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Regularize padding of signed constants 

Factor common code for processing signed constants to be padded.
In the process, fix some minor bugs in the padding decisions.

Signed-off-by: Stephen Williams <steve@icarus.com>
This commit is contained in:
Stephen Williams 2007-10-15 20:17:06 -07:00
parent 7bba276a79
commit 27b704b054
2 changed files with 5 additions and 31 deletions
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22
elab_net.cc
View File

@ -2620,25 +2620,9 @@ NetNet* PENumber::elaborate_net(Design*des, NetScope*scope,
net->local_flag(true);
net->set_signed(value_->has_sign());
/* when expanding a constant to fit into the net, extend
the Vx or Vz values if they are in the sign position,
otherwise extend the number with 0 bits. */
verinum::V top_v = verinum::V0;
switch (value_->get(value_->len()-1)) {
case verinum::Vx:
top_v = verinum::Vx;
break;
case verinum::Vz:
top_v = verinum::Vz;
break;
default: /* V0 and V1, do nothing */
break;
}
verinum num(top_v, net->vector_width());
unsigned idx;
for (idx = 0 ; idx < num.len() && idx < value_->len(); idx += 1)
num.set(idx, value_->get(idx));
verinum num = pad_to_width(*value_, lwidth);
if (num.len() > lwidth)
num = verinum(num, lwidth);
NetConst*tmp = new NetConst(scope, scope->local_symbol(), num);
tmp->pin(0).drive0(drive0);

14
pad_to_width.cc
View File

@ -25,6 +25,7 @@
# include "netlist.h"
# include "netmisc.h"
/*
* This function transforms an expression by padding the high bits
* with V0 until the expression has the desired width. This may mean
@ -39,18 +40,7 @@ NetExpr*pad_to_width(NetExpr*expr, unsigned wid)
/* If the expression is a const, then replace it with a wider
const. This is a more efficient result. */
if (NetEConst*tmp = dynamic_cast<NetEConst*>(expr)) {
verinum eval = tmp->value();
bool signed_flag = eval.has_sign();
verinum::V pad = verinum::V0;
if (signed_flag)
pad = eval.get(eval.len()-1);
verinum oval (pad, wid, eval.has_len());
for (unsigned idx = 0 ; idx < eval.len() ; idx += 1)
oval.set(idx, eval.get(idx));
oval.has_sign(signed_flag);
verinum oval = pad_to_width(tmp->value(), wid);
tmp = new NetEConst(oval);
delete expr;
return tmp;