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macc: Stop using the B port

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The B port is for single-bit summands. These can just as well be
represented as an additional summand on the A port (which supports
summands of arbitrary width). An upcoming `$macc_v2` cell won't be
special-casing single-bit summands in any way.

In preparation, make the following changes:

 * remove the `bit_ports` field from the `Macc` helper (instead add any
   single-bit summands to `ports` next to other summands)

 * leave `B` empty on cells emitted from `Macc::to_cell`
This commit is contained in:
Martin Povišer 2024-12-13 18:10:10 +01:00 • committed by Emil J. Tywoniak
parent 8fd40942e9
commit 652a1b9806
10 changed files with 89 additions and 51 deletions
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32
kernel/macc.h
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@ -30,14 +30,11 @@ struct Macc
RTLIL::SigSpec in_a, in_b;
bool is_signed, do_subtract;
};
std::vector<port_t> ports;
RTLIL::SigSpec bit_ports;
void optimize(int width)
{
std::vector<port_t> new_ports;
RTLIL::SigSpec new_bit_ports;
RTLIL::Const off(0, width);
for (auto &port : ports)
@ -48,11 +45,6 @@ struct Macc
if (GetSize(port.in_a) < GetSize(port.in_b))
std::swap(port.in_a, port.in_b);
if (GetSize(port.in_a) == 1 && GetSize(port.in_b) == 0 && !port.is_signed && !port.do_subtract) {
bit_ports.append(port.in_a);
continue;
}
if (port.in_a.is_fully_const() && port.in_b.is_fully_const()) {
RTLIL::Const v = port.in_a.as_const();
if (GetSize(port.in_b))
@ -79,12 +71,6 @@ struct Macc
new_ports.push_back(port);
}
for (auto &bit : bit_ports)
if (bit == State::S1)
off = const_add(off, RTLIL::Const(1, width), false, false, width);
else if (bit != State::S0)
new_bit_ports.append(bit);
if (off.as_bool()) {
port_t port;
port.in_a = off;
@ -94,7 +80,6 @@ struct Macc
}
new_ports.swap(ports);
bit_ports = new_bit_ports;
}
void from_cell(RTLIL::Cell *cell)
@ -102,7 +87,6 @@ struct Macc
RTLIL::SigSpec port_a = cell->getPort(ID::A);
ports.clear();
bit_ports = cell->getPort(ID::B);
auto config_bits = cell->getParam(ID::CONFIG);
int config_cursor = 0;
@ -145,6 +129,9 @@ struct Macc
ports.push_back(this_port);
}
for (auto bit : cell->getPort(ID::B))
ports.push_back(port_t{{bit}, {}, false, false});
log_assert(config_cursor == config_width);
log_assert(port_a_cursor == GetSize(port_a));
}
@ -190,11 +177,11 @@ struct Macc
}
cell->setPort(ID::A, port_a);
cell->setPort(ID::B, bit_ports);
cell->setPort(ID::B, {});
cell->setParam(ID::CONFIG, config_bits);
cell->setParam(ID::CONFIG_WIDTH, GetSize(config_bits));
cell->setParam(ID::A_WIDTH, GetSize(port_a));
cell->setParam(ID::B_WIDTH, GetSize(bit_ports));
cell->setParam(ID::B_WIDTH, 0);
}
bool eval(RTLIL::Const &result) const
@ -219,19 +206,12 @@ struct Macc
result = const_add(result, summand, port.is_signed, port.is_signed, GetSize(result));
}
for (auto bit : bit_ports) {
if (bit.wire)
return false;
result = const_add(result, bit.data, false, false, GetSize(result));
}
return true;
}
bool is_simple_product()
{
return bit_ports.empty() &&
ports.size() == 1 &&
return ports.size() == 1 &&
!ports[0].in_b.empty() &&
!ports[0].do_subtract;
}