File: SubtractExpr.m3 Last modified on Fri Feb 24 11:45:21 PST 1995 by kalsow modified on Thu Nov 29 23:25:28 1990 by muller

MODULE SubtractExpr;

IMPORT CG, Expr, ExprRep, Type, Error, LInt, Int, Reel, EnumType;
IMPORT SetType, Addr, Module, AddressExpr, Target, EnumExpr;
IMPORT IntegerExpr, ReelExpr, SetExpr, LReel, EReel, TInt, ErrType;

TYPE
  Class = { cINT, cLINT, cREAL, cLONG, cEXTND, cADDR, cSET, cENUM };

CONST
  FPType = ARRAY [Class.cREAL .. Class.cEXTND] OF CG.Type {
             CG.Type.Reel,  CG.Type.LReel, CG.Type.XReel };

TYPE
  P = ExprRep.Tab BRANDED "SubtractExpr.P" OBJECT
        extended : BOOLEAN; (* => can subtract enum values *)
        class    : Class;
        tmp      : CG.Var;
      OVERRIDES
        typeOf       := TypeOf;
        check        := Check;
        need_addr    := ExprRep.NotAddressable;
        prep         := Prep;
        compile      := Compile;
        prepLV       := ExprRep.NotLValue;
        compileLV    := ExprRep.NotLValue;
        prepBR       := ExprRep.PrepNoBranch;
        compileBR    := ExprRep.NoBranch;
        evaluate     := Fold;
        isEqual      := ExprRep.EqCheckAB;
        getBounds    := GetBounds;
        isWritable   := ExprRep.IsNever;
        isDesignator := ExprRep.IsNever;
        isZeroes     := ExprRep.IsNever;
        genFPLiteral := ExprRep.NoFPLiteral;
        prepLiteral  := ExprRep.NoPrepLiteral;
        genLiteral   := ExprRep.NoLiteral;
        note_write   := ExprRep.NotWritable;
      END;

PROCEDURE New (a, b: Expr.T; extended := FALSE): Expr.T =
  VAR p: P;
  BEGIN
    p := NEW (P);
    ExprRep.Init (p);
    p.a := a;
    p.b := b;
    p.extended := extended;
    p.tmp := NIL;
    RETURN p;
  END New;

PROCEDURE TypeOf (p: P): Type.T =
  VAR ta: Type.T;
  BEGIN
    ta := Type.Base (Expr.TypeOf (p.a));
    IF (p.extended) THEN
      ta := Int.T;
    ELSIF Type.IsSubtype (ta, Addr.T) AND
      Type.IsSubtype (Type.Base (Expr.TypeOf (p.b)), Addr.T) THEN
      ta := Int.T;
    END;
    RETURN ta;
  END TypeOf;

PROCEDURE Check (p: P;  VAR cs: Expr.CheckState) =
  VAR ta, tb, range: Type.T;
  BEGIN
    Expr.TypeCheck (p.a, cs);
    Expr.TypeCheck (p.b, cs);
    ta := Type.Base (Expr.TypeOf (p.a));
    tb := Type.Base (Expr.TypeOf (p.b));
    IF    (ta = Int.T)   AND (tb = Int.T)   THEN
      p.class := Class.cINT;
    ELSIF (ta = LInt.T)  AND (tb = LInt.T)  THEN
      p.class := Class.cLINT;
    ELSIF (ta = Reel.T)  AND (tb = Reel.T)  THEN
      p.class := Class.cREAL;
    ELSIF (ta = LReel.T) AND (tb = LReel.T) THEN
      p.class := Class.cLONG;
    ELSIF (ta = EReel.T) AND (tb = EReel.T) THEN
      p.class := Class.cEXTND;
    ELSIF (ta = ErrType.T) OR (tb = ErrType.T) THEN
      p.class := Class.cINT; (* there's already an error *)
      ta := ErrType.T;
    ELSIF SetType.Split (ta, range) THEN
      p.class := Class.cSET;
      IF NOT Type.IsEqual (ta, tb, NIL) THEN
        ta := Expr.BadOperands ("\'-\'", ta, tb);
      END;
    ELSIF EnumType.Is (ta) THEN
      p.class := Class.cENUM;
      IF (p.extended) AND (tb = Int.T)
        THEN ta := Int.T;
        ELSE ta := Expr.BadOperands ("\'-\'", ta, tb);
      END;
    ELSIF Type.IsSubtype (ta, Addr.T) THEN
      p.class := Class.cADDR;
      IF    (tb = Int.T)                THEN ta := Addr.T;
      ELSIF Type.IsSubtype (tb, Addr.T) THEN ta := Int.T;
      ELSE  ta := Expr.BadOperands ("\'-\'", ta, tb);
      END;
      IF Module.IsSafe () THEN Error.Msg ("unsafe \'-\'") END;
    ELSE
      ta := Expr.BadOperands ("\'-\'", ta, tb);
      p.class := Class.cINT;
    END;
    p.type := ta;
  END Check;

PROCEDURE Prep (p: P) =
  VAR info: Type.Info;
  BEGIN
    Expr.Prep (p.a);
    Expr.Prep (p.b);
    IF (p.class = Class.cSET) THEN
      EVAL Type.CheckInfo (p.type, info);
      IF (info.size > Target.Integer.size) THEN
        p.tmp := CG.Declare_temp (info.size, Target.Integer.align,
                                  CG.Type.Struct, in_memory := TRUE);
        CG.Load_addr_of (p.tmp, 0, Target.Integer.align);
        CG.Force ();
        Expr.Compile (p.a);
        Expr.Compile (p.b);
        CG.Set_difference (info.size);
      END;
    END;
  END Prep;

PROCEDURE Compile (p: P) =
  VAR size: INTEGER;  info: Type.Info;
  BEGIN
    CASE p.class OF
    | Class.cINT, Class.cENUM =>
        Expr.Compile (p.a);
        Expr.Compile (p.b);
        CG.Subtract (Target.Integer.cg_type);
    | Class.cLINT =>
        Expr.Compile (p.a);
        Expr.Compile (p.b);
        CG.Subtract (Target.Longint.cg_type);
    | Class.cREAL, Class.cLONG, Class.cEXTND =>
        Expr.Compile (p.a);
        Expr.Compile (p.b);
        CG.Subtract (FPType [p.class]);
    | Class.cSET  =>
        EVAL Type.CheckInfo (p.type, info);
        size := info.size;
        IF (size > Target.Integer.size) THEN
          (* Prep did most of the work *)
          CG.Load_addr_of_temp (p.tmp, 0, Target.Integer.align);
          p.tmp := NIL;
        ELSE
          Expr.Compile (p.a);
          Expr.Compile (p.b);
          CG.Set_difference (size);
        END;
    | Class.cADDR =>
        IF (p.type = Addr.T) THEN (* Addr - Int *)
          Expr.Compile (p.a);
          Expr.Compile (p.b);
          CG.Index_bytes (-Target.Byte);
        ELSE (* Addr - Addr *)
          Expr.Compile (p.a);
          CG.Loophole (CG.Type.Addr, Target.Word.cg_type);
          Expr.Compile (p.b);
          CG.Loophole (CG.Type.Addr, Target.Word.cg_type);
          CG.Subtract (Target.Word.cg_type);
        END;
    END;
  END Compile;

PROCEDURE Fold (p: P): Expr.T =
  VAR e1, e2, e3: Expr.T;  x1, x2, x3: Target.Int;  t1: Type.T;
  BEGIN
    e1 := Expr.ConstValue (p.a);
    e2 := Expr.ConstValue (p.b);
    e3 := NIL;
    IF    (e1 = NIL) OR (e2 = NIL)          THEN
    ELSIF IntegerExpr.Subtract (e1, e2, e3) THEN
    ELSIF (p.extended)
      AND EnumExpr.Split (e1, x1, t1)
      AND IntegerExpr.Split (e2, x2, t1)
      AND TInt.Subtract (x1, x2, x3) THEN
      e3 := IntegerExpr.New (t1, x3);
    ELSIF ReelExpr.Subtract    (e1, e2, e3) THEN
    ELSIF AddressExpr.Subtract (e1, e2, e3) THEN
    ELSIF SetExpr.Difference   (e1, e2, e3) THEN
    END;
    RETURN e3;
  END Fold;

PROCEDURE GetBounds (p: P;  VAR min, max: Target.Int) =
  VAR min_a, max_a, min_b, max_b, diff: Target.Int;
  BEGIN
    EVAL Type.GetBounds (p.type, min, max);
    Expr.GetBounds (p.a, min_a, max_a);
    Expr.GetBounds (p.b, min_b, max_b);
    IF TInt.Subtract (min_a, max_b, diff) AND TInt.LT (min, diff) THEN
      min := diff;
    END;
    IF TInt.Subtract (max_a, min_b, diff) AND TInt.LT (diff, max) THEN
      max := diff;
    END;
  END GetBounds;

BEGIN
END SubtractExpr.