414 lines
17 KiB
C++
414 lines
17 KiB
C++
/*
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* nextpnr -- Next Generation Place and Route
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*
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* Copyright (C) 2018 David Shah <david@symbioticeda.com>
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*
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* Permission to use, copy, modify, and/or distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*
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*/
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#include "place_legaliser.h"
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#include <algorithm>
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#include <vector>
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#include "cells.h"
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#include "design_utils.h"
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#include "log.h"
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#include "place_common.h"
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#include "util.h"
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NEXTPNR_NAMESPACE_BEGIN
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struct CellChain
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{
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std::vector<CellInfo *> cells;
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float mid_x = 0, mid_y = 0;
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};
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// Generic chain finder
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template <typename F1, typename F2, typename F3>
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std::vector<CellChain> find_chains(const Context *ctx, F1 cell_type_predicate, F2 get_previous, F3 get_next,
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size_t min_length = 2)
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{
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std::set<IdString> chained;
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std::vector<CellChain> chains;
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for (auto cell : sorted(ctx->cells)) {
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if (chained.find(cell.first) != chained.end())
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continue;
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CellInfo *ci = cell.second;
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if (cell_type_predicate(ctx, ci)) {
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CellInfo *start = ci;
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CellInfo *prev_start = ci;
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while (prev_start != nullptr) {
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start = prev_start;
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prev_start = get_previous(ctx, start);
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}
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CellChain chain;
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CellInfo *end = start;
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while (end != nullptr) {
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chain.cells.push_back(end);
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end = get_next(ctx, end);
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}
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if (chain.cells.size() >= min_length) {
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chains.push_back(chain);
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for (auto c : chain.cells)
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chained.insert(c->name);
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}
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}
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}
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return chains;
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}
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static void get_chain_midpoint(const Context *ctx, const CellChain &chain, float &x, float &y)
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{
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float total_x = 0, total_y = 0;
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int N = 0;
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for (auto cell : chain.cells) {
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if (cell->bel == BelId())
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continue;
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int bel_x, bel_y;
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bool bel_gb;
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ctx->estimatePosition(cell->bel, bel_x, bel_y, bel_gb);
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total_x += bel_x;
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total_y += bel_y;
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N++;
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}
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assert(N > 0);
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x = total_x / N;
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y = total_y / N;
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}
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class PlacementLegaliser
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{
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public:
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PlacementLegaliser(Context *ctx) : ctx(ctx){};
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bool legalise()
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{
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log_info("Legalising design..\n");
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init_logic_cells();
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bool legalised_carries = legalise_carries();
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if (!legalised_carries && !ctx->force)
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return false;
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bool replaced_cells = replace_cells();
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return legalised_carries && replaced_cells;
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}
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private:
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void init_logic_cells()
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{
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for (auto bel : ctx->getBels()) {
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// Initialise the logic bels vector with unavailable invalid bels, dimensions [0..width][0..height[0..7]
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logic_bels.resize(ctx->chip_info->width + 1,
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std::vector<std::vector<std::pair<BelId, bool>>>(
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ctx->chip_info->height + 1,
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std::vector<std::pair<BelId, bool>>(8, std::make_pair(BelId(), true))));
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if (ctx->getBelType(bel) == TYPE_ICESTORM_LC) {
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// Using the non-standard API here to get (x, y, z) rather than just (x, y)
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auto bi = ctx->chip_info->bel_data[bel.index];
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int x = bi.x, y = bi.y, z = bi.z;
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IdString cell = ctx->getBoundBelCell(bel);
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if (cell != IdString() && ctx->cells.at(cell)->belStrength >= STRENGTH_FIXED)
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logic_bels.at(x).at(y).at(z) = std::make_pair(bel, true); // locked out of use
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else
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logic_bels.at(x).at(y).at(z) = std::make_pair(bel, false); // available
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}
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}
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}
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bool legalise_carries()
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{
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std::vector<CellChain> carry_chains = find_chains(
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ctx, is_lc,
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[](const Context *ctx, const CellInfo *cell) {
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CellInfo *carry_prev =
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net_driven_by(ctx, cell->ports.at(ctx->id("CIN")).net, is_lc, ctx->id("COUT"));
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if (carry_prev != nullptr)
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return carry_prev;
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CellInfo *i3_prev = net_driven_by(ctx, cell->ports.at(ctx->id("I3")).net, is_lc, ctx->id("COUT"));
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if (i3_prev != nullptr)
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return i3_prev;
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return (CellInfo *)nullptr;
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},
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[](const Context *ctx, const CellInfo *cell) {
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CellInfo *carry_next =
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net_only_drives(ctx, cell->ports.at(ctx->id("COUT")).net, is_lc, ctx->id("CIN"), false);
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if (carry_next != nullptr)
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return carry_next;
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CellInfo *i3_next =
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net_only_drives(ctx, cell->ports.at(ctx->id("COUT")).net, is_lc, ctx->id("I3"), false);
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if (i3_next != nullptr)
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return i3_next;
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return (CellInfo *)nullptr;
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});
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bool success = true;
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// Find midpoints for all chains, before we start tearing them up
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std::vector<CellChain> all_chains;
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for (auto &base_chain : carry_chains) {
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if (ctx->verbose) {
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log_info("Found carry chain: \n");
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for (auto entry : base_chain.cells)
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log_info(" %s\n", entry->name.c_str(ctx));
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log_info("\n");
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}
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std::vector<CellChain> split_chains = split_carry_chain(base_chain);
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for (auto &chain : split_chains) {
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get_chain_midpoint(ctx, chain, chain.mid_x, chain.mid_y);
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all_chains.push_back(chain);
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}
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}
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// Actual chain placement
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for (auto &chain : all_chains) {
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if (ctx->verbose)
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log_info("Placing carry chain starting at '%s'\n", chain.cells.front()->name.c_str(ctx));
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float base_x = chain.mid_x, base_y = chain.mid_y - (chain.cells.size() / 16.0f);
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// Find Bel meeting requirements closest to the target base, returning location as <x, y, z>
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auto chain_origin_bel = find_closest_bel(base_x, base_y, int(chain.cells.size()));
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int place_x = std::get<0>(chain_origin_bel), place_y = std::get<1>(chain_origin_bel),
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place_z = std::get<2>(chain_origin_bel);
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if (place_x == -1) {
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if (ctx->force) {
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log_warning("failed to place carry chain, starting with cell '%s', length %d\n",
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chain.cells.front()->name.c_str(ctx), int(chain.cells.size()));
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success = false;
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continue;
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} else {
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log_error("failed to place carry chain, starting with cell '%s', length %d\n",
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chain.cells.front()->name.c_str(ctx), int(chain.cells.size()));
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}
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}
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// Place carry chain
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for (int i = 0; i < int(chain.cells.size()); i++) {
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int target_z = place_y * 8 + place_z + i;
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place_lc(chain.cells.at(i), place_x, target_z / 8, target_z % 8);
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if (ctx->verbose)
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log_info(" Cell '%s' placed at (%d, %d, %d)\n", chain.cells.at(i)->name.c_str(ctx), place_x,
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target_z / 8, target_z % 8);
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}
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}
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return success;
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}
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// Find Bel closest to a location, meeting chain requirements
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std::tuple<int, int, int> find_closest_bel(float target_x, float target_y, int chain_size)
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{
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std::tuple<int, int, int> best_origin = std::make_tuple(-1, -1, -1);
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float smallest_distance = std::numeric_limits<float>::infinity();
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int width = ctx->chip_info->width, height = ctx->chip_info->height;
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// Slow, should radiate outwards from target position - TODO
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for (int x = 1; x < width; x++) {
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for (int y = 1; y < (height - (chain_size / 8)); y++) {
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bool valid = true;
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for (int k = 0; k < chain_size; k++) {
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if (logic_bels.at(x).at(y + k / 8).at(k % 8).second) {
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valid = false;
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break;
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}
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}
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if (valid) {
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float distance = (x - target_x) * (x - target_x) + (y - target_y) * (y - target_y);
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if (distance < smallest_distance) {
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smallest_distance = distance;
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best_origin = std::make_tuple(x, y, 0);
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}
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}
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}
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}
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return best_origin;
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}
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// Split a carry chain into multiple legal chains
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std::vector<CellChain> split_carry_chain(CellChain &carryc)
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{
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bool start_of_chain = true;
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std::vector<CellChain> chains;
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std::vector<const CellInfo *> tile;
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const int max_length = (ctx->chip_info->height - 2) * 8 - 2;
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auto curr_cell = carryc.cells.begin();
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while (curr_cell != carryc.cells.end()) {
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CellInfo *cell = *curr_cell;
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if (tile.size() >= 8) {
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tile.clear();
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}
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if (start_of_chain) {
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tile.clear();
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chains.emplace_back();
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start_of_chain = false;
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if (cell->ports.at(ctx->id("CIN")).net) {
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// CIN is not constant and not part of a chain. Must feed in from fabric
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CellInfo *feedin = make_carry_feed_in(cell, cell->ports.at(ctx->id("CIN")));
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chains.back().cells.push_back(feedin);
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tile.push_back(feedin);
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}
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}
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tile.push_back(cell);
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chains.back().cells.push_back(cell);
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bool split_chain = (!ctx->logicCellsCompatible(tile)) || (int(chains.back().cells.size()) > max_length);
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if (split_chain) {
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CellInfo *passout = make_carry_pass_out(cell->ports.at(ctx->id("COUT")));
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tile.pop_back();
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chains.back().cells.back() = passout;
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start_of_chain = true;
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} else {
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NetInfo *carry_net = cell->ports.at(ctx->id("COUT")).net;
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bool at_end = (curr_cell == carryc.cells.end() - 1);
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if (carry_net != nullptr && (carry_net->users.size() > 1 || at_end)) {
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if (carry_net->users.size() > 2 ||
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(net_only_drives(ctx, carry_net, is_lc, ctx->id("I3"), false) !=
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net_only_drives(ctx, carry_net, is_lc, ctx->id("CIN"), false)) ||
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(at_end && !net_only_drives(ctx, carry_net, is_lc, ctx->id("I3"), true))) {
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CellInfo *passout = make_carry_pass_out(cell->ports.at(ctx->id("COUT")));
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chains.back().cells.push_back(passout);
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tile.push_back(passout);
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}
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}
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++curr_cell;
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}
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}
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return chains;
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}
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// Place a logic cell at a given grid location, handling rip-up etc
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void place_lc(CellInfo *cell, int x, int y, int z)
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{
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auto &loc = logic_bels.at(x).at(y).at(z);
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assert(!loc.second);
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BelId bel = loc.first;
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// Check if there is a cell presently at the location, which we will need to rip up
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IdString existing = ctx->getBoundBelCell(bel);
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if (existing != IdString()) {
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// TODO: keep track of the previous position of the ripped up cell, as a hint
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rippedCells.insert(existing);
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ctx->unbindBel(bel);
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}
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if (cell->bel != BelId()) {
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ctx->unbindBel(cell->bel);
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}
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ctx->bindBel(bel, cell->name, STRENGTH_LOCKED);
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rippedCells.erase(cell->name); // If cell was ripped up previously, no need to re-place
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loc.second = true; // Bel is now unavailable for further use
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}
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// Insert a logic cell to legalise a COUT->fabric connection
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CellInfo *make_carry_pass_out(PortInfo &cout_port)
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{
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assert(cout_port.net != nullptr);
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std::unique_ptr<CellInfo> lc = create_ice_cell(ctx, ctx->id("ICESTORM_LC"));
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lc->params[ctx->id("LUT_INIT")] = "65280"; // 0xff00: O = I3
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lc->params[ctx->id("CARRY_ENABLE")] = "1";
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lc->ports.at(ctx->id("O")).net = cout_port.net;
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std::unique_ptr<NetInfo> co_i3_net(new NetInfo());
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co_i3_net->name = ctx->id(lc->name.str(ctx) + "$I3");
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co_i3_net->driver = cout_port.net->driver;
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PortRef i3_r;
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i3_r.port = ctx->id("I3");
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i3_r.cell = lc.get();
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co_i3_net->users.push_back(i3_r);
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PortRef o_r;
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o_r.port = ctx->id("O");
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o_r.cell = lc.get();
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cout_port.net->driver = o_r;
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lc->ports.at(ctx->id("I3")).net = co_i3_net.get();
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cout_port.net = co_i3_net.get();
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// I1=1 feeds carry up the chain, so no need to actually break the chain
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lc->ports.at(ctx->id("I1")).net = ctx->nets.at(ctx->id("$PACKER_VCC_NET")).get();
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PortRef i1_r;
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i1_r.port = ctx->id("I1");
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i1_r.cell = lc.get();
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ctx->nets.at(ctx->id("$PACKER_VCC_NET"))->users.push_back(i1_r);
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IdString co_i3_name = co_i3_net->name;
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assert(ctx->nets.find(co_i3_name) == ctx->nets.end());
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ctx->nets[co_i3_name] = std::move(co_i3_net);
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IdString name = lc->name;
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ctx->cells[lc->name] = std::move(lc);
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createdCells.insert(name);
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return ctx->cells[name].get();
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}
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// Insert a logic cell to legalise a CIN->fabric connection
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CellInfo *make_carry_feed_in(CellInfo *cin_cell, PortInfo &cin_port)
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{
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assert(cin_port.net != nullptr);
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std::unique_ptr<CellInfo> lc = create_ice_cell(ctx, ctx->id("ICESTORM_LC"));
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lc->params[ctx->id("CARRY_ENABLE")] = "1";
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lc->params[ctx->id("CIN_CONST")] = "1";
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lc->params[ctx->id("CIN_SET")] = "1";
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lc->ports.at(ctx->id("I1")).net = cin_port.net;
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cin_port.net->users.erase(std::remove_if(cin_port.net->users.begin(), cin_port.net->users.end(),
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[cin_cell, cin_port](const PortRef &usr) {
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return usr.cell == cin_cell && usr.port == cin_port.name;
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}));
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PortRef i1_ref;
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i1_ref.cell = lc.get();
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i1_ref.port = ctx->id("I1");
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lc->ports.at(ctx->id("I1")).net->users.push_back(i1_ref);
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std::unique_ptr<NetInfo> out_net(new NetInfo());
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out_net->name = ctx->id(lc->name.str(ctx) + "$O");
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PortRef drv_ref;
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drv_ref.port = ctx->id("COUT");
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drv_ref.cell = lc.get();
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out_net->driver = drv_ref;
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lc->ports.at(ctx->id("COUT")).net = out_net.get();
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PortRef usr_ref;
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usr_ref.port = cin_port.name;
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usr_ref.cell = cin_cell;
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out_net->users.push_back(usr_ref);
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cin_cell->ports.at(cin_port.name).net = out_net.get();
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IdString out_net_name = out_net->name;
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assert(ctx->nets.find(out_net_name) == ctx->nets.end());
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ctx->nets[out_net_name] = std::move(out_net);
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IdString name = lc->name;
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ctx->cells[lc->name] = std::move(lc);
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createdCells.insert(name);
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return ctx->cells[name].get();
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}
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// Replace ripped-up cells
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bool replace_cells()
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{
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bool success = true;
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for (auto cell : sorted(rippedCells)) {
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CellInfo *ci = ctx->cells.at(cell).get();
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bool placed = place_single_cell(ctx, ci, true);
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if (!placed) {
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if (ctx->force) {
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log_warning("failed to place cell '%s' of type '%s'\n", cell.c_str(ctx), ci->type.c_str(ctx));
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success = false;
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} else {
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log_error("failed to place cell '%s' of type '%s'\n", cell.c_str(ctx), ci->type.c_str(ctx));
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}
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}
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}
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return success;
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}
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Context *ctx;
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std::unordered_set<IdString> rippedCells;
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std::unordered_set<IdString> createdCells;
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// Go from X and Y position to logic cells, setting occupied to true if a Bel is unavailable
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std::vector<std::vector<std::vector<std::pair<BelId, bool>>>> logic_bels;
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};
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bool legalise_design(Context *ctx)
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{
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PlacementLegaliser lg(ctx);
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return lg.legalise();
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}
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NEXTPNR_NAMESPACE_END
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