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Simpler implementation of multiplication.

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1 parent aae1704 commit 380d5620e69d20a25e5cb9f61286813f1a761178 steve committed Mar 4, 2000
Showing with 49 additions and 14 deletions.
  1. +49 −14 vvm/vvm_mult.cc
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63 vvm/vvm_mult.cc
@@ -17,7 +17,7 @@
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#if !defined(WINNT) && !defined(macintosh)
-#ident "$Id: vvm_mult.cc,v 1.2 2000/02/23 02:56:57 steve Exp $"
+#ident "$Id: vvm_mult.cc,v 1.3 2000/03/04 01:13:54 steve Exp $"
#endif
# include "vvm_gates.h"
@@ -27,20 +27,52 @@ void vvm_binop_mult(vpip_bit_t*r, unsigned nr,
const vpip_bit_t*a, unsigned na,
const vpip_bit_t*b, unsigned nb)
{
- assert(nr >= (na+nb));
-
- for (unsigned idx = 0 ; idx < nr ; idx += 1)
- r[idx] = V0;
-
- for (unsigned bdx = 0 ; bdx < nb ; bdx += 1) {
- unsigned rdx = bdx;
- vpip_bit_t c = V0;
- for (unsigned idx = 0 ; idx < na ; idx += 1) {
- r[rdx] = add_with_carry(r[rdx],a[idx]&b[bdx],c);
- rdx += 1;
- }
- if (rdx < nr) r[rdx] = add_with_carry(r[rdx],c,c);
+ assert(nr <= 8*sizeof(unsigned long));
+ assert(na <= 8*sizeof(unsigned long));
+ assert(nb <= 8*sizeof(unsigned long));
+
+ unsigned long av = 0, bv = 0;
+ unsigned long rv;
+
+ for (unsigned idx = 0 ; idx < na ; idx += 1) switch (a[idx]) {
+
+ case V0:
+ break;
+ case V1:
+ av |= 1 << idx;
+ break;
+ default:
+ goto unknown_result;
}
+
+ for (unsigned idx = 0 ; idx < nb ; idx += 1) switch (b[idx]) {
+
+ case V0:
+ break;
+ case V1:
+ bv |= 1 << idx;
+ break;
+ default:
+ goto unknown_result;
+ }
+
+ rv = av * bv;
+
+ for (unsigned idx = 0 ; idx < nr ; idx += 1) {
+
+ if (rv & 1)
+ r[idx] = V1;
+ else
+ r[idx] = V0;
+
+ rv >>= 1;
+ }
+
+ return;
+
+ unknown_result:
+ for (unsigned idx= 0 ; idx < nr ; idx += 1)
+ r[idx] = Vx;
}
vvm_mult::vvm_mult(unsigned rwid, unsigned awid,
@@ -107,6 +139,9 @@ void vvm_mult::set_DataB(unsigned idx, vpip_bit_t val)
/*
* $Log: vvm_mult.cc,v $
+ * Revision 1.3 2000/03/04 01:13:54 steve
+ * Simpler implementation of multiplication.
+ *
* Revision 1.2 2000/02/23 02:56:57 steve
* Macintosh compilers do not support ident.
*

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