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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_legaliser.h"
#include <algorithm>
#include <vector>
#include "cells.h"
#include "design_utils.h"
#include "log.h"
#include "util.h"
NEXTPNR_NAMESPACE_BEGIN
struct CellChain
{
std::vector<CellInfo *> cells;
float mid_x = 0, mid_y = 0;
};
// Generic chain finder
template <typename F1, typename F2, typename F3>
std::vector<CellChain> find_chains(const Context *ctx, F1 cell_type_predicate, F2 get_previous, F3 get_next,
size_t min_length = 2)
{
std::set<IdString> chained;
std::vector<CellChain> chains;
for (auto cell : sorted(ctx->cells)) {
if (chained.find(cell.first) != chained.end())
continue;
CellInfo *ci = cell.second;
if (cell_type_predicate(ctx, ci)) {
CellInfo *start = ci;
CellInfo *prev_start = ci;
while (prev_start != nullptr) {
start = prev_start;
prev_start = get_previous(ctx, start);
}
CellChain chain;
CellInfo *end = start;
while (end != nullptr) {
chain.cells.push_back(end);
end = get_next(ctx, end);
}
if (chain.cells.size() >= min_length) {
chains.push_back(chain);
for (auto c : chain.cells)
chained.insert(c->name);
}
}
}
return chains;
}
static void get_chain_midpoint(const Context *ctx, const CellChain &chain, float &x, float &y)
{
float total_x = 0, total_y = 0;
int N = 0;
for (auto cell : chain.cells) {
if (cell->bel == BelId())
continue;
int bel_x, bel_y;
bool bel_gb;
ctx->estimatePosition(cell->bel, bel_x, bel_y, bel_gb);
total_x += bel_x;
total_y += bel_y;
N++;
}
assert(N > 0);
x = total_x / N;
y = total_y / N;
}
class PlacementLegaliser
{
public:
PlacementLegaliser(Context *ctx) : ctx(ctx){};
bool legalise()
{
init_logic_cells();
bool legalised_carries = legalise_carries();
if (!legalised_carries && !ctx->force)
return false;
return legalised_carries;
}
private:
void init_logic_cells()
{
for (auto bel : ctx->getBels()) {
// Initialise the logic bels vector with unavailable invalid bels, dimensions [0..width][0..height[0..7]
logic_bels.resize(ctx->chip_info->width + 1,
std::vector<std::vector<std::pair<BelId, bool>>>(
ctx->chip_info->height + 1,
std::vector<std::pair<BelId, bool>>(8, std::make_pair(BelId(), true))));
if (ctx->getBelType(bel) == TYPE_ICESTORM_LC) {
// Using the non-standard API here to get (x, y, z) rather than just (x, y)
auto bi = ctx->chip_info->bel_data[bel.index];
int x = bi.x, y = bi.y, z = bi.z;
IdString cell = ctx->getBoundBelCell(bel);
if (cell != IdString() && ctx->cells.at(cell)->belStrength >= STRENGTH_FIXED)
logic_bels.at(x).at(y).at(z) = std::make_pair(bel, true); // locked out of use
else
logic_bels.at(x).at(y).at(z) = std::make_pair(bel, false); // available
}
}
}
bool legalise_carries()
{
std::vector<CellChain> carry_chains = find_chains(
ctx, is_lc,
[](const Context *ctx, const CellInfo *cell) {
return net_driven_by(ctx, cell->ports.at(ctx->id("CIN")).net, is_lc, ctx->id("COUT"));
},
[](const Context *ctx, const CellInfo *cell) {
return net_only_drives(ctx, cell->ports.at(ctx->id("COUT")).net, is_lc, ctx->id("CIN"), false);
});
bool success = true;
// Find midpoints for all chains, before we start tearing them up
std::vector<CellChain> all_chains;
for (auto &base_chain : carry_chains) {
std::vector<CellChain> split_chains = split_carry_chain(base_chain);
for (auto &chain : split_chains) {
get_chain_midpoint(ctx, chain, chain.mid_x, chain.mid_y);
all_chains.push_back(chain);
}
}
// Actual chain placement
for (auto &chain : all_chains) {
float base_x = chain.mid_x, base_y = chain.mid_y - (chain.cells.size() / 16.0f);
// Find Bel meeting requirements closest to the target base, returning location as <x, y, z>
auto chain_origin_bel = find_closest_bel(base_x, base_y, int(chain.cells.size()));
int place_x = std::get<0>(chain_origin_bel), place_y = std::get<1>(chain_origin_bel),
place_z = std::get<2>(chain_origin_bel);
if (place_x == -1) {
if (ctx->force) {
log_warning("failed to place carry chain, starting with cell '%s', length %d\n",
chain.cells.front()->name.c_str(ctx), int(chain.cells.size()));
success = false;
continue;
} else {
log_error("failed to place carry chain, starting with cell '%s', length %d\n",
chain.cells.front()->name.c_str(ctx), int(chain.cells.size()));
}
}
// Place carry chain
for (int i = 0; i < int(chain.cells.size()); i++) {
int target_z = place_y * 8 + place_z + i;
place_lc(chain.cells.at(i), place_x, target_z / 8, target_z % 8);
}
}
return success;
}
// Find Bel closest to a location, meeting chain requirements
std::tuple<int, int, int> find_closest_bel(float target_x, float target_y, int chain_size)
{
std::tuple<int, int, int> best_origin = std::make_tuple(-1, -1, -1);
float smallest_distance = std::numeric_limits<float>::infinity();
int width = ctx->chip_info->width, height = ctx->chip_info->height;
// Slow, should radiate outwards from target position - TODO
for (int x = 1; x < width; x++) {
for (int y = 1; y < (height - (chain_size / 8)); y++) {
bool valid = true;
for (int k = 0; k < chain_size; k++) {
if (logic_bels.at(x).at(y + k / 8).at(k % 8).second) {
valid = false;
break;
}
}
if (valid) {
float distance = (x - target_x) * (x - target_x) + (y - target_y) * (y - target_y);
if (distance < smallest_distance) {
smallest_distance = distance;
best_origin = std::make_tuple(x, y, 0);
}
}
}
}
return best_origin;
}
// Split a carry chain into multiple legal chains
std::vector<CellChain> split_carry_chain(CellChain &carryc)
{
bool start_of_chain = true;
std::vector<CellChain> chains;
std::vector<const CellInfo *> tile;
const int max_length = (ctx->chip_info->height - 2) * 8 - 2;
auto curr_cell = carryc.cells.begin();
while (curr_cell != carryc.cells.end()) {
CellInfo *cell = *curr_cell;
if (tile.size() >= 8) {
tile.clear();
}
if (start_of_chain) {
tile.clear();
chains.emplace_back();
start_of_chain = false;
if (cell->ports.at(ctx->id("CIN")).net) {
// CIN is not constant and not part of a chain. Must feed in from fabric
CellInfo *feedin = make_carry_feed_in(cell, cell->ports.at(ctx->id("CIN")));
chains.back().cells.push_back(feedin);
tile.push_back(feedin);
}
}
tile.push_back(cell);
chains.back().cells.push_back(cell);
bool split_chain = (!ctx->logicCellsCompatible(tile)) || (int(chains.back().cells.size()) > max_length);
if (split_chain) {
CellInfo *passout = make_carry_pass_out(cell->ports.at(ctx->id("COUT")));
tile.pop_back();
chains.back().cells.back() = passout;
start_of_chain = true;
} else {
NetInfo *carry_net = cell->ports.at(ctx->id("COUT")).net;
if (carry_net != nullptr && carry_net->users.size() > 1) {
CellInfo *passout = make_carry_pass_out(cell->ports.at(ctx->id("COUT")));
chains.back().cells.push_back(passout);
tile.push_back(passout);
}
++curr_cell;
}
}
return chains;
}
// Place a logic cell at a given grid location, handling rip-up etc
void place_lc(CellInfo *cell, int x, int y, int z)
{
auto &loc = logic_bels.at(x).at(y).at(z);
assert(!loc.second);
BelId bel = loc.first;
// Check if there is a cell presently at the location, which we will need to rip up
IdString existing = ctx->getBoundBelCell(bel);
if (existing != IdString()) {
// TODO: keep track of the previous position of the ripped up cell, as a hint
rippedCells.insert(existing);
ctx->unbindBel(bel);
}
ctx->bindBel(bel, cell->name, STRENGTH_LOCKED);
loc.second = true; // Bel is now unavailable for further use
}
// Insert a logic cell to legalise a COUT->fabric connection
CellInfo *make_carry_pass_out(PortInfo &cout_port)
{
assert(cout_port.net != nullptr);
std::unique_ptr<CellInfo> lc = create_ice_cell(ctx, ctx->id("ICESTORM_LC"));
lc->params[ctx->id("LUT_INIT")] = "65280"; // 0xff00: O = I3
lc->params[ctx->id("CARRY_ENABLE")] = "1";
lc->ports.at(ctx->id("O")).net = cout_port.net;
NetInfo *co_i3_net = new NetInfo();
co_i3_net->name = ctx->id(lc->name.str(ctx) + "$I3");
co_i3_net->driver = cout_port.net->driver;
PortRef i3_r;
i3_r.port = ctx->id("I3");
i3_r.cell = lc.get();
co_i3_net->users.push_back(i3_r);
PortRef o_r;
o_r.port = ctx->id("O");
o_r.cell = lc.get();
cout_port.net->driver = o_r;
lc->ports.at(ctx->id("I3")).net = co_i3_net;
// I1=1 feeds carry up the chain, so no need to actually break the chain
lc->ports.at(ctx->id("I1")).net = ctx->nets.at(ctx->id("$PACKER_VCC_NET")).get();
PortRef i1_r;
i1_r.port = ctx->id("I1");
i1_r.cell = lc.get();
ctx->nets.at(ctx->id("$PACKER_VCC_NET"))->users.push_back(i1_r);
IdString name = lc->name;
ctx->cells[lc->name] = std::move(lc);
createdCells.insert(name);
return ctx->cells[name].get();
}
// Insert a logic cell to legalise a CIN->fabric connection
CellInfo *make_carry_feed_in(CellInfo *cin_cell, PortInfo &cin_port)
{
assert(cin_port.net != nullptr);
std::unique_ptr<CellInfo> lc = create_ice_cell(ctx, ctx->id("ICESTORM_LC"));
lc->params[ctx->id("CARRY_ENABLE")] = "1";
lc->params[ctx->id("CIN_CONST")] = "1";
lc->params[ctx->id("CIN_SET")] = "1";
lc->ports.at(ctx->id("I1")).net = cin_port.net;
cin_port.net->users.erase(std::remove_if(cin_port.net->users.begin(), cin_port.net->users.end(),
[cin_cell, cin_port](const PortRef &usr) {
return usr.cell == cin_cell && usr.port == cin_port.name;
}));
NetInfo *out_net = new NetInfo();
out_net->name = ctx->id(lc->name.str(ctx) + "$O");
IdString name = lc->name;
ctx->cells[lc->name] = std::move(lc);
createdCells.insert(name);
return ctx->cells[name].get();
}
Context *ctx;
std::unordered_set<IdString> rippedCells;
std::unordered_set<IdString> createdCells;
// Go from X and Y position to logic cells, setting occupied to true if a Bel is unavailable
std::vector<std::vector<std::vector<std::pair<BelId, bool>>>> logic_bels;
};
bool legalise_design(Context *ctx)
{
PlacementLegaliser lg(ctx);
return lg.legalise();
}
NEXTPNR_NAMESPACE_END
|