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; UPD ID= 3550 on 5/14/81 at 1:29 PM by NIXON                           
TITLE	DPSUB FOR LIBOL
SUBTTL	DOUBLE-PRECISION INTEGER SUBTRACTION	PETE WILSON/ALB/CAM



;THIS SOFTWARE IS FURNISHED UNDER A LICENSE AND MAY ONLY BE USED
;  OR COPIED IN ACCORDANCE WITH THE TERMS OF SUCH LICENSE.
;
;COPYRIGHT (C) 1974, 1981 BY DIGITAL EQUIPMENT CORPORATION


;V10*********
;	5/10/75	/DBT	ADD BIS
;*************

	SEARCH	LBLPRM
	%%LBLP==%%LBLP
	BIS==:BIS

	HISEG

;CALLING SEQUENCE:
;	MOVE 16,<Z AC,OPERAND B>
;	PUSHJ 17,SUB.12/SUB.21/SUB.22

;ENTER WITH FIRST OPERAND (OPERAND A) IN ACCUMULATOR SPECIFIED BY AC-FIELD OF PARAMETER
;SECOND OPERAND (OPERAND B) IS ACCESSED VIA AC 16 (WHERE THE UUO IS).
; IF DOUBLE-PRECISION:
;	0(16) GETS HIGH-ORDER WORD, 1(16) REFERENCES LOW HALF.
; IF SINGLE-PRECISION:
;	0(16) REFERENCES SINGLE WORD.
;EXIT WITH TWO-WORD RESULT IN AC'S SPECIFIED BY AC-FIELD OF PARAMETER

	ENTRY	SUB.12	;SUB TWO WORDS IN MEMORY FROM ONE WORD IN AC 1.
	ENTRY	SUB.21	;SUB ONE WORD IN MEMORY FROM TWO WORDS IN AC'S 0 AND 1.
	ENTRY	SUB.22	;SUB TWO WORDS IN MEMORY FROM TWO WORDS IN AC'S 0 AND 1.

RS=11		;RESULT AC POINTER
TA=13		;TEMPORARY
TB=14		;TEMPORARY
TC=15		;TEMPORARY
PA=16		;POINTER TO OPERAND B.
PP=17		;PUSH-DOWN POINTER.

IFE	BIS,<

SUB.21:	SKIPGE	0(PA)		;SUB SINGLE TO DOUBLE, CHECK SIGN OF LOW B OPERAND.
	TDZA	TC,TC		;MAKE SIGN OF HIGH-ORDER B OPERAND AGREE
	SETO	TC,		;  WITH LOW-ORDER SIGN.
	SOJA	PA,SUBXX	;THEN ADJUST POINTER AND ENTER MAIN LINE.

SUB.12:	LDB	RS,[POINT 4,PA,12]	;GET INPUT AC
	MOVE	TA,0(RS)	;GET OPERAND
	MULI	TA,1		;CREATE DOUBLE-PRECISION
	SETCM	TC,0(PA)	;GET HI-PART OF OTHER OPERAND
	JRST	SUBXX1

SUB.22:	SETCM	TC,0(PA)	;SUB DOUBLE TO DOUBLE, GET HIGH-ORDER B WORD.

SUBXX:	LDB	RS,[POINT 4,PA,12] ;GET OPERAND AC
	MOVE	TA,0(RS)	;GET OPERAND
	MOVE	TB,1(RS)
SUBXX1:	JFCL	17,.+1		;CLEAR ARITHMETIC FLAGS.
	PUSHJ	PP,CHECK	;BE SURE SIGNS AGREE
	SUB	TB,1(PA)	;SUB LOW-ORDER WORDS.
	JCRY1	CARRYS		;IF A CARRY OCCURRED, GO ADJUST HIGH-ORDER WORD.
SUBXX2:	ADD	TA,TC		;SUB TWO HIGH-ORDER WORDS.
	PUSHJ	PP,CHECK	;BE SURE SIGNS AGREE
	MOVEM	TA,0(RS)	;STASH HI-PART
	MOVEM	TB,1(RS)	;STASH LOW PART
	POPJ	PP,		;RETURN

CHECK:	TLNE	TA,1B18		;MAKE SIGN OF LOW-ORDER PART
	TLOA	TB,1B18		;  AGREE WITH SIGN OF
	TLZ	TB,1B18		;  HIGH-ORDER RESULT.
	POPJ	PP,

;COME HERE ON CARRY GENERATED IN ADDITION OF LOW-ORDER WORDS.
CARRYS:	ADDI	TA,1		;ADD CARRY TO HIGH-ORDER HALF.
	PUSHJ	PP,CHECK	;THEN GO CHECK FOR SIGN CHANGE IN HIGH HALF.
	JFCL	17,SUBXX2	;CLEAR OVERFLOW AND GO ADD HIGH-ORDER WORDS.

>	;END OF NON-BIS

IFN	BIS,<

SUB.12:
	LDB	TA,PACFL.##	; GET AC NUMBER
	MOVE	TB,(TA)		;GET THE LOW ORDER WORD.
	MOVEM	TB,1(TA)	;PUT IT WHERE IT SHOULD BE.
	SETZM	(TA)		;CLEAR HIGH ORDER AC
	SKIPGE	1(TA)		;IS LOW ORDER NEGATIVE
	SETOM	(TA)		;YES - EXTEND SIGN

SUB.22:
	;CHANGE PA INTO A DSUB

	TLZ	PA,777000	;JUST TO BE SAFE
	TLO	PA,(DSUB)		;PUT IN OP CODE
	XCT	PA		;DO IT
	POPJ	PP,		;DONE

SUB.21:
	MOVE	TA,0(PA)	;GET WORD IN MEMORY
	ASHC	TA,-^D35	;EXTEND SIGN
	HRRI	PA,TA		;WE WILL ADD IN TA
	TLZ	PA,777000	;JUST TO BE SURE
	TLO	PA,(DSUB)	;SET OP CODE
	XCT	PA
	POPJ	PP,		;DONE

>	;END BIS

	END