Copyright (C) 1994, Digital Equipment Corp.File: DivExpr.m3
MODULE; IMPORT CG, Expr, ExprRep, Type, Int, IntegerExpr, TInt, Target; TYPE P = ExprRep.Tab BRANDED "DivExpr.P" OBJECT OVERRIDES typeOf := ExprRep.NoType; check := Check; need_addr := ExprRep.NotAddressable; prep := Prep; compile := Compile; prepLV := ExprRep.NotLValue; compileLV := ExprRep.NotLValue; prepBR := ExprRep.NotBoolean; compileBR := ExprRep.NotBoolean; evaluate := Fold; isEqual := ExprRep.EqCheckAB; getBounds := ExprRep.NoBounds; isWritable := ExprRep.IsNever; isDesignator := ExprRep.IsNever; isZeroes := ExprRep.IsNever; genFPLiteral := ExprRep.NoFPLiteral; prepLiteral := ExprRep.NoPrepLiteral; genLiteral := ExprRep.NoLiteral; note_write := ExprRep.NotWritable; END; PROCEDURE DivExpr New (a, b: Expr.T): Expr.T = VAR p: P; BEGIN p := NEW (P); ExprRep.Init (p); p.a := a; p.b := b; p.type := Int.T; RETURN p; END New; PROCEDURECheck (p: P; VAR cs: Expr.CheckState) = VAR ta, tb: Type.T; BEGIN INC (cs.div_ops); 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) OR (tb # Int.T) THEN p.type := Expr.BadOperands ("DIV", ta, tb); END; END Check; PROCEDUREPrep (p: P) = BEGIN Expr.Prep (p.a); Expr.Prep (p.b); END Prep; PROCEDURECompile (p: P) = VAR e1, e2, e3: Expr.T; divisor: Target.Int; log: INTEGER; BEGIN e1 := Expr.ConstValue (p.a); e2 := Expr.ConstValue (p.b); e3 := NIL; IF (e1 # NIL) AND (e2 # NIL) AND IntegerExpr.Div (e1, e2, e3) THEN Expr.Compile (e3); ELSIF (e2 # NIL) AND IntegerExpr.Split (e2, divisor) AND SmallPowerOfTwo (divisor, log) THEN IF (e1 = NIL) THEN e1 := p.a; END; IF (log = 0) THEN (* divide by one *) Expr.Compile (e1); ELSE Expr.Compile (e1); CG.Extract_mn (TRUE, log, Target.Integer.size - log); END; ELSE IF (e1 = NIL) THEN e1 := p.a; END; IF (e2 = NIL) THEN e2 := p.b; END; Expr.Compile (e1); Expr.Compile (e2); CG.Div (CG.Type.Int, Expr.GetSign (e1), Expr.GetSign (e2)); END; END Compile; PROCEDUREFold (p: P): Expr.T = VAR e1, e2, e3: Expr.T; BEGIN e1 := Expr.ConstValue (p.a); e2 := Expr.ConstValue (p.b); e3 := NIL; IF IntegerExpr.Div (e1, e2, e3) THEN END; RETURN e3; END Fold; VAR(*CONST*) powers : ARRAY [0..63] OF Target.Int; max_power := 0; PROCEDURESmallPowerOfTwo (READONLY x: Target.Int; VAR log: INTEGER): BOOLEAN= VAR lo, hi, mid: INTEGER; BEGIN IF max_power <= 0 THEN powers[0] := TInt.One; FOR i := 1 TO MIN (Target.Integer.size - 2, LAST (powers)) DO IF TInt.Add (powers[i-1], powers[i-1], powers[i]) THEN max_power := i; END; END; END; lo := 0; hi := max_power+1; WHILE (lo < hi) DO mid := (lo + hi) DIV 2; IF TInt.EQ (x, powers[mid]) THEN log := mid; RETURN TRUE; ELSIF TInt.LT (x, powers[mid]) THEN hi := mid; ELSE lo := mid + 1; END; END; log := -1; RETURN FALSE; END SmallPowerOfTwo; BEGIN END DivExpr.