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-rw-r--r--common/nextpnr.cc22
-rw-r--r--common/nextpnr.h8
-rw-r--r--common/place_common.cc8
-rw-r--r--common/place_common.h3
-rw-r--r--common/placer1.cc21
-rw-r--r--common/placer_heap.cc67
6 files changed, 88 insertions, 41 deletions
diff --git a/common/nextpnr.cc b/common/nextpnr.cc
index 9a73affc..dd1ebc59 100644
--- a/common/nextpnr.cc
+++ b/common/nextpnr.cc
@@ -223,6 +223,28 @@ void CellInfo::unsetParam(IdString name) { params.erase(name); }
void CellInfo::setAttr(IdString name, Property value) { attrs[name] = value; }
void CellInfo::unsetAttr(IdString name) { attrs.erase(name); }
+bool CellInfo::isConstrained(bool include_abs_z_constr) const
+{
+ return constr_parent != nullptr || !constr_children.empty() || (include_abs_z_constr && constr_abs_z);
+}
+
+bool CellInfo::testRegion(BelId bel) const
+{
+ return region == nullptr || !region->constr_bels || region->bels.count(bel);
+}
+Loc CellInfo::getConstrainedLoc(Loc parent_loc) const
+{
+ NPNR_ASSERT(constr_parent != nullptr);
+ Loc cloc = parent_loc;
+ if (constr_x != UNCONSTR)
+ cloc.x += constr_x;
+ if (constr_y != UNCONSTR)
+ cloc.y += constr_y;
+ if (constr_z != UNCONSTR)
+ cloc.z = constr_abs_z ? constr_z : (parent_loc.z + constr_z);
+ return cloc;
+}
+
std::string Property::to_string() const
{
if (is_string) {
diff --git a/common/nextpnr.h b/common/nextpnr.h
index c2fe5192..ed227fb6 100644
--- a/common/nextpnr.h
+++ b/common/nextpnr.h
@@ -664,6 +664,14 @@ struct CellInfo : ArchCellInfo
void unsetParam(IdString name);
void setAttr(IdString name, Property value);
void unsetAttr(IdString name);
+
+ // return true if the cell has placement constraints (optionally excluding the case where the only case is an
+ // absolute z constraint)
+ bool isConstrained(bool include_abs_z_constr = true) const;
+ // check whether a bel complies with the cell's region constraint
+ bool testRegion(BelId bel) const;
+ // get the constrained location for this cell given a provisional location for its parent
+ Loc getConstrainedLoc(Loc parent_loc) const;
};
enum TimingPortClass
diff --git a/common/place_common.cc b/common/place_common.cc
index e5b48ffb..31b93420 100644
--- a/common/place_common.cc
+++ b/common/place_common.cc
@@ -536,12 +536,4 @@ int get_constraints_distance(const Context *ctx, const CellInfo *cell)
return dist;
}
-bool check_cell_bel_region(const CellInfo *cell, BelId bel)
-{
- if (cell->region != nullptr && cell->region->constr_bels && !cell->region->bels.count(bel))
- return false;
- else
- return true;
-}
-
NEXTPNR_NAMESPACE_END
diff --git a/common/place_common.h b/common/place_common.h
index fa5ce4c2..434233fd 100644
--- a/common/place_common.h
+++ b/common/place_common.h
@@ -50,9 +50,6 @@ bool legalise_relative_constraints(Context *ctx);
// Get the total distance from satisfied constraints for a cell
int get_constraints_distance(const Context *ctx, const CellInfo *cell);
-// Check that a Bel is within the region for a cell
-bool check_cell_bel_region(const CellInfo *cell, BelId bel);
-
NEXTPNR_NAMESPACE_END
#endif
diff --git a/common/placer1.cc b/common/placer1.cc
index 270430e9..837010fe 100644
--- a/common/placer1.cc
+++ b/common/placer1.cc
@@ -504,12 +504,12 @@ class SAPlacer
{
static const double epsilon = 1e-20;
moveChange.reset(this);
- if (!require_legal && is_constrained(cell))
+ if (!require_legal && cell->isConstrained(false))
return false;
BelId oldBel = cell->bel;
CellInfo *other_cell = ctx->getBoundBelCell(newBel);
if (!require_legal && other_cell != nullptr &&
- (is_constrained(other_cell) || other_cell->belStrength > STRENGTH_WEAK)) {
+ (other_cell->isConstrained(false) || other_cell->belStrength > STRENGTH_WEAK)) {
return false;
}
int old_dist = get_constraints_distance(ctx, cell);
@@ -589,11 +589,6 @@ class SAPlacer
return false;
}
- inline bool is_constrained(CellInfo *cell)
- {
- return cell->constr_parent != nullptr || !cell->constr_children.empty();
- }
-
// Swap the Bel of a cell with another, return the original location
BelId swap_cell_bels(CellInfo *cell, BelId newBel)
{
@@ -605,9 +600,9 @@ class SAPlacer
if (bound != nullptr)
ctx->unbindBel(newBel);
ctx->unbindBel(oldBel);
- ctx->bindBel(newBel, cell, is_constrained(cell) ? STRENGTH_STRONG : STRENGTH_WEAK);
+ ctx->bindBel(newBel, cell, cell->isConstrained(false) ? STRENGTH_STRONG : STRENGTH_WEAK);
if (bound != nullptr) {
- ctx->bindBel(oldBel, bound, is_constrained(bound) ? STRENGTH_STRONG : STRENGTH_WEAK);
+ ctx->bindBel(oldBel, bound, bound->isConstrained(false) ? STRENGTH_STRONG : STRENGTH_WEAK);
if (cfg.netShareWeight > 0)
update_nets_by_tile(bound, ctx->getBelLocation(newBel), ctx->getBelLocation(oldBel));
}
@@ -658,7 +653,7 @@ class SAPlacer
// We don't consider swapping chains with other chains, at least for the time being - unless it is
// part of this chain
if (bound != nullptr && !cells.count(bound->name) &&
- (bound->belStrength >= STRENGTH_STRONG || is_constrained(bound)))
+ (bound->belStrength >= STRENGTH_STRONG || bound->isConstrained(false)))
return false;
dest_bels.emplace_back(std::make_pair(cr.first, targetBel));
}
@@ -676,12 +671,12 @@ class SAPlacer
add_move_cell(moveChange, bound, db.second);
}
for (const auto &mm : moves_made) {
- if (!ctx->isBelLocationValid(mm.first->bel) || !check_cell_bel_region(mm.first, mm.first->bel))
+ if (!ctx->isBelLocationValid(mm.first->bel) || !mm.first->testRegion(mm.first->bel))
goto swap_fail;
if (!ctx->isBelLocationValid(mm.second))
goto swap_fail;
CellInfo *bound = ctx->getBoundBelCell(mm.second);
- if (bound && !check_cell_bel_region(bound, bound->bel))
+ if (bound && !bound->testRegion(bound->bel))
goto swap_fail;
}
compute_cost_changes(moveChange);
@@ -752,7 +747,7 @@ class SAPlacer
if (loc.z != force_z)
continue;
}
- if (!check_cell_bel_region(cell, bel))
+ if (!cell->testRegion(bel))
continue;
if (locked_bels.find(bel) != locked_bels.end())
continue;
diff --git a/common/placer_heap.cc b/common/placer_heap.cc
index 92caaf09..8a3b427f 100644
--- a/common/placer_heap.cc
+++ b/common/placer_heap.cc
@@ -222,6 +222,7 @@ class HeAPPlacer
// Heuristic: don't bother with threading below a certain size
auto solve_startt = std::chrono::high_resolution_clock::now();
+ // Build the connectivity matrix and run the solver; multithreaded between x and y axes if applicable
#ifndef NPNR_DISABLE_THREADS
if (solve_cells.size() >= 500) {
boost::thread xaxis([&]() { build_solve_direction(false, (iter == 0) ? -1 : iter); });
@@ -240,6 +241,7 @@ class HeAPPlacer
update_all_chains();
+ // Run the spreader
for (const auto &group : cfg.cellGroups)
CutSpreader(this, group).run();
@@ -248,6 +250,7 @@ class HeAPPlacer
[type](const std::unordered_set<BelBucketId> &grp) { return !grp.count(type); }))
CutSpreader(this, {type}).run();
+ // Run strict legalisation to find a valid bel for all cells
update_all_chains();
spread_hpwl = total_hpwl();
legalise_placement_strict(true);
@@ -263,6 +266,7 @@ class HeAPPlacer
std::chrono::duration<double>(run_stopt - run_startt).count());
}
+ // Update timing weights
if (cfg.timing_driven)
get_criticalities(ctx, &net_crit);
@@ -851,6 +855,8 @@ class HeAPPlacer
log_error("Unable to find legal placement for cell '%s', check constraints and utilisation.\n",
ctx->nameOf(ci));
+ // Determine a search radius around the solver location (which increases over time) that is clamped to
+ // the region constraint for the cell (if applicable)
int rx = radius, ry = radius;
if (ci->region != nullptr) {
@@ -864,14 +870,18 @@ class HeAPPlacer
1);
}
+ // Pick a random X and Y location within our search radius
int nx = ctx->rng(2 * rx + 1) + std::max(cell_locs.at(ci->name).x - rx, 0);
int ny = ctx->rng(2 * ry + 1) + std::max(cell_locs.at(ci->name).y - ry, 0);
iter++;
iter_at_radius++;
if (iter >= (10 * (radius + 1))) {
+ // No luck yet, increase radius
radius = std::min(std::max(max_x, max_y), radius + 1);
while (radius < std::max(max_x, max_y)) {
+ // Keep increasing the radius until it will actually increase the number of cells we are
+ // checking (e.g. BRAM and DSP will not be in all cols/rows), so we don't waste effort
for (int x = std::max(0, cell_locs.at(ci->name).x - radius);
x <= std::min(max_x, cell_locs.at(ci->name).x + radius); x++) {
if (x >= int(fb->size()))
@@ -890,6 +900,8 @@ class HeAPPlacer
iter_at_radius = 0;
iter = 0;
}
+ // If our randomly chosen cooridnate is out of bounds; or points to a tile with no relevant bels; ignore
+ // it
if (nx < 0 || nx > max_x)
continue;
if (ny < 0 || ny > max_y)
@@ -902,8 +914,11 @@ class HeAPPlacer
if (fb->at(nx).at(ny).empty())
continue;
+ // The number of attempts to find a location to try
int need_to_explore = 2 * radius;
+ // If we have found at least one legal location; and made enough attempts; assume it's good enough and
+ // finish
if (iter_at_radius >= need_to_explore && bestBel != BelId()) {
CellInfo *bound = ctx->getBoundBelCell(bestBel);
if (bound != nullptr) {
@@ -919,27 +934,37 @@ class HeAPPlacer
}
if (ci->constr_children.empty() && !ci->constr_abs_z) {
+ // The case where we have no relative constraints
for (auto sz : fb->at(nx).at(ny)) {
- if (ci->region != nullptr && ci->region->constr_bels && !ci->region->bels.count(sz))
+ // Look through all bels in this tile; checking region constraint if applicable
+ if (!ci->testRegion(sz))
continue;
+ // Prefer available bels; unless we are dealing with a wide radius (e.g. difficult control sets)
+ // or occasionally trigger a tiebreaker
if (ctx->checkBelAvail(sz) || (radius > ripup_radius || ctx->rng(20000) < 10)) {
CellInfo *bound = ctx->getBoundBelCell(sz);
if (bound != nullptr) {
- if (bound->constr_parent != nullptr || !bound->constr_children.empty() ||
- bound->constr_abs_z)
+ // Only rip up cells without constraints
+ if (bound->isConstrained())
continue;
ctx->unbindBel(bound->bel);
}
+ // Provisionally bind the bel
ctx->bindBel(sz, ci, STRENGTH_WEAK);
if (require_validity && !ctx->isBelLocationValid(sz)) {
+ // New location is not legal; unbind the cell (and rebind the cell we ripped up if
+ // applicable)
ctx->unbindBel(sz);
if (bound != nullptr)
ctx->bindBel(sz, bound, STRENGTH_WEAK);
} else if (iter_at_radius < need_to_explore) {
+ // It's legal, but we haven't tried enough locations yet
ctx->unbindBel(sz);
if (bound != nullptr)
ctx->bindBel(sz, bound, STRENGTH_WEAK);
int input_len = 0;
+ // Compute a fast input wirelength metric at this bel; and save if better than our last
+ // try
for (auto &port : ci->ports) {
auto &p = port.second;
if (p.type != PORT_IN || p.net == nullptr || p.net->driver.cell == nullptr)
@@ -958,6 +983,7 @@ class HeAPPlacer
}
break;
} else {
+ // It's legal, and we've tried enough. Finish.
if (bound != nullptr)
remaining.emplace(chain_size[bound->name], bound->name);
Loc loc = ctx->getBelLocation(sz);
@@ -969,44 +995,49 @@ class HeAPPlacer
}
}
} else {
+ // We do have relative constraints
for (auto sz : fb->at(nx).at(ny)) {
Loc loc = ctx->getBelLocation(sz);
+ // Check that the absolute-z constraint is satisfied if applicable
if (ci->constr_abs_z && loc.z != ci->constr_z)
continue;
+ // List of cells and their destination
std::vector<std::pair<CellInfo *, BelId>> targets;
+ // List of bels we placed things at; and the cell that was there before if applicable
std::vector<std::pair<BelId, CellInfo *>> swaps_made;
+ // List of (cell, new location) pairs to check
std::queue<std::pair<CellInfo *, Loc>> visit;
+ // FIXME: this approach of having a visit queue is designed to deal with recursively chained
+ // cells. But is this a case we really want to care about given the complexity it adds? Start by
+ // considering the root cell at the root location
visit.emplace(ci, loc);
while (!visit.empty()) {
CellInfo *vc = visit.front().first;
NPNR_ASSERT(vc->bel == BelId());
Loc ploc = visit.front().second;
visit.pop();
+ // Get the bel we're going to place this cell at
BelId target = ctx->getBelByLocation(ploc);
- if (vc->region != nullptr && vc->region->constr_bels && !vc->region->bels.count(target))
+ // Check it satisfies the region constraint if applicable
+ if (!vc->testRegion(target))
goto fail;
CellInfo *bound;
+ // Check that the target bel exists and is of a suitable type
if (target == BelId() || !ctx->isValidBelForCellType(vc->type, target))
goto fail;
bound = ctx->getBoundBelCell(target);
- // Chains cannot overlap
+ // Chains cannot overlap; so if we have to ripup a cell make sure it isn't part of a chain
if (bound != nullptr)
- if (bound->constr_z != bound->UNCONSTR || bound->constr_parent != nullptr ||
- !bound->constr_children.empty() || bound->belStrength > STRENGTH_WEAK)
+ if (bound->isConstrained() || bound->belStrength > STRENGTH_WEAK)
goto fail;
targets.emplace_back(vc, target);
for (auto child : vc->constr_children) {
- Loc cloc = ploc;
- if (child->constr_x != child->UNCONSTR)
- cloc.x += child->constr_x;
- if (child->constr_y != child->UNCONSTR)
- cloc.y += child->constr_y;
- if (child->constr_z != child->UNCONSTR)
- cloc.z = child->constr_abs_z ? child->constr_z : (ploc.z + child->constr_z);
- visit.emplace(child, cloc);
+ // For all the constrained children; compute the location we need to place them at and
+ // add them to the queue
+ visit.emplace(child, child->getConstrainedLoc(ploc));
}
}
-
+ // Actually perform the move; keeping track of the moves we make so we can revert them if needed
for (auto &target : targets) {
CellInfo *bound = ctx->getBoundBelCell(target.second);
if (bound != nullptr)
@@ -1014,7 +1045,7 @@ class HeAPPlacer
ctx->bindBel(target.second, target.first, STRENGTH_STRONG);
swaps_made.emplace_back(target.second, bound);
}
-
+ // Check that the move we have made is legal
for (auto &sm : swaps_made) {
if (!ctx->isBelLocationValid(sm.first))
goto fail;
@@ -1022,6 +1053,7 @@ class HeAPPlacer
if (false) {
fail:
+ // If the move turned out to be illegal; revert all the moves we made
for (auto &swap : swaps_made) {
ctx->unbindBel(swap.first);
if (swap.second != nullptr)
@@ -1036,6 +1068,7 @@ class HeAPPlacer
// log_info("%s %d %d %d\n", target.first->name.c_str(ctx), loc.x, loc.y, loc.z);
}
for (auto &swap : swaps_made) {
+ // Where we have ripped up cells; add them to the queue
if (swap.second != nullptr)
remaining.emplace(chain_size[swap.second->name], swap.second->name);
}
generated by cgit v1.2.3 (git 2.25.1) at 2025-02-13 13:14:41 +0000