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/*
* nextpnr -- Next Generation Place and Route
*
* Copyright (C) 2021 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 LOOKAHEAD_H
#define LOOKAHEAD_H
#include <algorithm>
#include <vector>
#include "cost_map.h"
#include "deterministic_rng.h"
#include "hash_table.h"
#include "lookahead.capnp.h"
#include "nextpnr_namespaces.h"
#include "type_wire.h"
NEXTPNR_NAMESPACE_BEGIN
// Lookahead is a routing graph generic lookahead builder and evaluator.
//
// The lookahead data model is structured into 3 parts:
// - Output site wires to routing network cost
// - Routing network point to point cost
// - Routing network cost to input site wires
//
// If the lookahead is invoked from a routing wire to a routing wire, only
// the point to point cost is used.
//
// If the lookahead is invoked from an output site wire to a routing wire,
// the point to point cost is computed using the cheapest output routing wire
// from the current site wire and then returned cost is the sum of the output
// cost plus the point to point routing network cost.
//
// If the lookahead is invoked from a routing wire to an input site wire,
// then the cost is the point to point routing cost to the cheapest input
// routing wire plus the input routing cost.
//
// If the lookahead is invoked from an output site wire to an input site wire,
// then cost is the sum of each of the 3 parts.
struct Lookahead
{
void init(const Context *, DeterministicRNG *rng);
void build_lookahead(const Context *, DeterministicRNG *rng);
bool read_lookahead(const std::string &chipdb_hash, const std::string &file);
void write_lookahead(const std::string &chipdb_hash, const std::string &file) const;
bool from_reader(const std::string &chipdb_hash, lookahead_storage::Lookahead::Reader reader);
void to_builder(const std::string &chipdb_hash, lookahead_storage::Lookahead::Builder builder) const;
delay_t estimateDelay(const Context *, WireId src, WireId dst) const;
struct InputSiteWireCost
{
// This wire is the cheapest non-site wire that leads to this site
// wire.
TypeWireId route_to;
// This is the cost from the cheapest_route_to wire to the site wire in
// question.
delay_t cost;
};
struct OutputSiteWireCost
{
// This wire is the cheapest non-site wire that is reachable from
// this site wire.
TypeWireId cheapest_route_from;
// This is the cost from the site wire in question to
// cheapest_route_from wire.
delay_t cost;
};
HashTables::HashMap<TypeWireId, std::vector<InputSiteWireCost>> input_site_wires;
HashTables::HashMap<TypeWireId, OutputSiteWireCost> output_site_wires;
HashTables::HashMap<TypeWirePair, delay_t> site_to_site_cost;
CostMap cost_map;
};
NEXTPNR_NAMESPACE_END
#endif /* LOOKAHEAD_H */
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