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HeAP: Weight arcs by criticality for timing-driven placement

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Signed-off-by: David Shah <dave@ds0.me>
This commit is contained in:
David Shah 2019-01-25 13:15:36 +00:00
parent 05e9ae183d
commit 3dedc62593
1 changed files with 18 additions and 6 deletions
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24
common/placer_heap.cc
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@ -39,6 +39,7 @@
#include "placer_math.h"
#include "placer1.h"
#include "util.h"
#include "timing.h"
NEXTPNR_NAMESPACE_BEGIN
namespace {
@ -187,6 +188,10 @@ class HeAPPlacer
legal_hpwl = total_hpwl();
log_info("Legalised HPWL = %d (%s)\n", int(legal_hpwl), valid ? "valid" : "invalid");
if (ctx->timing_driven)
get_criticalities(ctx, &net_crit);
if (legal_hpwl < best_hpwl) {
best_hpwl = legal_hpwl;
stalled = 0;
@ -278,6 +283,8 @@ class HeAPPlacer
// Performance counting
double solve_time = 0, cl_time = 0, sl_time = 0;
NetCriticalityMap net_crit;
// Place cells with the BEL attribute set to constrain them
void place_constraints()
{
@ -516,9 +523,9 @@ class HeAPPlacer
template <typename Tf> void foreach_port(NetInfo *net, Tf func)
{
if (net->driver.cell != nullptr)
func(net->driver);
for (auto &user : net->users)
func(user);
func(net->driver, -1);
for (size_t i = 0; i < net->users.size(); i++)
func(net->users.at(i), i);
}
// Build the system of equations for either X or Y
@ -541,7 +548,7 @@ class HeAPPlacer
// Find the bounds of the net in this axis, and the ports that correspond to these bounds
PortRef *lbport = nullptr, *ubport = nullptr;
int lbpos = std::numeric_limits<int>::max(), ubpos = std::numeric_limits<int>::min();
foreach_port(ni, [&](PortRef &port) {
foreach_port(ni, [&](PortRef &port, int user_idx) {
int pos = cell_pos(port.cell);
if (pos < lbpos) {
lbpos = pos;
@ -573,7 +580,7 @@ class HeAPPlacer
};
// Add all relevant connections to the matrix
foreach_port(ni, [&](PortRef &port) {
foreach_port(ni, [&](PortRef &port, int user_idx) {
int this_pos = cell_pos(port.cell);
auto process_arc = [&](PortRef *other) {
if (other == &port)
@ -582,7 +589,12 @@ class HeAPPlacer
// if (o_pos == this_pos)
// return; // FIXME: or clamp to 1?
double weight = 1.0 / (ni->users.size() * std::max<double>(1, std::abs(o_pos - this_pos)));
// FIXME: add criticality to weighting
if (user_idx != -1 && net_crit.count(ni->name)) {
auto &nc = net_crit.at(ni->name);
if (user_idx < int(nc.criticality.size()))
weight *= (1.0 + 20 * std::pow(nc.criticality.at(user_idx), 2));
}
// If cell 0 is not fixed, it will stamp +w on its equation and -w on the other end's equation,
// if the other end isn't fixed