Playing about with placement heuristics
Signed-off-by: David Shah <davey1576@gmail.com>
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@ -181,21 +181,32 @@ static void place_cell_neighbours(Design *design, CellInfo *cell,
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{
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if (cell->bel == BelId())
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return;
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int placed_count = 0;
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const int count_thresh = 15;
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for (auto port : cell->ports) {
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NetInfo *net = port.second.net;
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if (net != nullptr) {
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if (net->users.size() > 3) // don't follow high fanout nets
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continue;
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for (auto user : net->users) {
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if (user.cell != nullptr && user.cell->bel == BelId())
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if (net->users.size() > 3)
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continue;
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if (user.cell != nullptr && user.cell->bel == BelId()) {
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place_cell(design, user.cell, cell->bel, placed_cells,
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visit_cells);
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placed_count++;
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if (placed_count > count_thresh)
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return;
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}
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}
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if (net->driver.cell != nullptr && net->driver.cell->bel == BelId())
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if (net->driver.cell != nullptr && net->driver.cell->bel == BelId()) {
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place_cell(design, net->driver.cell, cell->bel, placed_cells,
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visit_cells);
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placed_count++;
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}
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if (placed_count > count_thresh)
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return;
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}
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}
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}
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void place_design_heuristic(Design *design)
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@ -229,6 +240,7 @@ void place_design_heuristic(Design *design)
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visit_cells.push(cell);
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}
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}
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log_info("place_constraints placed %d\n", placed_cells);
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while (placed_cells < total_cells) {
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if (!visit_cells.empty()) {
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CellInfo *next = visit_cells.front();
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@ -238,8 +250,10 @@ void place_design_heuristic(Design *design)
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// Nothing to visit (netlist is split), pick the next unplaced cell
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for (auto cell : design->cells) {
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CellInfo *ci = cell.second;
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if (ci->bel == BelId())
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if (ci->bel == BelId()) {
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place_cell(design, ci, BelId(), placed_cells, visit_cells);
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break;
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}
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}
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}
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log_info("placed %d/%d\n", placed_cells, total_cells);
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