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/*
* nextpnr -- Next Generation Place and Route
*
* Copyright (C) 2018 David Shah <david@symbioticeda.com>
*
* 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.
*
*/
#include "place_common.h"
#include <cmath>
#include "log.h"
#include "util.h"
NEXTPNR_NAMESPACE_BEGIN
// Get the total estimated wirelength for a net
wirelen_t get_net_metric(const Context *ctx, const NetInfo *net, MetricType type, float &tns)
{
wirelen_t wirelength = 0;
Loc driver_loc;
bool driver_gb;
CellInfo *driver_cell = net->driver.cell;
if (!driver_cell)
return 0;
if (driver_cell->bel == BelId())
return 0;
driver_gb = ctx->getBelGlobalBuf(driver_cell->bel);
driver_loc = ctx->getBelLocation(driver_cell->bel);
WireId drv_wire = ctx->getBelPinWire(driver_cell->bel, ctx->portPinFromId(net->driver.port));
if (driver_gb)
return 0;
float worst_slack = 1000;
int xmin = driver_loc.x, xmax = driver_loc.x, ymin = driver_loc.y, ymax = driver_loc.y;
for (auto load : net->users) {
if (load.cell == nullptr)
continue;
CellInfo *load_cell = load.cell;
if (load_cell->bel == BelId())
continue;
if (ctx->timing_driven && type == MetricType::COST) {
WireId user_wire = ctx->getBelPinWire(load_cell->bel, ctx->portPinFromId(load.port));
delay_t raw_wl = ctx->estimateDelay(drv_wire, user_wire);
float slack = ctx->getDelayNS(load.budget) - ctx->getDelayNS(raw_wl);
if (slack < 0)
tns += slack;
worst_slack = std::min(slack, worst_slack);
}
if (ctx->getBelGlobalBuf(load_cell->bel))
continue;
Loc load_loc = ctx->getBelLocation(load_cell->bel);
xmin = std::min(xmin, load_loc.x);
ymin = std::min(ymin, load_loc.y);
xmax = std::max(xmax, load_loc.x);
ymax = std::max(ymax, load_loc.y);
}
if (ctx->timing_driven && type == MetricType::COST) {
wirelength = wirelen_t((((ymax - ymin) + (xmax - xmin)) * std::min(5.0, (1.0 + std::exp(-worst_slack / 5)))));
} else {
wirelength = wirelen_t((ymax - ymin) + (xmax - xmin));
}
return wirelength;
}
// Get the total wirelength for a cell
wirelen_t get_cell_metric(const Context *ctx, const CellInfo *cell, MetricType type)
{
std::set<IdString> nets;
for (auto p : cell->ports) {
if (p.second.net)
nets.insert(p.second.net->name);
}
wirelen_t wirelength = 0;
float tns = 0;
for (auto n : nets) {
wirelength += get_net_metric(ctx, ctx->nets.at(n).get(), type, tns);
}
return wirelength;
}
wirelen_t get_cell_metric_at_bel(const Context *ctx, CellInfo *cell, BelId bel, MetricType type)
{
BelId oldBel = cell->bel;
cell->bel = bel;
wirelen_t wirelen = get_cell_metric(ctx, cell, type);
cell->bel = oldBel;
return wirelen;
}
// Placing a single cell
bool place_single_cell(Context *ctx, CellInfo *cell, bool require_legality)
{
bool all_placed = false;
int iters = 25;
while (!all_placed) {
BelId best_bel = BelId();
wirelen_t best_wirelen = std::numeric_limits<wirelen_t>::max(),
best_ripup_wirelen = std::numeric_limits<wirelen_t>::max();
CellInfo *ripup_target = nullptr;
BelId ripup_bel = BelId();
if (cell->bel != BelId()) {
ctx->unbindBel(cell->bel);
}
BelType targetType = ctx->belTypeFromId(cell->type);
for (auto bel : ctx->getBels()) {
if (ctx->getBelType(bel) == targetType && (!require_legality || ctx->isValidBelForCell(cell, bel))) {
if (ctx->checkBelAvail(bel)) {
wirelen_t wirelen = get_cell_metric_at_bel(ctx, cell, bel, MetricType::COST);
if (iters >= 4)
wirelen += ctx->rng(25);
if (wirelen <= best_wirelen) {
best_wirelen = wirelen;
best_bel = bel;
}
} else {
wirelen_t wirelen = get_cell_metric_at_bel(ctx, cell, bel, MetricType::COST);
if (iters >= 4)
wirelen += ctx->rng(25);
if (wirelen <= best_ripup_wirelen) {
CellInfo *curr_cell = ctx->cells.at(ctx->getBoundBelCell(bel)).get();
if (curr_cell->belStrength < STRENGTH_STRONG) {
best_ripup_wirelen = wirelen;
ripup_bel = bel;
ripup_target = curr_cell;
}
}
}
}
}
if (best_bel == BelId()) {
if (iters == 0) {
log_error("failed to place cell '%s' of type '%s' (ripup iteration limit exceeded)\n",
cell->name.c_str(ctx), cell->type.c_str(ctx));
}
if (ripup_bel == BelId()) {
log_error("failed to place cell '%s' of type '%s'\n", cell->name.c_str(ctx), cell->type.c_str(ctx));
}
--iters;
ctx->unbindBel(ripup_target->bel);
best_bel = ripup_bel;
} else {
all_placed = true;
}
ctx->bindBel(best_bel, cell->name, STRENGTH_WEAK);
cell = ripup_target;
}
return true;
}
NEXTPNR_NAMESPACE_END
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