;
; $Id: numbitvx.s,v 1.1.1.1 1996/02/15 17:47:48 mclareni Exp $
;
; $Log: numbitvx.s,v $
; Revision 1.1.1.1  1996/02/15 17:47:48  mclareni
; Kernlib
;
;
 .TITLE  NUMBIT -- RETURNS THE NUMBER OF 1 BITS IN THE ARGUMENT.
;
;       ROUTINE NUMBIT - CERNLIB ROUTINE M429
;
;       NUMBIT FINDS THE NUMBER OF 1 BITS IN THE ARGUMENT WORD.
;
;       THIS ROUTINE WORKS IN THE FOLLOWING MANNER. IT FIRST VERIFYS
;       THAT THE ARGUMENT IS NON-ZERO. IF NOT, IT RETURNS ZERO. IT THEN
;       PERFORMS THE THE FOLLOWING STEPS FOR EACH SET BIT.
;       1) IT CLEARS THE LOWEST ORDER BIT BY ANDING THE WORKING COPY
;          OF THE ARGUMENT WITH THE COMPLEMENT OF ITS NEGATIVE.
;       2) IT INCREMENTS A BIT COUNTER.
;       THIS LOOP CONTINUES UNTIL THE WORKING COPY OF THE ARGUMENT IS
;       ZERO (ALL BITS HAVE BEEN CLEARED). THE BIT COUNTER THEN CONTAINS
;       THE DESIRED VALUE.
;
;       REVISION HISTORY
;
;       DATE      AUTHOR    CHANGES
;       ----      ------    -------
;     2-MAY-83  J. ZWEIZIG  ORIGINAL VERSION
;
;

        .PSECT  $CODE,PIC,CON,REL,LCL,SHR,EXE,RD,NOWRT,LONG

        .ENTRY  NUMBIT,^M<R2>

        CLRL    R0                      ; ZERO THE STARTING VALUE
        MOVL    @4(AP),R1               ; GET THE ARGUMENT VALUE
        BEQL    2$                      ; MAKE SURE ONE BIT IS SET
1$:     INCL    R0                      ; INCREMENT THE BIT COUNT.
        MNEGL   R1,R2                   ; DELETE THE LOWEST ORDER BIT
        BICL    R2,R1                   ;  BY ANDING THE NUMBER WITH
                                        ;  THE COMPLEMENT OF ITS NEGATIVE.
        BNEQ    1$                      ; REPEAT FOR THE REST OF THE BITS

2$:     RET

        .END