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Fix cprop merging of part selects to be 2-state aware. 

When driving a 2-state net, any undriven bits in the concatenation
of part selects should be driven to '0', not 'z'. This saves having
to cast the result.
This commit is contained in:
Martin Whitaker 2024-01-27 13:34:36 +00:00
parent d0af41442b
commit b037d6aef9
1 changed files with 18 additions and 6 deletions
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24
cprop.cc
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@ -1,5 +1,5 @@
/*
* Copyright (c) 1998-2021 Stephen Williams (steve@icarus.com)
* Copyright (c) 1998-2024 Stephen Williams (steve@icarus.com)
*
* This source code is free software; you can redistribute it
* and/or modify it in source code form under the terms of the GNU
@ -219,15 +219,23 @@ void cprop_functor::lpm_part_select(Design*des, NetPartSelect*obj)
Nexus*nex = obj->pin(1).nexus();
vector<NetPartSelect*> obj_set;
bool output_2_state = false;
for (Link*cur = nex->first_nlink() ; cur ; cur = cur->next_nlink()) {
NetPins*tmp_obj = cur->get_obj();
// Record if we are driving a 2-state net.
NetNet*net_obj = dynamic_cast<NetNet*> (tmp_obj);
if (net_obj && (net_obj->data_type() == IVL_VT_BOOL))
output_2_state = true;
// If this is an input (or passive) then ignore it.
if (cur->get_dir() != Link::OUTPUT)
continue;
// Check to see if this is the output of a
// NetPartSelect::PV. If not, then give up on the blend.
NetPins*tmp_obj = cur->get_obj();
unsigned tmp_pin = cur->get_pin();
NetPartSelect*cur_obj = dynamic_cast<NetPartSelect*> (tmp_obj);
@ -307,8 +315,10 @@ void cprop_functor::lpm_part_select(Design*des, NetPartSelect*obj)
for (size_t idx = 0 ; idx < obj_set.size() ; idx += 1) {
NetPartSelect*cobj = obj_set[idx];
if (cobj->base() > off) {
NetNet*zzz = make_const_z(des, scope, cobj->base()-off);
connect(cncat->pin(concat_pin), zzz->pin(0));
NetNet*val = output_2_state
? make_const_0(des, scope, cobj->base()-off)
: make_const_z(des, scope, cobj->base()-off);
connect(cncat->pin(concat_pin), val->pin(0));
concat_pin += 1;
off = cobj->base();
}
@ -317,8 +327,10 @@ void cprop_functor::lpm_part_select(Design*des, NetPartSelect*obj)
off += cobj->width();
}
if (off < sig_width) {
NetNet*zzz = make_const_z(des, scope, sig_width-off);
connect(cncat->pin(concat_pin), zzz->pin(0));
NetNet*val = output_2_state
? make_const_0(des, scope, sig_width-off)
: make_const_z(des, scope, sig_width-off);
connect(cncat->pin(concat_pin), val->pin(0));
concat_pin += 1;
}
ivl_assert(*obj, concat_pin == cncat->pin_count());