Implement getBelValidityConflict for gatemate

Signed-off-by: gatecat <gatecat@ds0.me>

common/place/placer_heap.cc

@@ -1003,7 +1003,26 @@ class HeAPPlacer
                             }
                             // Provisionally bind the bel
                             ctx->bindBel(sz, ci, STRENGTH_WEAK);
+                            // Handle legality-driven ripups
+                            bool is_illegal = false;
+                            CellInfo *conflict = nullptr;
+                            BelId conflict_bel = BelId();
+
                             if (require_validity && !ctx->isBelLocationValid(sz)) {
+                                conflict = ctx->getBelValidityConflict(sz);
+                                // Only rip up conflicts without constraints
+                                if (!conflict || conflict->cluster != ClusterId() || conflict->belStrength > STRENGTH_WEAK) {
+                                    is_illegal = true;
+                                    conflict = nullptr; // so we don't add it back to remaining later
+                                } else {
+                                    conflict_bel = conflict->bel;
+                                    ctx->unbindBel(conflict_bel);
+                                    // This is the contract for getBelValidityConflict that the ripup has to make the location valid
+                                    NPNR_ASSERT(ctx->isBelLocationValid(sz));
+                                }
+                            }
+
+                            if (is_illegal) {
                                 // New location is not legal; unbind the cell (and rebind the cell we ripped up if
                                 // applicable)
                                 ctx->unbindBel(sz);
@@ -1012,6 +1031,8 @@ class HeAPPlacer
                             } else if (iter_at_radius < need_to_explore) {
                                 // It's legal, but we haven't tried enough locations yet
                                 ctx->unbindBel(sz);
+                                if (conflict != nullptr)
+                                    ctx->bindBel(conflict_bel, conflict, STRENGTH_WEAK);
                                 if (bound != nullptr)
                                     ctx->bindBel(sz, bound, STRENGTH_WEAK);
                                 int input_len = 0;
@@ -1040,6 +1061,10 @@ class HeAPPlacer
                                     remaining.emplace(chain_size[bound->name] *
                                                               cfg.get_cell_legalisation_weight(ctx, bound),
                                                       bound->name);
+                                if (conflict != nullptr)
+                                    remaining.emplace(chain_size[conflict->name] *
+                                                              cfg.get_cell_legalisation_weight(ctx, conflict),
+                                                      conflict->name);
                                 Loc loc = ctx->getBelLocation(sz);
                                 cell_locs[ci->name].x = loc.x;
                                 cell_locs[ci->name].y = loc.y;

himbaechel/arch.h

@@ -688,6 +688,10 @@ struct Arch : BaseArch<ArchRanges>
     {
         return uarch->isBelLocationValid(bel, explain_invalid);
     }
+    CellInfo *getBelValidityConflict(BelId bel) const override
+    {
+        return uarch->getBelValidityConflict(bel);
+    }
 
     // ------------------------------------------------
 

himbaechel/himbaechel_api.h

@@ -79,6 +79,7 @@ struct HimbaechelAPI
     virtual BelBucketId getBelBucketForCellType(IdString cell_type) const;
     virtual bool isValidBelForCellType(IdString cell_type, BelId bel) const;
     virtual bool isBelLocationValid(BelId bel, bool explain_invalid = false) const { return true; }
+    virtual CellInfo *getBelValidityConflict(BelId bel) const { return nullptr; }
 
     // --- Wire and pip functions ---
     // Called when a wire/pip is placed/unplaced (with net=nullptr for a unbind)

himbaechel/uarch/gatemate/gatemate.cc

@@ -210,6 +210,28 @@ bool GateMateImpl::isBelLocationValid(BelId bel, bool explain_invalid) const
     return true;
 }
 
+CellInfo *GateMateImpl::getBelValidityConflict(BelId bel) const
+{
+    if (ctx->getBelBucketForBel(bel) == id_RAM_HALF) {
+        CellInfo *cell = ctx->getBoundBelCell(bel);
+        Loc loc = ctx->getBelLocation(bel);
+        CellInfo *adj_half =
+                ctx->getBoundBelCell(ctx->getBelByLocation(Loc(loc.x, loc.z == RAM_HALF_L_Z ? loc.y - 8 : loc.y + 8,
+                                                               loc.z == RAM_HALF_L_Z ? RAM_HALF_U_Z : RAM_HALF_L_Z)));
+        if (adj_half) {
+            const auto &half_data = fast_cell_info.at(cell->flat_index);
+            if (half_data.used) {
+                const auto &adj_data = fast_cell_info.at(adj_half->flat_index);
+                if (adj_data.used) {
+                    if (adj_data.config != half_data.config)
+                        return adj_half;
+                }
+            }
+        }
+    }
+    return nullptr;
+}
+
 Loc GateMateImpl::getRelativeConstraint(Loc &root_loc, IdString id) const
 {
     Loc child_loc;

himbaechel/uarch/gatemate/gatemate.h

@@ -50,6 +50,8 @@ struct GateMateImpl : HimbaechelAPI
     bool checkPipAvailForNet(PipId pip, const NetInfo *net) const override { return checkPipAvail(pip); };
 
     bool isBelLocationValid(BelId bel, bool explain_invalid = false) const override;
+    CellInfo *getBelValidityConflict(BelId bel) const override;
+
     delay_t estimateDelay(WireId src, WireId dst) const override;
     bool getCellDelay(const CellInfo *cell, IdString fromPort, IdString toPort, DelayQuad &delay) const override;
     TimingPortClass getPortTimingClass(const CellInfo *cell, IdString port, int &clockInfoCount) const override;