF ~SymTab.Enter(n, SymTab.KindImport)
                                           THEN SemError(200) END .)
      { ","
        GetIdent<n>                     (. IF ~SymTab.Enter(n, SymTab.KindImport)
                                           THEN SemError(200) END .) } .
  Block      = { Declaration }
               [ "BEGIN"                (. MGen.BeginBody; .)
                 StatSeq ]
               "END" .
  Declaration = "CONST"
                          {
                            ConstDecl ";" }
              | "TYPE"
                          {
                            TypeDecl ";" }
              | "VAR"
                          {
                            VarDecl ";" } .
  ConstDecl                             (. VAR n: SymTab.Name;
                                             t: SymTab.TypeIndex;
                                             lx: MGen.LitStr;
                                             cls: INTEGER; .)
    = GetIdent<n>                       (. IF ~SymTab.Enter(n, SymTab.KindConst)
                                           THEN SemError(200) END .)
      "="                               (. MGen.NoEmitEnter; .)
      ConstExpr<t, lx>                  (. SymTab.SetSymType(n, t);
                                           cls := SymTab.ClassOf(t);
                                           IF cls = SymTab.ClStr THEN
                                             SemError(230)
                                           ELSIF ~MGen.IsLit(lx) THEN
                                             SemError(230)
                                           END;
                                           MGen.DeclConst(n, lx, t);
                                           MGen.NoEmitExit; .) .
  ConstExpr <VAR t: SymTab.TypeIndex; VAR lx: MGen.LitStr>
    = Expr<t, lx> .
  TypeDecl                              (. VAR n: SymTab.Name;
                                             t0, t1: SymTab.TypeIndex; .)
    = GetIdent<n>                       (. IF ~SymTab.Enter(n, SymTab.KindType)
                                           THEN SemError(200) END;
                                           t0 := SymTab.NewAlias();
                                           SymTab.SetSymType(n, t0); .)
      "="
      Type<t1>                          (. IF t1 = t0 THEN SemError(223);
                                             SymTab.SetTarget(t0,
                                               SymTab.InvalidType)
                                           ELSE SymTab.SetTarget(t0, t1) END; .) .
  VarDecl                               (. VAR t: SymTab.TypeIndex;
                                             i: CARDINAL;
                                             nm: SymTab.Name;
                                             cls: INTEGER; .)
    = VarIdents ":"
      Type<t>                           (. cls := SymTab.ClassOf(t);
                                           IF (cls # SymTab.ClInt)
                                              & (cls # SymTab.ClReal)
                                              & (cls # SymTab.ClBool)
                                              & (cls # SymTab.ClChar)
                                              & (cls # SymTab.ClEnum)
                                              & (cls # SymTab.ClSet) THEN
                                             SemError(230)
                                           END;
                                           i := 0;
                                           WHILE i < SymTab.PendCount() DO
                                             SymTab.PendName(i, nm);
                                             MGen.DeclVar(nm);
                                             INC(i)
                                           END;
                                           SymTab.FixPending(t); .) .
  VarIdents                             (. VAR n: SymTab.Name; .)
    = GetIdent<n>                       (. IF ~SymTab.EnterPending(n,
                                             SymTab.KindVar)
                                           THEN SemError(200) END .)
      { ","
        GetIdent<n>                     (. IF ~SymTab.EnterPending(n,
                                             SymTab.KindVar)
                                           THEN SemError(200) END .) } .
  QualIdent <VAR t: SymTab.TypeIndex>
                                        (. VAR n, m: SymTab.Name; .)
    = GetIdent<n>                       (. IF ~SymTab.Lookup(n) THEN
                                             SemError(201);
                                             t := SymTab.InvalidType
                                           ELSIF (SymTab.SymKind(n) #
                                                  SymTab.KindType)
                                             & (SymTab.SymKind(n) #
                                                SymTab.KindPredef)
                                             & (SymTab.SymKind(n) #
                                                SymTab.KindImport) THEN
                                             SemError(221);
                                             t := SymTab.InvalidType
                                           ELSE t := SymTab.SymType(n) END; .)
      { "."
        GetIdent<m>                     (. t := SymTab.InvalidType; .) } .

  (* Types: ProcedureType removed; subrange factored for LL(1) *)
  Type <VAR t: SymTab.TypeIndex>
    = SimpleType<t> | ArrayType<t> | RecordType<t>
    | SetType<t> | PointerType<t> .
  SimpleType <VAR t: SymTab.TypeIndex>
                                        (. VAR t1, t2: SymTab.TypeIndex;
                                             lx1, lx2: MGen.LitStr; .)
    = QualIdent<t> [ "["
                      (. MGen.NoEmitEnter; .)
                      ConstExpr<t1, lx1> (. IF (t1 # SymTab.InvalidType)
                                            & (SymTab.ClassOf(t1) #
                                               SymTab.ClInt)
                                            & (SymTab.ClassOf(t1) #
                                               SymTab.ClChar)
                                            & (SymTab.ClassOf(t1) #
                                               SymTab.ClEnum) THEN
                                            SemError(224) END; .)
                      ".."
                      ConstExpr<t2, lx2> (. IF (t2 # SymTab.InvalidType)
                                            & (SymTab.ClassOf(t2) #
                                               SymTab.ClInt)
                                            & (SymTab.ClassOf(t2) #
                                               SymTab.ClChar)
                                            & (SymTab.ClassOf(t2) #
                                               SymTab.ClEnum) THEN
                                            SemError(224) END; .)
                      "]"
                                     (. t := SymTab.NewSub(t1);
                                        MGen.NoEmitExit; .) ]
    | "["                               (. MGen.NoEmitEnter; .)
      ConstExpr<t1, lx1>                (. IF (t1 # SymTab.InvalidType)
                                            & (SymTab.ClassOf(t1) #
                                               SymTab.ClInt)
                                            & (SymTab.ClassOf(t1) #
                                               SymTab.ClChar)
                                            & (SymTab.ClassOf(t1) #
                                               SymTab.ClEnum) THEN
                                            SemError(224) END; .)
      ".."
      ConstExpr<t2, lx2>                (. IF (t2 # SymTab.InvalidType)
                                            & (SymTab.ClassOf(t2) #
                                               SymTab.ClInt)
                                            & (SymTab.ClassOf(t2) #
                                               SymTab.ClChar)
                                            & (SymTab.ClassOf(t2) #
                                               SymTab.ClEnum) THEN
                                            SemError(224) END; .)
      "]"                               (. t := SymTab.NewSub(t1);
                                           MGen.NoEmitExit; .)
    | Enum<t> .
  Enum <VAR t: SymTab.TypeIndex>
                                        (. VAR n: SymTab.Name;
                                             ord: INTEGER; .)
    = "("                               (. t := SymTab.NewEnum();
                                           ord := 0; .)
      GetIdent<n>                       (. IF ~SymTab.Enter(n,
                                             SymTab.KindConst)
                                           THEN SemError(200) END;
                                           SymTab.SetSymType(n, t);
                                           MGen.DeclConstInt(n, ord);
                                           INC(ord); .)
      { ","
        GetIdent<n>                     (. IF ~SymTab.Enter(n,
                                             SymTab.KindConst)
                                           THEN SemError(200) END;
                                           SymTab.SetSymType(n, t);
                                           MGen.DeclConstInt(n, ord);
                                           INC(ord); .) }
      ")" .
  ArrayType <VAR t: SymTab.TypeIndex>
                                        (. VAR s, s2, e: SymTab.TypeIndex; .)
    = "ARRAY"
      SimpleType<s>                     (. IF (s # SymTab.InvalidType)
                                            & (SymTab.ClassOf(s) #
                                               SymTab.ClInt)
                                            & (SymTab.ClassOf(s) #
                                               SymTab.ClChar)
                                            & (SymTab.ClassOf(s) #
                                               SymTab.ClEnum) THEN
                                            SemError(224) END; .)
      { ","
        SimpleType<s2>                  (. IF (s2 # SymTab.InvalidType)
                                            & (SymTab.ClassOf(s2) #
                                               SymTab.ClInt)
                                            & (SymTab.ClassOf(s2) #
                                               SymTab.ClChar)
                                            & (SymTab.ClassOf(s2) #
                                               SymTab.ClEnum) THEN
                                            SemError(224) END; .) }
      "OF"
      Type<e>                           (. t := SymTab.NewArray(e); .) .
  RecordType <VAR t: SymTab.TypeIndex>
    = "RECORD"                          (. t := SymTab.NewRecord(); .)
      FieldSeq<t>
      "END" .
  FieldSeq <rt: SymTab.TypeIndex>
    = Field<rt> { ";"
                  Field<rt> } .
  Field <rt: SymTab.TypeIndex>
                                        (. VAR et: SymTab.TypeIndex; .)
    = [ FieldIdents<rt> ":"
        Type<et>                       (. SymTab.FixPendingF(rt, et); .) ] .
  FieldIdents <rt: SymTab.TypeIndex>
                                        (. VAR n: SymTab.Name; .)
    = GetIdent<n>                       (. IF ~SymTab.FieldPending(rt, n)
                                           THEN SemError(200) END .)
      { ","
        GetIdent<n>                     (. IF ~SymTab.FieldPending(rt, n)
                                           THEN SemError(200) END .) } .
  SetType <VAR t: SymTab.TypeIndex>
                                        (. VAR s: SymTab.TypeIndex; .)
    = "SET"
      "OF"
      SimpleType<s>                     (. IF (s # SymTab.InvalidType)
                                            & (SymTab.ClassOf(s) #
                                               SymTab.ClInt)
                                            & (SymTab.ClassOf(s) #
                                               SymTab.ClChar)
                                            & (SymTab.ClassOf(s) #
                                               SymTab.ClEnum) THEN
                                            SemError(224) END;
                                           t := SymTab.NewSet(s); .) .
  PointerType <VAR t: SymTab.TypeIndex>
                                        (. VAR b: SymTab.TypeIndex; .)
    = "POINTER"
      "TO"
      Type<b>                           (. t := SymTab.NewPtr(b); .) .

  (* Statements: ProcedureCall and RETURN removed *)
  StatSeq    = Stat { ";"
                     Stat } .
  Stat                                  (. VAR lx: INTEGER; .)
    = [ Assign | IfStat | CaseStat | WhileStat
      | RepeatStat | LoopStat | ForStat | WithStat
      | "EXIT"                 (. IF MGen.TopLoop(lx) THEN
                                    MGen.Jmp(lx)
                                  ELSE SemError(230) END; .) ] .
  Assign                                (. VAR dt, et: SymTab.TypeIndex;
                                             dk: INTEGER;
                                             bn: SymTab.Name;
                                             lxe, lxD: MGen.LitStr;
                                             isR, conv: BOOLEAN; .)
    = Design<dt, dk, bn, FALSE, lxD> ":="
      Expr<et, lxe>                     (. IF (dt # SymTab.InvalidType)
                                           & (dk # SymTab.KindVar)
                                           & (dk # SymTab.KindField)
                                           & (dk # SymTab.KindImport) THEN
                                           SemError(210)
                                         ELSIF ~SymTab.Assignable(et, dt) THEN
                                           SemError(210) END;
                                         IF dk = SymTab.KindImport THEN
                                           SemError(230)
                                         END;
                                         isR := (dt # SymTab.InvalidType)
                                                & (SymTab.ClassOf(dt)
                                                   = SymTab.ClReal);
                                         conv := isR
                                                 & SymTab.IsIntFamily(et);
                                         IF dk = SymTab.KindVar THEN
                                           IF conv THEN
                                             MGen.IntToReal;
                                           END;
                                           MGen.StoreVar(bn)
                                         ELSE MGen.Drop
                                         END; .) .
  IfStat                                (. VAR t: SymTab.TypeIndex;
                                             lxC: MGen.LitStr;
                                             elseL, endL: INTEGER;
                                             hasElse: BOOLEAN; .)
    = "IF"
      Expr<t, lxC>                      (. IF ~SymTab.BoolCheck(t) THEN
                                           SemError(214) END;
                                           elseL := MGen.NewLabel();
                                           endL := MGen.NewLabel();
                                           MGen.Jz(elseL);
                                           hasElse := FALSE; .)
      "THEN"
      StatSeq
      { "ELSIF"                         (. MGen.Jmp(endL);
                                           MGen.DefLabel(elseL); .)
        Expr<t, lxC>                    (. IF ~SymTab.BoolCheck(t) THEN
                                           SemError(214) END;
                                           elseL := MGen.NewLabel();
                                           MGen.Jz(elseL); .)
        "THEN"
        StatSeq }
      [ "ELSE"                          (. MGen.Jmp(endL);
                                           MGen.DefLabel(elseL);
                                           hasElse := TRUE; .)
        StatSeq ]
      "END"                             (. IF ~hasElse THEN
                                           MGen.DefLabel(elseL)
                                         END;
                                         MGen.DefLabel(endL); .) .
  CaseStat                              (. VAR st: SymTab.TypeIndex;
                                             lxS: MGen.LitStr;
                                             tmp, endL: INTEGER; .)
    = "CASE"
      Expr<st, lxS>                     (. tmp := MGen.TempGlobal();
                                           MGen.StoreTemp(tmp);
                                           endL := MGen.NewLabel(); .)
      "OF"
      Case<st, tmp, endL> { "|"
                 Case<st, tmp, endL> }
      [ "ELSE"
        StatSeq ]
      "END"                             (. MGen.DefLabel(endL); .) .
  Case <sel: SymTab.TypeIndex; tmp: INTEGER; endL: INTEGER>
                                        (. VAR lB, lN: INTEGER; .)
    = [ LabelList<sel, tmp, lB, lN> ":" (. MGen.DefLabel(lB); .)
        StatSeq                         (. MGen.Jmp(endL);
                                           MGen.DefLabel(lN); .) ] .
  LabelList <sel: SymTab.TypeIndex; tmp: INTEGER;
             VAR lB: INTEGER; VAR lN: INTEGER>
    =                                   (. lB := MGen.NewLabel();
                                           lN := MGen.NewLabel(); .)
      Labels<sel, tmp, lB> { ","
                    Labels<sel, tmp, lB> }
                                        (. MGen.Jmp(lN); .) .
  Labels <sel: SymTab.TypeIndex; tmp: INTEGER; bodyL: INTEGER>
                                        (. VAR t, t2: SymTab.TypeIndex;
                                             lx1, lx2: MGen.LitStr;
                                             ta, tb, chunk: INTEGER;
                                             r, hasRange: BOOLEAN; .)
    = ConstExpr<t, lx1>                 (. IF ~SymTab.EqCheck(t, sel) THEN
                                           SemError(213) END;
                                           r := (SymTab.ClassOf(sel)
                                                 = SymTab.ClReal)
                                                & (SymTab.ClassOf(t)
                                                   = SymTab.ClReal);
                                           ta := MGen.TempGlobal();
                                           MGen.StoreTemp(ta);
                                           hasRange := FALSE; .)
      [ ".."
        ConstExpr<t2, lx2>              (. IF ~SymTab.EqCheck(t2, sel) THEN
                                           SemError(213) END;
                                           tb := MGen.TempGlobal();
                                           MGen.StoreTemp(tb);
                                           hasRange := TRUE; .) ]
                                        (. IF hasRange THEN
                                             MGen.LoadTemp(tmp);
                                             MGen.LoadTemp(ta);
                                             IF r THEN MGen.RealGe
                                             ELSE MGen.IGe END;
                                             MGen.LoadTemp(tmp);
                                             MGen.LoadTemp(tb);
                                             IF r THEN MGen.RealLe
                                             ELSE MGen.ILe END;
                                             MGen.And
                                           ELSE
                                             MGen.LoadTemp(tmp);
                                             MGen.LoadTemp(ta);
                                             IF r THEN MGen.RealEq
                                             ELSE MGen.Eq END
                                           END;
                                           chunk := MGen.NewLabel();
                                           MGen.Jz(chunk);
                                           MGen.Jmp(bodyL);
                                           MGen.DefLabel(chunk); .) .
  WhileStat                             (. VAR t: SymTab.TypeIndex;
                                             lxC: MGen.LitStr;
                                             topL, endL: INTEGER; .)
    = "WHILE"                           (. topL := MGen.NewLabel();
                                           endL := MGen.NewLabel();
                                           MGen.DefLabel(topL); .)
      Expr<t, lxC>                      (. IF ~SymTab.BoolCheck(t) THEN
                                           SemError(214) END;
                                           MGen.Jz(endL); .)
      "DO"
      StatSeq
      "END"                             (. MGen.Jmp(topL);
                                           MGen.DefLabel(endL); .) .
  RepeatStat                            (. VAR t: SymTab.TypeIndex;
                                             lxC: MGen.LitStr;
                                             topL: INTEGER; .)
    = "REPEAT"                          (. topL := MGen.NewLabel();
                                           MGen.DefLabel(topL); .)
      StatSeq
      "UNTIL"
      Expr<t, lxC>                      (. IF ~SymTab.BoolCheck(t) THEN
                                           SemError(214) END;
                                           MGen.Jz(topL); .) .
  LoopStat                              (. VAR topL, exitL: INTEGER; .)
    = "LOOP"                            (. topL := MGen.NewLabel();
                                           exitL := MGen.NewLabel();
                                           MGen.DefLabel(topL);
                                           MGen.PushLoop(exitL); .)
      StatSeq
      "END"                             (. MGen.Jmp(topL);
                                           MGen.DefLabel(exitL);
                                           MGen.PopLoop; .) .
  ForStat                               (. VAR n, lv: SymTab.Name;
                                             lo, hi: SymTab.TypeIndex;
                                             lxLo, lxHi: MGen.LitStr;
                                             byV, ht: INTEGER;
                                             lTop, lChk, lEnd: INTEGER;
                                             neg: BOOLEAN; .)
    = "FOR"
      GetIdent<n>                       (. IF ~SymTab.Lookup(n) THEN
                                            SemError(201)
                                          ELSIF (SymTab.SymKind(n) #
                                                 SymTab.KindVar)
                                            & (SymTab.SymKind(n) #
                                               SymTab.KindField) THEN
                                            SemError(220)
                                          ELSIF (SymTab.SymType(n) #
                                                 SymTab.InvalidType)
                                            & ~SymTab.IsIntFamily(
                                                SymTab.SymType(n)) THEN
                                            SemError(220) END;
                                            MGen.CopyName(n, lv); .)
      ":="
      Expr<lo, lxLo>                    (. IF (lo # SymTab.InvalidType)
                                           & ~SymTab.IsIntFamily(lo) THEN
                                           SemError(220) END;
                                           MGen.StoreVar(lv); .)
      "TO"
      Expr<hi, lxHi>                    (. IF (hi # SymTab.InvalidType)
                                           & ~SymTab.IsIntFamily(hi) THEN
                                           SemError(220) END;
                                           ht := MGen.TempGlobal();
                                           MGen.StoreTemp(ht);
                                           byV := 1; neg := FALSE; .)
      [ "BY"
        ByLit<byV>                      (. neg := byV < 0; .) ]
      "DO"                              (. lTop := MGen.NewLabel();
                                           lChk := MGen.NewLabel();
                                           lEnd := MGen.NewLabel();
                                           MGen.Jmp(lChk);
                                           MGen.DefLabel(lTop); .)
      StatSeq
      "END"                             (. MGen.LoadVar(lv);
                                           MGen.PushInt(byV);
                                           MGen.Add;
                                           MGen.StoreVar(lv);
                                           MGen.DefLabel(lChk);
                                           MGen.LoadVar(lv);
                                           MGen.LoadTemp(ht);
                                           IF neg THEN MGen.IGe
                                           ELSE MGen.ILe END;
                                           MGen.Jz(lEnd);
                                           MGen.Jmp(lTop);
                                           MGen.DefLabel(lEnd); .) .
  ByLit <VAR v: INTEGER>                (. VAR s: ARRAY [0 .. 255] OF CHAR; .)
    = integer                           (. LexString(s);
                                           IF ~MGen.ParseInt(s, v) THEN
                                             v := 1
                                           END; .)
    | "-" integer                       (. LexString(s);
                                           IF MGen.ParseInt(s, v) THEN
                                             v := -v
                                           ELSE v := -1
                                           END; .) .
  WithStat                              (. VAR dt: SymTab.TypeIndex;
                                             dk: INTEGER;
                                             bnW: SymTab.Name;
                                             lxW: MGen.LitStr;
                                             pushed: BOOLEAN; .)
    = "WITH"
      Design<dt, dk, bnW, FALSE, lxW>   (. pushed := FALSE;
                                           IF dt # SymTab.InvalidType THEN
                                             pushed :=
                                               SymTab.PushRecord(dt);
                                             IF ~pushed THEN
                                               SemError(215)
                                             END
                                           END;
                                           IF pushed THEN
                                             MGen.NoSupEnter;
                                             SemError(230)
                                           END; .)
      "DO"
      StatSeq
      "END"                             (. IF pushed THEN
                                             SymTab.PopScope;
                                             MGen.NoSupExit
                                           END; .) .

  (* Expressions: Designator without ActualParameters.
     Only record fields resolve qualified access; WITH pushes an
     inner scope so field names also work unqualified in its body.
     Each expression synthesizes its SymTab type in t and, for
     single literals, the source text in lx ("" otherwise, used for
     CONST validation). Values travel on the MC64 stack. *)
  Design <VAR t: SymTab.TypeIndex; VAR k: INTEGER;
          VAR bn: SymTab.Name; doLoad: BOOLEAN; VAR lx: MGen.LitStr>
                                        (. VAR n, m: SymTab.Name;
                                             it: SymTab.TypeIndex;
                                             lxI: MGen.LitStr;
                                             cls: INTEGER; .)
    = GetIdent<n>                       (. MGen.CopyName(n, bn);
                                           lx[0] := 0C;
                                           IF ~SymTab.Lookup(n) THEN
                                             SemError(201);
                                             t := SymTab.InvalidType; k := -1;
                                             IF doLoad THEN
                                               MGen.PushInt(0)
                                             END
                                           ELSE
                                             t := SymTab.SymType(n);
                                             k := SymTab.SymKind(n);
                                             IF k = SymTab.KindConst THEN
                                               IF SymTab.Equal(n, "TRUE") THEN
                                                 t := SymTab.BoolType();
                                                 MGen.CopyName("TRUE", lx);
                                                 IF doLoad THEN
                                                   MGen.PushInt(1)
                                                 END
                                               ELSIF SymTab.Equal(n,
                                                       "FALSE") THEN
                                                 t := SymTab.BoolType();
                                                 MGen.CopyName("FALSE", lx);
                                                 IF doLoad THEN
                                                   MGen.PushInt(0)
                                                 END
                                               ELSE
                                                 cls :=
                                                   SymTab.ClassOf(t);
                                                 IF (t #
                                                     SymTab.InvalidType)
                                                    & (cls # SymTab.ClStr)
                                                    & ((cls = SymTab.ClInt)
                                                    OR (cls = SymTab.ClReal)
                                                    OR (cls = SymTab.ClBool)
                                                    OR (cls = SymTab.ClChar)
                                                    OR (cls
                                                        = SymTab.ClEnum)) THEN
                                                   IF doLoad THEN
                                                     MGen.LoadVar(n)
                                                   END
                                                 ELSIF doLoad THEN
                                                   MGen.PushInt(0)
                                                 END
                                               END
                                             ELSIF k = SymTab.KindVar THEN
                                               cls := SymTab.ClassOf(t);
                                               IF (cls = SymTab.ClInt)
                                                  OR (cls = SymTab.ClReal)
                                                  OR (cls = SymTab.ClBool)
                                                  OR (cls = SymTab.ClChar)
                                                  OR (cls
                                                      = SymTab.ClEnum)
                                                  OR (cls
                                                      = SymTab.ClSet) THEN
                                                 IF doLoad THEN
                                                   MGen.LoadVar(n)
                                                 END
                                               ELSE SemError(230);
                                                 IF doLoad THEN
                                                   MGen.PushInt(0)
                                                 END
                                               END
                                             ELSE
                                               IF doLoad THEN
                                                 MGen.PushInt(0)
                                               END;
                                               IF k = SymTab.KindField THEN
                                                 IF ~MGen.NoSup() THEN
                                                   SemError(230)
                                                 END
                                               ELSIF k
                                                     = SymTab.KindImport THEN
                                                 SemError(230)
                                               END
                                             END
                                           END; .)
      { "."                             (. lx[0] := 0C; .)
        GetIdent<m>                     (. IF t = SymTab.InvalidType THEN
                                           ELSIF SymTab.ClassOf(t) #
                                                 SymTab.ClRecord THEN
                                             SemError(215);
                                             t := SymTab.InvalidType
                                           ELSIF ~SymTab.FieldExists(t, m) THEN
                                             SemError(216);
                                             t := SymTab.InvalidType
                                           ELSE t := SymTab.FieldType(t, m);
                                             SemError(230)
                                           END;
                                           IF doLoad THEN
                                             MGen.Drop; MGen.PushInt(0)
                                           END; .)
      | "["
        Expr<it, lxI>                   (. MGen.Drop;
                                           IF t = SymTab.InvalidType THEN
                                           ELSIF SymTab.ClassOf(t) #
                                                 SymTab.ClArray THEN
                                             SemError(217);
                                             t := SymTab.InvalidType
                                           ELSIF (it #
                                                  SymTab.InvalidType)
                                             & ~SymTab.IsIntFamily(it) THEN
                                             SemError(218);
                                             t := SymTab.InvalidType
                                           ELSE t :=
                                             SymTab.ArrayElem(t);
                                             SemError(230)
                                           END;
                                           IF doLoad THEN
                                             MGen.Drop; MGen.PushInt(0)
                                           END; .)
        { ","
          Expr<it, lxI>                 (. MGen.Drop;
                                           IF (it # SymTab.InvalidType)
                                           & ~SymTab.IsIntFamily(it) THEN
                                           SemError(218) END; .) }
        "]"
      | "^"                             (. lx[0] := 0C;
                                           IF t = SymTab.InvalidType THEN
                                           ELSIF SymTab.ClassOf(t) #
                                                 SymTab.ClPtr THEN
                                             SemError(219);
                                             t := SymTab.InvalidType
                                           ELSE t := SymTab.PtrBase(t);
                                             SemError(230)
                                           END;
                                           IF doLoad THEN
                                             MGen.Drop; MGen.PushInt(0)
                                           END; .) } .
  Expr <VAR t: SymTab.TypeIndex; VAR lx: MGen.LitStr>
                                        (. VAR t2: SymTab.TypeIndex;
                                             tc, op: INTEGER;
                                             lx2: MGen.LitStr;
                                             r: BOOLEAN; .)
    = SimExpr<t, lx> [ Rel<op> SimExpr<t2, lx2>
      (. lx[0] := 0C;
         IF op = SymTab.OpIn THEN
           IF SymTab.InCheck(t, t2) THEN
             t := SymTab.BoolType();
             MGen.BitIn
           ELSE SemError(222);
             t := SymTab.InvalidType;
             MGen.Drop; MGen.Drop; MGen.PushInt(0)
           END
         ELSE
           tc := SymTab.ClassOf(t);
           IF SymTab.RelCheck(t, t2, op) THEN
             t := SymTab.BoolType()
           ELSE SemError(213); t := SymTab.InvalidType END;
           IF t # SymTab.InvalidType THEN
             r := tc = SymTab.ClReal;
             IF r THEN
               IF op = SymTab.OpEq THEN MGen.RealEq
               ELSIF (op = SymTab.OpNeq1)
                     OR (op = SymTab.OpNeq2) THEN MGen.RealNe
               ELSIF op = SymTab.OpLt THEN MGen.RealLt
               ELSIF op = SymTab.OpLe THEN MGen.RealLe
               ELSIF op = SymTab.OpGt THEN MGen.RealGt
               ELSE MGen.RealGe END
             ELSE
               IF op = SymTab.OpEq THEN MGen.Eq
               ELSIF (op = SymTab.OpNeq1)
                     OR (op = SymTab.OpNeq2) THEN MGen.Neq
               ELSIF op = SymTab.OpLt THEN MGen.ILt
               ELSIF op = SymTab.OpLe THEN MGen.ILe
               ELSIF op = SymTab.OpGt THEN MGen.IGt
               ELSE MGen.IGe END
             END
           ELSE MGen.Drop; MGen.Drop; MGen.PushInt(0)
           END
         END; .) ] .
  Rel <VAR op: INTEGER>
    = "="                     (. op := SymTab.OpEq; .)
    | "#"                     (. op := SymTab.OpNeq1; .)
    | "<>"                    (. op := SymTab.OpNeq2; .)
    | "<"                     (. op := SymTab.OpLt; .)
    | "<="                    (. op := SymTab.OpLe; .)
    | ">"                     (. op := SymTab.OpGt; .)
    | ">="                    (. op := SymTab.OpGe; .)
    | "IN"                    (. op := SymTab.OpIn; .) .
  SimExpr <VAR t: SymTab.TypeIndex; VAR lx: MGen.LitStr>
                                        (. VAR t2, res2: SymTab.TypeIndex;
                                             op: INTEGER;
                                             lx2: MGen.LitStr;
                                             neg, isR: BOOLEAN; .)
    =                                   (. neg := FALSE; .)
      [ "+" | "-"                       (. neg := TRUE; .) ]
      Term<t, lx>                       (. IF neg THEN
                                           IF MGen.IsLit(lx) THEN
                                             MGen.NegFold(lx, lx)
                                           ELSE lx[0] := 0C
                                           END;
                                           IF SymTab.ClassOf(t)
                                              = SymTab.ClReal THEN
                                             MGen.NegReal
                                           ELSE MGen.NegInt
                                           END
                                         END; .)
      { AddOp<op> Term<t2, lx2>
      (. lx[0] := 0C;
         IF op = SymTab.OpOr THEN
           IF SymTab.BoolCheck(t) & SymTab.BoolCheck(t2) THEN
             t := SymTab.BoolType()
           ELSE SemError(212); t := SymTab.InvalidType END;
           MGen.Or
         ELSE
           IF SymTab.ArithCheck(t, t2, FALSE, res2) THEN t := res2
           ELSE SemError(211); t := SymTab.InvalidType END;
           isR := (t # SymTab.InvalidType)
                  & (SymTab.ClassOf(t) = SymTab.ClReal);
           IF op = SymTab.OpAdd THEN
             IF isR THEN MGen.RealAdd ELSE MGen.Add END
           ELSE
             IF isR THEN MGen.RealSub ELSE MGen.Sub END
           END
         END; .) } .
  AddOp <VAR op: INTEGER>
    = "+"                     (. op := SymTab.OpAdd; .)
    | "-"                     (. op := SymTab.OpSub; .)
    | "OR"                    (. op := SymTab.OpOr; .) .
  Term <VAR t: SymTab.TypeIndex; VAR lx: MGen.LitStr>
                                        (. VAR t2, res2: SymTab.TypeIndex;
                                             op: INTEGER;
                                             lx2: MGen.LitStr;
                                             isR: BOOLEAN;
                                             mt: INTEGER; .)
    = Fact<t, lx> { MulOp<op> Fact<t2, lx2>
      (. lx[0] := 0C;
         IF op = SymTab.OpAnd THEN
           IF SymTab.BoolCheck(t) & SymTab.BoolCheck(t2) THEN
             t := SymTab.BoolType()
           ELSE SemError(212); t := SymTab.InvalidType END;
           MGen.And
         ELSE
           IF SymTab.ArithCheck(t, t2,
                (op = SymTab.OpDiv) OR (op = SymTab.OpMod),
                res2) THEN t := res2
           ELSE SemError(211); t := SymTab.InvalidType END;
           isR := (t # SymTab.InvalidType)
                  & (SymTab.ClassOf(t) = SymTab.ClReal);
           IF op = SymTab.OpTimes THEN
             IF isR THEN MGen.RealMul ELSE MGen.MulU END
           ELSIF op = SymTab.OpSlash THEN
             IF isR THEN MGen.RealDiv ELSE MGen.DivI END
           ELSIF op = SymTab.OpDiv THEN
             MGen.DivI
           ELSE
             mt := MGen.TempGlobal();
             MGen.ModI(mt)
           END
         END; .) } .
  MulOp <VAR op: INTEGER>
    = "*"                     (. op := SymTab.OpTimes; .)
    | "/"                     (. op := SymTab.OpSlash; .)
    | "DIV"                   (. op := SymTab.OpDiv; .)
    | "MOD"                   (. op := SymTab.OpMod; .)
    | "AND"                   (. op := SymTab.OpAnd; .)
    | "&"                     (. op := SymTab.OpAnd; .) .
  Fact <VAR t: SymTab.TypeIndex; VAR lx: MGen.LitStr>
                                        (. VAR s: ARRAY [0 .. 255] OF CHAR;
                                             t2, et, dt, st: SymTab.TypeIndex;
                                             dk: INTEGER;
                                             bnF: SymTab.Name;
                                             lxD, lx2: MGen.LitStr;
                                             v: INTEGER;
                                             c: CARDINAL;
                                             b: LONGCARD; .)
    = integer                         (. LexString(s);
                                         MGen.CopyName(s, lx);
                                         IF MGen.ParseInt(s, v) THEN
                                           MGen.PushInt(v)
                                         ELSIF MGen.ParseCard(s, c) THEN
                                           MGen.PushBits(
                                             VAL(LONGCARD, c))
                                         ELSE MGen.PushInt(0)
                                         END;
                                         t := SymTab.IntType(); .)
    | real                            (. LexString(s);
                                         MGen.CopyName(s, lx);
                                         IF MGen.ParseReal(s, b) THEN
                                           MGen.PushBits(b)
                                         ELSE MGen.PushBits(0H)
                                         END;
                                         t := SymTab.RealType(); .)
    | string                          (. LexString(s);
                                         IF SymTab.StrLen(s) <= 3 THEN
                                           t := SymTab.CharType();
                                           MGen.CopyName(s, lx);
                                           MGen.PushInt(
                                             MGen.CharOrd(s))
                                         ELSE t := SymTab.NewStr();
                                           SemError(230);
                                           lx[0] := 0C;
                                           MGen.PushInt(0)
                                         END; .)
    | Design<dt, dk, bnF, TRUE, lxD>   (. t := dt;
                                         MGen.CopyName(lxD, lx); .)
    | "("
      Expr<et, lx> ")"                (. t := et; .)
    | ( "NOT" | "~" )
      Fact<t2, lx2>                   (. lx[0] := 0C;
                                         IF SymTab.BoolCheck(t2) THEN
                                           t := SymTab.BoolType()
                                         ELSE SemError(212);
                                           t := SymTab.InvalidType END;
                                         MGen.Not; .)
    | SetLit<st>                      (. lx[0] := 0C;
                                         t := st; .) .
  SetLit <VAR t: SymTab.TypeIndex>
                                        (. VAR first, et: SymTab.TypeIndex;
                                             lxE, lxE2: MGen.LitStr;
                                             hasR: BOOLEAN; .)
    = "{"
                                (. MGen.PushInt(0);
                                   t := SymTab.SetFor(SymTab.IntType()); .)
      [ Elem<et, lxE, lxE2, hasR>   (. first := et;
                                       t := SymTab.SetFor(et);
                                       IF hasR THEN MGen.FieldMask
                                       ELSE MGen.Power2 END;
                                       MGen.Or; .)
        { ","
          Elem<et, lxE, lxE2, hasR> (. IF ~SymTab.SetElemCheck(first, et) THEN
                                       SemError(222) END;
                                       IF hasR THEN MGen.FieldMask
                                       ELSE MGen.Power2 END;
                                       MGen.Or; .) } ]
      "}" .
  Elem <VAR t: SymTab.TypeIndex; VAR lx: MGen.LitStr;
        VAR lx2: MGen.LitStr; VAR hasR: BOOLEAN>
                                        (. VAR t2: SymTab.TypeIndex; .)
    = Expr<t, lx>                       (. hasR := FALSE;
                                           lx2[0] := 0C; .)
      [ ".."
        Expr<t2, lx2>                   (. IF ~SymTab.SetElemCheck(t, t2) THEN
                                           SemError(222) END;
                                           hasR := TRUE; .) ] .

  GetIdent <VAR n: SymTab.Name>
    = ident                           (. LexName(n); .) .

END M2c.