netlist: Add PseudoCell API

When implementing concepts such as partition pins or deliberately split
nets, there's a need for something that looks like a cell (starts/ends
routing with pins on nets, has timing data) but isn't mapped to a fixed
bel in the architecture, but instead can have pin mappings defined at
runtime.

The PseudoCell allows this by providing an alternate, virtual-function
based API for such cells. When a cell has `pseudo_cell` used, instead of
calling functions such as getBelPinWire, getBelLocation or getCellDelay
in the Arch API; such data is provided by the cell itself, fully
flexible at runtime regardless of arch, via methods on the PseudoCell
implementation.

5 files changed, 50 insertions, 14 deletions

diff --git a/common/place/detail_place_core.cc b/common/place/detail_place_core.cc
index 7e629f24..18118fc8 100644
--- a/common/place/detail_place_core.cc
+++ b/common/place/detail_place_core.cc
@@ -37,6 +37,8 @@ PlacePartition::PlacePartition(Context *ctx)
     x1 = 0;
     y1 = 0;
     for (auto &cell : ctx->cells) {
+        if (cell.second->isPseudo())
+            continue;
         Loc l = ctx->getBelLocation(cell.second->bel);
         x0 = std::min(x0, l.x);
         x1 = std::max(x1, l.x);
@@ -110,6 +112,8 @@ NetBB NetBB::compute(const Context *ctx, const NetInfo *net, const dict<IdString
     if (!net->driver.cell)
         return result;
     auto bel_loc = [&](const CellInfo *cell) {
+        if (cell->isPseudo())
+            return cell->getLocation();
         BelId bel = cell2bel ? cell2bel->at(cell->name) : cell->bel;
         return ctx->getBelLocation(bel);
     };
@@ -176,10 +180,12 @@ void DetailPlacerThreadState::set_partition(const PlacePartition &part)
     // Set up the original cell-bel map for all nets inside the thread
     local_cell2bel.clear();
     for (NetInfo *net : thread_nets) {
-        if (net->driver.cell)
+        if (net->driver.cell && !net->driver.cell->isPseudo())
             local_cell2bel[net->driver.cell->name] = net->driver.cell->bel;
-        for (auto &usr : net->users)
-            local_cell2bel[usr.cell->name] = usr.cell->bel;
+        for (auto &usr : net->users) {
+            if (!usr.cell->isPseudo())
+                local_cell2bel[usr.cell->name] = usr.cell->bel;
+        }
     }
 }
 
diff --git a/common/place/parallel_refine.cc b/common/place/parallel_refine.cc
index de71b8e0..0fb99be5 100644
--- a/common/place/parallel_refine.cc
+++ b/common/place/parallel_refine.cc
@@ -390,6 +390,8 @@ struct ParallelRefine
         // Setup fast bels map
         pool<IdString> cell_types_in_use;
         for (auto &cell : ctx->cells) {
+            if (cell.second->isPseudo())
+                continue;
             IdString cell_type = cell.second->type;
             cell_types_in_use.insert(cell_type);
             if (cell.second->cluster != ClusterId())
diff --git a/common/place/place_common.cc b/common/place/place_common.cc
index e03fca55..c2fc3b7d 100644
--- a/common/place/place_common.cc
+++ b/common/place/place_common.cc
@@ -293,6 +293,8 @@ class ConstraintLegaliseWorker
     {
         if (cell->cluster != ClusterId() && ctx->getClusterRootCell(cell->cluster) != cell)
             return true; // Only process chain roots
+        if (cell->isPseudo())
+            return true;
         if (constraints_satisfied(cell)) {
             if (cell->cluster != ClusterId())
                 lockdown_chain(cell);
@@ -415,7 +417,7 @@ class ConstraintLegaliseWorker
     {
         log_info("Legalising relative constraints...\n");
         for (auto &cell : ctx->cells) {
-            oldLocations[cell.first] = ctx->getBelLocation(cell.second->bel);
+            oldLocations[cell.first] = cell.second->getLocation();
         }
         for (auto &cell : ctx->cells) {
             bool res = legalise_cell(cell.second.get());
@@ -448,6 +450,8 @@ bool legalise_relative_constraints(Context *ctx) { return ConstraintLegaliseWork
 int get_constraints_distance(const Context *ctx, const CellInfo *cell)
 {
     int dist = 0;
+    if (cell->isPseudo())
+        return 0;
     if (cell->bel == BelId())
         return 100000;
     Loc loc = ctx->getBelLocation(cell->bel);
diff --git a/common/place/placer1.cc b/common/place/placer1.cc
index a6ba3895..23264ce2 100644
--- a/common/place/placer1.cc
+++ b/common/place/placer1.cc
@@ -76,6 +76,8 @@ class SAPlacer
 
         pool<IdString> cell_types_in_use;
         for (auto &cell : ctx->cells) {
+            if (cell.second->isPseudo())
+                continue;
             IdString cell_type = cell.second->type;
             cell_types_in_use.insert(cell_type);
         }
@@ -120,7 +122,7 @@ class SAPlacer
         }
         for (auto &cell : ctx->cells) {
             CellInfo *ci = cell.second.get();
-            if (ci->cluster == ClusterId())
+            if (ci->isPseudo() || ci->cluster == ClusterId())
                 continue;
             cluster2cell[ci->cluster].push_back(ci);
         }
@@ -145,6 +147,8 @@ class SAPlacer
             // Initial constraints placer
             for (auto &cell_entry : ctx->cells) {
                 CellInfo *cell = cell_entry.second.get();
+                if (cell->isPseudo())
+                    continue;
                 auto loc = cell->attrs.find(ctx->id("BEL"));
                 if (loc != cell->attrs.end()) {
                     std::string loc_name = loc->second.as_string();
@@ -187,7 +191,7 @@ class SAPlacer
 
             for (auto &cell : ctx->cells) {
                 CellInfo *ci = cell.second.get();
-                if (ci->bel == BelId()) {
+                if (!ci->isPseudo() && (ci->bel == BelId())) {
                     autoplaced.push_back(cell.second.get());
                 }
             }
@@ -217,7 +221,7 @@ class SAPlacer
         } else {
             for (auto &cell : ctx->cells) {
                 CellInfo *ci = cell.second.get();
-                if (ci->belStrength > STRENGTH_STRONG) {
+                if (ci->isPseudo() || ci->belStrength > STRENGTH_STRONG) {
                     continue;
                 } else if (ci->cluster != ClusterId()) {
                     if (ctx->getClusterRootCell(ci->cluster) == ci)
@@ -353,6 +357,8 @@ class SAPlacer
                     autoplaced.clear();
                     chain_basis.clear();
                     for (auto &cell : ctx->cells) {
+                        if (cell.second->isPseudo())
+                            continue;
                         if (cell.second->belStrength <= STRENGTH_STRONG && cell.second->cluster != ClusterId() &&
                             ctx->getClusterRootCell(cell.second->cluster) == cell.second.get())
                             chain_basis.push_back(cell.second.get());
@@ -814,7 +820,7 @@ class SAPlacer
     {
         BoundingBox bb;
         NPNR_ASSERT(net->driver.cell != nullptr);
-        Loc dloc = ctx->getBelLocation(net->driver.cell->bel);
+        Loc dloc = net->driver.cell->getLocation();
         bb.x0 = dloc.x;
         bb.x1 = dloc.x;
         bb.y0 = dloc.y;
@@ -824,9 +830,9 @@ class SAPlacer
         bb.ny0 = 1;
         bb.ny1 = 1;
         for (auto user : net->users) {
-            if (user.cell->bel == BelId())
+            if (!user.cell->isPseudo() && user.cell->bel == BelId())
                 continue;
-            Loc uloc = ctx->getBelLocation(user.cell->bel);
+            Loc uloc = user.cell->getLocation();
             if (bb.x0 == uloc.x)
                 ++bb.nx0;
             else if (uloc.x < bb.x0) {
@@ -1173,7 +1179,7 @@ class SAPlacer
         nets_by_tile.resize(max_x + 1, std::vector<dict<IdString, int>>(max_y + 1));
         for (auto &cell : ctx->cells) {
             CellInfo *ci = cell.second.get();
-            if (int(ci->ports.size()) > large_cell_thresh)
+            if (ci->isPseudo() || (int(ci->ports.size()) > large_cell_thresh))
                 continue;
             Loc loc = ctx->getBelLocation(ci->bel);
             auto &nbt = nets_by_tile.at(loc.x).at(loc.y);
diff --git a/common/place/placer_heap.cc b/common/place/placer_heap.cc
index 4c9ffb23..bd8cd37d 100644
--- a/common/place/placer_heap.cc
+++ b/common/place/placer_heap.cc
@@ -147,7 +147,7 @@ class HeAPPlacer
         tmg.setup();
 
         for (auto &cell : ctx->cells)
-            if (cell.second->cluster != ClusterId())
+            if (!cell.second->isPseudo() && cell.second->cluster != ClusterId())
                 cluster2cells[cell.second->cluster].push_back(cell.second.get());
     }
 
@@ -284,6 +284,8 @@ class HeAPPlacer
                 // Save solution
                 solution.clear();
                 for (auto &cell : ctx->cells) {
+                    if (cell.second->isPseudo())
+                        continue;
                     solution.emplace_back(cell.second.get(), cell.second->bel, cell.second->belStrength);
                 }
             } else {
@@ -312,6 +314,8 @@ class HeAPPlacer
         }
 
         for (auto &cell : ctx->cells) {
+            if (cell.second->isPseudo())
+                continue;
             if (cell.second->bel == BelId())
                 log_error("Found unbound cell %s\n", cell.first.c_str(ctx));
             if (ctx->getBoundBelCell(cell.second->bel) != cell.second.get())
@@ -411,7 +415,8 @@ class HeAPPlacer
         // Initial constraints placer
         for (auto &cell_entry : ctx->cells) {
             CellInfo *cell = cell_entry.second.get();
-
+            if (cell->isPseudo())
+                continue;
             auto loc = cell->attrs.find(ctx->id("BEL"));
             if (loc != cell->attrs.end()) {
                 std::string loc_name = loc->second.as_string();
@@ -461,6 +466,8 @@ class HeAPPlacer
         pool<IdString> cell_types_in_use;
         pool<BelBucketId> buckets_in_use;
         for (auto &cell : ctx->cells) {
+            if (cell.second->isPseudo())
+                continue;
             IdString cell_type = cell.second->type;
             cell_types_in_use.insert(cell_type);
             BelBucketId bucket = ctx->getBelBucketForCellType(cell_type);
@@ -527,6 +534,8 @@ class HeAPPlacer
     {
         pool<IdString> cell_types;
         for (const auto &cell : ctx->cells) {
+            if (cell.second->isPseudo())
+                continue;
             cell_types.insert(cell.second->type);
         }
 
@@ -551,6 +560,14 @@ class HeAPPlacer
 
         for (auto &cell : ctx->cells) {
             CellInfo *ci = cell.second.get();
+            if (ci->isPseudo()) {
+                Loc loc = ci->pseudo_cell->getLocation();
+                cell_locs[cell.first].x = loc.x;
+                cell_locs[cell.first].y = loc.y;
+                cell_locs[cell.first].locked = true;
+                cell_locs[cell.first].global = false;
+                continue;
+            }
             if (ci->bel != BelId()) {
                 Loc loc = ctx->getBelLocation(ci->bel);
                 cell_locs[cell.first].x = loc.x;
@@ -627,8 +644,9 @@ class HeAPPlacer
         int row = 0;
         solve_cells.clear();
         // First clear the udata of all cells
-        for (auto &cell : ctx->cells)
+        for (auto &cell : ctx->cells) {
             cell.second->udata = dont_solve;
+        }
         // Then update cells to be placed, which excludes cell children
         for (auto cell : place_cells) {
             if (buckets && !buckets->count(ctx->getBelBucketForCellType(cell->type)))