date and time created 85/07/31 21:33:42 by sam

SCCS-vsn: sys/tahoe/math/Kmuld.s 1.1

diff --git a/usr/src/sys/tahoe/math/Kmuld.s b/usr/src/sys/tahoe/math/Kmuld.s
new file mode 100644 (file)
index 0000000..7ef34f5
--- /dev/null
+++ b/usr/src/sys/tahoe/math/Kmuld.s
@@ -0,0 +1,112 @@
+
+#include       "fp.h"
+#include       "fp_in_krnl.h"
+
+
+                       /* here we count from 0 not from 1 as in fp.h */
+#define        HIDDEN  23      
+
+       .text
+       .globl  _Kmuld      # _Kmuld(acc_most,acc_least,op_most,op_least,hfs)
+_Kmuld:        .word   0xffc
+       clrl    r3              /* r3 - sign: 0 for positive,1 for negative. */
+       movl    4(fp),r0
+       jgeq    1f
+       movl    $1,r3
+1:     movl    12(fp),r2
+       jgeq    2f
+       bbc     $0,r3,1f        /* seconed operand is negative. */
+       clrl    r3              /* if first was negative, make result positive. */
+       jmp     2f
+1:     movl    $1,r3           /* if first was positive, make result negative. */
+2:     andl2   $EXPMASK,r0     /* compute first 'pure'exponent. */
+       jeql    retzero
+       shrl    $EXPSHIFT,r0,r0
+       subl2   $BIASP1,r0      
+       andl2   $EXPMASK,r2     /* compute seconed 'pure'exponent. */
+       jeql    retzero
+       shrl    $EXPSHIFT,r2,r2
+       subl2   $BIASP1,r2
+       addl2   r0,r2           /* add the exponents. */
+       addl2   $(BIASP1+2),r2
+       jleq    underflow
+       cmpl    r2,$258         /* normalization can make the exp. smaller. */
+       jgeq    overflow
+ /*
+ *     We have the sign in r3,the exponent in r2,now is the time to
+ *     perform the multiplication...
+ */
+       /* fetch first fraction: (r0,r1) */
+       andl3   $(0!(EXPMASK | SIGNBIT)),4(fp),r0
+       orl2    $(0!CLEARHID),r0
+       movl    8(fp),r1
+       shlq    $7,r0,r0        /* leave the sign bit cleared. */
+ 
+       /* fetch seconed fraction: (r4,r5) */
+       andl3   $(0!(EXPMASK | SIGNBIT)),12(fp),r4
+       orl2    $(0!CLEARHID),r4
+       movl    16(fp),r5
+       shlq    $7,r4,r4        /* leave the sign bit cleared. */
+
+       /* in the following lp1 stands for least significant part of operand 1,
+       *                  lp2 for least significant part of operand 2,
+       *                  mp1 for most significant part of operand 1,
+       *                  mp2 for most significant part of operand 2.
+       */
+ 
+       clrl    r6
+       shrl    $1,r1,r1        /* clear the sign bit of the lp1. */
+       jeql    1f
+       emul    r1,r4,$0,r6     /* r6,r7 <-- lp1*mp2 */
+       shlq    $1,r6,r6        /* to compensate for the shift we did to clear the sign bit. */
+1:     shrl    $1,r5,r5        /* clear the sign bit of the lp2. */
+       jeql    1f
+       emul    r0,r5,$0,r8     /* r8,r9 <-- mp1*lp2 */
+       shlq    $1,r8,r8
+       addl2   r9,r7           /* r6,r7 <-- the sum of the products. */
+       adwc    r8,r6
+1:     emul    r0,r4,$0,r0     /* r0,r1 <-- mp1*mp2  */
+       addl2   r6,r1           /* add the most sig. part of the sum. */
+       adwc    $0,r0
+       movl    r0,r4           /* to see how much we realy need to shift. */
+       movl    $6,r5           /* r5 - shift counter. */
+       shrl    $7,r4,r4        /* dummy shift. */
+1:     bbs     $HIDDEN,r4,realshift
+       shll    $1,r4,r4
+       decl    r2              /* update exponent. */
+       jeql    underflow
+       decl    r5              /* update shift counter. */
+       jmp     1b
+realshift:
+       shrq    r5,r0,r0
+       bbc     $0,r1,shiftmore
+       incl    r1              /* rounding. */
+shiftmore:
+       shrq    $1,r0,r0
+comb:
+       andl2   $CLEARHID,r0
+       shll    $EXPSHIFT,r2,r4
+       orl2    r4,r0
+       cmpl    r2,$256
+       jlss    1f
+       orl2    $HFS_OVF,*20(fp)        
+sign:
+1:     bbc     $0,r3,done
+       orl2    $SIGNBIT,r0
+done:  ret
+
+
+
+  retzero:
+         clrl  r0
+         clrl  r1
+         ret
+  overflow:
+       orl2    $HFS_OVF,*20(fp)
+       ret
+  underflow:
+       orl2    $HFS_UNDF,*20(fp)
+       ret
+
+
+