luke
/
iverilog
mirror of https://github.com/steveicarus/iverilog.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Minor rework of summation carry propagation (Stephan Boettcher)

This commit is contained in:
steve 2001-10-27 03:22:26 +00:00
parent 8c9e0bafa9
commit 96a50d635d
2 changed files with 31 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

48
vvp/arith.cc
View File

@ -17,7 +17,7 @@
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#if !defined(WINNT)
#ident "$Id: arith.cc,v 1.16 2001/10/16 03:10:20 steve Exp $"
#ident "$Id: arith.cc,v 1.17 2001/10/27 03:22:26 steve Exp $"
#endif
# include "arith.h"
@ -263,19 +263,19 @@ void vvp_arith_sum::set(vvp_ipoint_t i, functor_t f, bool push)
if (ival & 0x40)
tmp += 1;
// Add in the carry carried over.
assert(tmp < (ULONG_MAX/2));
tmp += carry;
// Put the next bit into the sum,
sum_[page] |= ((tmp&1) << pbit);
// ... and carry the remaining bits.
carry = tmp >> 1;
// Save carry bits
if (pbit >= pagesize - 2)
carry += (tmp + (sum_[page]>>pbit)) >> (pagesize-pbit);
// Put the next bit into the sum,
sum_[page] += tmp << pbit;
pbit += 1;
if (pbit == 8 * sizeof sum_[page]) {
if (pbit >= pagesize) {
pbit = 0;
page += 1;
sum_[page] = 0;
sum_[page] = carry;
carry = 0;
}
}
@ -326,13 +326,12 @@ void vvp_arith_sub::set(vvp_ipoint_t i, functor_t f, bool push)
{
unsigned page = 0;
unsigned pbit = 0;
unsigned long carry = 0;
/* There are 3 values subtracted from the first parameter, so
there are three 2s complements, so three ~X +1. That's why
the carry starts with 3. */
unsigned long carry = 3;
sum_[0] = 0;
the sum_ starts with 3. */
sum_[0] = 3;
for (unsigned idx = 0 ; idx < wid_ ; idx += 1) {
vvp_ipoint_t ptr = ipoint_index(base_,idx);
@ -356,19 +355,19 @@ void vvp_arith_sub::set(vvp_ipoint_t i, functor_t f, bool push)
if (! (ival & 0x40))
tmp += 1;
// Add in the carry carried over.
assert(tmp < (ULONG_MAX/2));
tmp += carry;
// Put the next bit into the sum,
sum_[page] |= ((tmp&1) << pbit);
// ... and carry the remaining bits.
carry = tmp >> 1;
// Save carry bits
if (pbit >= pagesize - 2)
carry += (tmp + (sum_[page]>>pbit)) >> (pagesize-pbit);
// Put the next bits into the sum,
sum_[page] += tmp << pbit;
pbit += 1;
if (pbit == 8 * sizeof sum_[page]) {
if (pbit >= pagesize) {
pbit = 0;
page += 1;
sum_[page] = 0;
sum_[page] = carry;
carry = 0;
}
}
@ -634,6 +633,9 @@ void vvp_shiftr::set(vvp_ipoint_t i, functor_t f, bool push)
/*
* $Log: arith.cc,v $
* Revision 1.17 2001/10/27 03:22:26 steve
* Minor rework of summation carry propagation (Stephan Boettcher)
*
* Revision 1.16 2001/10/16 03:10:20 steve
* Get Division error into the division method!
*

7
vvp/arith.h
View File

@ -19,7 +19,7 @@
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#if !defined(WINNT)
#ident "$Id: arith.h,v 1.9 2001/10/16 02:47:37 steve Exp $"
#ident "$Id: arith.h,v 1.10 2001/10/27 03:22:26 steve Exp $"
#endif
# include "functor.h"
@ -81,6 +81,7 @@ class vvp_arith_sum : public vvp_arith_ {
private:
unsigned long*sum_;
static const unsigned pagesize = 8*sizeof(unsigned long);
private: // not implemented
vvp_arith_sum(const vvp_arith_sum&);
@ -97,6 +98,7 @@ class vvp_arith_sub : public vvp_arith_ {
private:
unsigned long*sum_;
static const unsigned pagesize = 8*sizeof(unsigned long);
private: // not implemented
vvp_arith_sub(const vvp_arith_sub&);
@ -159,6 +161,9 @@ class vvp_shiftr : public vvp_arith_ {
/*
* $Log: arith.h,v $
* Revision 1.10 2001/10/27 03:22:26 steve
* Minor rework of summation carry propagation (Stephan Boettcher)
*
* Revision 1.9 2001/10/16 02:47:37 steve
* Add arith/div object.
*