[Oberon] PO2013 compiler and SET operations

[Jörg]

Hi all

 

I think ORG.Set*(VAR x, y: Item) is the culprit.

 

Currently, in the end it is

     IF x.mode = ORB.Const THEN

        IF x.a # 0 THEN Put1(Xor, y.r, y.r, -1); Put1a(And, RH-1, y.r, x.a) END ;

        x.mode := Reg; x.r := RH-1

      ELSE DEC(RH); Put0(Ann, RH-1, x.r, y.r)

      END

 

But is should be

     IF x.mode = ORB.Const THEN

        IF x.a # 0 THEN Put1(Xor, y.r, y.r, -1); Put1a(And, RH-1, y.r, x.a) END ;

        x.mode := Reg;

      ELSE DEC(RH); Put0(Ann, RH-1, x.r, y.r)

      END;

      x.r := RH-1

 

br

Jörg

 

Am 29.07.20, 18:03 schrieb "Oberon im Auftrag von Hellwig Geisse" <oberon-bounces at lists.inf.ethz.ch im Auftrag von hellwig.geisse at mni.thm.de>:

 

    Michael,

 

    On Mi, 2020-07-29 at 17:08 +0200, Michael Schierl wrote:

    > 

    >   PROCEDURE SetDiff(a, b:SET): SET;

    >   BEGIN

    >   RETURN a - b

    >   END SetDiff;

    > 

    >   PROCEDURE Mask1(a, b: INTEGER): INTEGER;

    >   BEGIN

    >   RETURN SYSTEM.VAL(INTEGER, SetDiff(SYSTEM.VAL(SET, a), {b .. b + 7}))

    >   END Mask1;

    > 

    >   PROCEDURE Mask2(a, b: INTEGER): INTEGER;

    >   BEGIN

    >   RETURN SYSTEM.VAL(INTEGER, SYSTEM.VAL(SET, a) - {b .. b + 7})

    >   END Mask2;

    > 

 

    this seems to be an erroneous translation of the set difference

    operator, as far as I can see. This operator essentially gets

    compiled to an "and negated" (ANN) instruction. The instruction

    sequence for SetDiff is correct, it ends with "ANN R0,R0,R1"

    (result in R0, a in R0, b in R1). But the instruction sequence

    for Mask2 ends with "ANN R0,R1,R1", which yields 0 in R0

    independent of the value in R1. The correct sequence should be

    "ANN R0,R1,R0". I explored this with Andreas' Extended Oberon

    compiler.

 

    Hellwig

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