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[unix-history] / usr / src / sys / tahoe / math / Kfnorm.s

/*      Kfnorm.s        1.3     86/01/05        */

#include "../tahoemath/fp.h"
#include "../tahoemath/Kfp.h"
#include "../tahoe/SYS.h"

       .text
ENTRY(Kfnorm, R6|R5|R4|R3|R2)
                               # clrl  r1
       movl    r0,r4           # copy to temporary.
       jneq    inr0
       movl    r1,r5
       clrl    r3              # r3 - pos of m.s.b
inr1:   ffs     r5,r6
       incl    r6
       addl2   r6,r3
       shrl    r6,r5,r5
       jneq    inr1
       cmpl    $0,r3
       jeql    retzero
       jmp     cmpshift
inr0:   movl    $32,r3
inr00:  ffs     r4,r6
       incl    r6
       addl2   r6,r3
       shrl    r6,r4,r4
       jneq    inr00

cmpshift:
                               # compute the shift (r4).
       subl3   r3,$HID_R0R1,r4
       jlss    shiftr          # if less then zero we shift right.
       shlq    r4,r0,r0        # else we shift left.
       subl2   r4,r2           # uodate exponent.
       jleq    underflow       # if less then 0 (biased) it is underflow.
       jmp     combine         # go to combine exponent and fraction.
shiftr:
       mnegl   r4,r4
       shrq    r4,r0,r0        # shift right.
       addl2   r4,r2           # update exponent
       cmpl    r2,$256
       jgeq    overflow        # check for overflow.
combine:
       andl2   $CLEARHID,r0    # clear the hidden bit.
       shal    $EXPSHIFT,r2,r2 # shift the exponent to its proper place.
       orl2    r2,r0
       ret

underflow:
       clrl    r0
       orl2    $HFS_UNDF,*4(fp)        
       ret

overflow:
       orl2    $HFS_OVF,*4(fp)         
       ret
retzero:
       clrl    r0
       clrl    r1
       ret