Nachteile von Abstraktem Maschinen-Code

Oberon Source-Code

VAR

ch: CHAR;


lint: LONGINT;

BEGIN

lint := LONGWORD(ORD(ch));

LOAD1
ORD
LONG
STRORE4 lint

Maschinen Instruktion

MOVZBD ch, lint

• Verlust von Programmflussinformationen
• Verlust der Blockstruktur
• Verlust von Typinformationen

Semantik-Dictionary-Encoding

Semantisches Vokabular

Index	Class	Info	Links
n-1	...
n	variable	a
n+1	variable	b
n+2	variable	c
n+3	multiplication		n+1, n+2
n+4	addition		n, n+3
n+5	...
...

Tabelle 4: Semantisches Vokabular des obigen Beispiels

Oberon Source-Code

MODULE M;

VAR i, j, k: INTEGER;

PROCEDURE P(x: INTEGER):INTEGER;
BEGIN


...

END P;

BEGIN


i := P(i);


i := i+j;


j := i+k;


k := i+j;


i ;= i+j;

END M.

Symbol Vokabular

Index	Class	Meaning	Missing
asgn	assignment	. := .	left, right
plus	addition	. + .	left, right
...	...	...	...
vi	variable	i	-
vj	variable	j	-
vk	variable	k	-
refp	adress	P	-
callp	function call	P(.)	left
entp	entry	P-BEGIN	-
retp	return	P-RETURN	left
...	...	...	...

Tabelle 5: Semantisches Vokabular

Instruktions Sequenz

   asgn vi callp vi               i := P(i)

   asgn vi plus  vi vj            i := i + j

   asgn vj plus  vj vk            j := i + k

   asgn vk plus  vi vj            k := i + j

   asgn vi plus  vi vj            i := i + j

SDE mit heuristik

Symbol Vokabular

Index	Class	Meaning	Missing
...	...	...	...
n	function call	P(i)	-
n+1	assignment	i := .	right
n+2	assignment	i := P(i)	-
n+3	addition	i + .	right
n+4	addition	. + j	left
n+5	addition	i + j	-
n+6	assignment	i := i + j	-
n+7	addition	. + k	left
n+8	addition	i + k	-
n+9	assignment	j := .	right
n+10	assignment	j := i + k	-
n+11	assignment	k := .	right
n+12	assignment	k := i + j	-
...	...	...	...

Tabelle 6: Erweitertes semantisches Vokabular

Instruktions Sequenz

    asgn vi  callp vi                 i := P(i)

    n+1      plus  vi vj              i := i + j

    asgn vj  n+3   vk                 j := i + k

    asgn vk  n+5                      k := i + j

    n+6                               i := i + j

Es werden nur 16 von 24 Einträgen benutzt.