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/*
* nextpnr -- Next Generation Place and Route
*
* Copyright (C) 2021 The SymbiFlow Authors.
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
*/
#ifndef EXCLUSIVE_STATE_GROUPS_H
#define EXCLUSIVE_STATE_GROUPS_H
#include <array>
#include <bitset>
#include <cstdint>
#include <limits>
#include <vector>
#include "archdefs.h"
#include "bits.h"
#include "idstring.h"
#include "nextpnr_assertions.h"
#include "nextpnr_namespaces.h"
NEXTPNR_NAMESPACE_BEGIN
// Implementation for exclusive state groups, used to implement generic
// constraint system.
template <size_t StateCount, typename StateType = int8_t, typename CountType = uint8_t> struct ExclusiveStateGroup
{
ExclusiveStateGroup() : state(kNoSelected) { count.fill(0); }
struct Definition
{
IdString prefix;
IdString default_state;
std::vector<IdString> states;
};
static_assert(StateCount < std::numeric_limits<StateType>::max(), "StateType cannot store max StateType");
static_assert(std::numeric_limits<StateType>::is_signed, "StateType must be signed");
std::bitset<StateCount> selected_states;
StateType state;
std::array<CountType, StateCount> count;
static constexpr StateType kNoSelected = -1;
static constexpr StateType kOverConstrained = -2;
std::pair<bool, IdString> current_state(const Definition &definition) const
{
if (state <= 0) {
return std::make_pair(state == kNoSelected, definition.default_state);
} else {
NPNR_ASSERT(state <= definition.states.size());
return std::make_pair(true, definition.states[state]);
}
}
bool check_implies(int32_t next_state) const
{
// Implies can be satified if either that state is
// selected, or no state is currently selected.
return state == next_state || state == kNoSelected;
}
bool add_implies(int32_t next_state)
{
NPNR_ASSERT(next_state >= 0 && (size_t)next_state < StateCount);
// Increment and mark the state as selected.
count[next_state] += 1;
selected_states[next_state] = true;
if (state == next_state) {
// State was already selected, state group is still satified.
return true;
} else if (selected_states.count() == 1) {
// State was not select selected, state is now selected.
// State group is satified.
state = next_state;
return true;
} else {
// State group is now overconstrained.
state = kOverConstrained;
return false;
}
};
void remove_implies(int32_t next_state)
{
NPNR_ASSERT(next_state >= 0 && (size_t)next_state < StateCount);
NPNR_ASSERT(selected_states[next_state]);
count[next_state] -= 1;
NPNR_ASSERT(count[next_state] >= 0);
// Check if next_state is now unselected.
if (count[next_state] == 0) {
// next_state is not longer selected
selected_states[next_state] = false;
// Check whether the state group is now unselected or satified.
auto value = selected_states.to_ulong();
auto number_selected = Bits::popcount(value);
if (number_selected == 1) {
// Group is no longer overconstrained.
state = Bits::ctz(value);
NPNR_ASSERT(selected_states[state]);
} else if (number_selected == 0) {
// Group is unselected.
state = kNoSelected;
} else {
state = kOverConstrained;
}
}
}
template <typename StateRange> bool requires(const StateRange &state_range) const
{
if (state < 0) {
return false;
}
for (const auto required_state : state_range) {
if (state == required_state) {
return true;
}
}
return false;
}
void print_debug(const Context *ctx, IdString object, const Definition &definition) const;
void explain_implies(const Context *ctx, IdString object, IdString cell, const Definition &definition, BelId bel,
int32_t next_state) const;
template <typename StateRange>
void explain_requires(const Context *ctx, IdString object, IdString cell, const Definition &definition, BelId bel,
const StateRange state_range) const;
};
NEXTPNR_NAMESPACE_END
#endif
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