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Playing about with placement heuristics

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Signed-off-by: David Shah <davey1576@gmail.com>
This commit is contained in:
David Shah 2018-06-13 18:53:58 +02:00
parent 6b74d326d4
commit b1e08fa064
1 changed files with 19 additions and 5 deletions
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24
common/place.cc
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@ -181,21 +181,32 @@ static void place_cell_neighbours(Design *design, CellInfo *cell,
{ {
if (cell->bel == BelId()) if (cell->bel == BelId())
return; return;
int placed_count = 0;
const int count_thresh = 15;
for (auto port : cell->ports) { for (auto port : cell->ports) {
NetInfo *net = port.second.net; NetInfo *net = port.second.net;
if (net != nullptr) { if (net != nullptr) {
if (net->users.size() > 3) // don't follow high fanout nets
continue;
for (auto user : net->users) { for (auto user : net->users) {
if (user.cell != nullptr && user.cell->bel == BelId()) if (net->users.size() > 3)
continue;
if (user.cell != nullptr && user.cell->bel == BelId()) {
place_cell(design, user.cell, cell->bel, placed_cells, place_cell(design, user.cell, cell->bel, placed_cells,
visit_cells); visit_cells);
placed_count++;
if (placed_count > count_thresh)
return;
}
} }
if (net->driver.cell != nullptr && net->driver.cell->bel == BelId()) if (net->driver.cell != nullptr && net->driver.cell->bel == BelId()) {
place_cell(design, net->driver.cell, cell->bel, placed_cells, place_cell(design, net->driver.cell, cell->bel, placed_cells,
visit_cells); visit_cells);
placed_count++;
}
if (placed_count > count_thresh)
return;
} }
} }
} }
void place_design_heuristic(Design *design) void place_design_heuristic(Design *design)
@ -229,6 +240,7 @@ void place_design_heuristic(Design *design)
visit_cells.push(cell); visit_cells.push(cell);
} }
} }
log_info("place_constraints placed %d\n", placed_cells);
while (placed_cells < total_cells) { while (placed_cells < total_cells) {
if (!visit_cells.empty()) { if (!visit_cells.empty()) {
CellInfo *next = visit_cells.front(); CellInfo *next = visit_cells.front();
@ -238,8 +250,10 @@ void place_design_heuristic(Design *design)
// Nothing to visit (netlist is split), pick the next unplaced cell // Nothing to visit (netlist is split), pick the next unplaced cell
for (auto cell : design->cells) { for (auto cell : design->cells) {
CellInfo *ci = cell.second; CellInfo *ci = cell.second;
if (ci->bel == BelId()) if (ci->bel == BelId()) {
place_cell(design, ci, BelId(), placed_cells, visit_cells); place_cell(design, ci, BelId(), placed_cells, visit_cells);
break;
}
} }
} }
log_info("placed %d/%d\n", placed_cells, total_cells); log_info("placed %d/%d\n", placed_cells, total_cells);