fabulous: Pack, validity check and FASM support for muxes

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

generic/viaduct/fabulous/fabulous.cc

@@ -317,12 +317,13 @@ struct FabulousImpl : ViaductAPI
                 }
                 // K select inputs
                 for (unsigned j = 0; j < k; j++) {
-                    ctx->addBelInput(mux, ctx->idf("S%d", j), data.pins.at(ctx->idf("S%d",
+                    ctx->addBelInput(mux, ctx->idf("S%d", j),
-                        (m == 8 && j == 2) ? 3 : ((i / m) * k + j)
+                                     data.pins.at(ctx->idf("S%d", (m == 8 && j == 2) ? 3 : ((i / m) * k + j))).wire);
-                    )).wire);
                 }
                 // Output
-                IdString output = (m == 2) ? mux_outs.at(i / m) : (m == 4) ? mux_outs.at((i / m) * k + 1) : mux_outs.at(3);
+                IdString output = (m == 2)   ? mux_outs.at(i / m)
+                                  : (m == 4) ? mux_outs.at((i / m) * k + 1)
+                                             : mux_outs.at(3);
                 ctx->addBelOutput(mux, id_O, data.pins.at(output).wire);
             }
         }

generic/viaduct/fabulous/fasm.cc

@@ -123,6 +123,14 @@ struct FabFasmWriter
             write_bool(lc, "NEG_SR");
             write_bool(lc, "ASYNC_SR");
         }
+        if (lc->type.in(id_FABULOUS_MUX4, id_FABULOUS_MUX8)) {
+            // TODO: don't hardcode prefix
+            out << prefix << "I.c0" << std::endl;
+        }
+        if (lc->type == id_FABULOUS_MUX8) {
+            // TODO: don't hardcode prefix
+            out << prefix << "I.c1" << std::endl;
+        }
     }
 
     void write_io(const CellInfo *io)
@@ -161,7 +169,8 @@ struct FabFasmWriter
     void write_cell(const CellInfo *ci)
     {
         out << stringf("# config for cell '%s'\n", ctx->nameOf(ci)) << std::endl;
-        if (ci->type.in(id_FABULOUS_COMB, id_FABULOUS_FF, id_FABULOUS_LC))
+        if (ci->type.in(id_FABULOUS_COMB, id_FABULOUS_FF, id_FABULOUS_LC, id_FABULOUS_MUX2, id_FABULOUS_MUX4,
+                        id_FABULOUS_MUX8))
             write_logic(ci);
         else if (ci->type == id_IO_1_bidirectional_frame_config_pass)
             write_io(ci);

generic/viaduct/fabulous/pack.cc

@@ -132,6 +132,53 @@ struct FabulousPacker
         }
     }
 
+    void pack_muxes()
+    {
+        // TODO: don't hardcode z-offset -- we should come up with our own constraint structure
+        int lut_muxes_dz = 9;
+        int lut_lut_dz = 1;
+        for (auto &cell : ctx->cells) {
+            CellInfo *ci = cell.second.get();
+            unsigned k = 0;
+            if (ci->type == id_FABULOUS_MUX2)
+                k = 1;
+            else if (ci->type == id_FABULOUS_MUX4)
+                k = 2;
+            else if (ci->type == id_FABULOUS_MUX8)
+                k = 3;
+            else
+                continue;
+            unsigned m = (1U << k);
+            std::vector<CellInfo *> luts;
+            for (unsigned i = 0; i < m; i++) {
+                NetInfo *ii = ci->getPort(ctx->idf("I%d", i));
+                if (!ii || !ii->driver.cell || !ii->driver.cell->type.in(id_FABULOUS_LC, id_FABULOUS_COMB) ||
+                    ii->driver.port != id_O)
+                    log_error("mux %s input I%d net %s is not driven by a LUT!\n", ctx->nameOf(ci), i, ctx->nameOf(ii));
+                CellInfo *lut = ii->driver.cell;
+                NPNR_ASSERT(lut->cluster == ClusterId());
+                luts.push_back(lut);
+            }
+            luts.at(0)->cluster = luts.at(0)->name;
+            for (unsigned i = 0; i < m; i++) {
+                luts.at(i)->cluster = luts.at(0)->name;
+                luts.at(i)->constr_x = 0;
+                luts.at(i)->constr_y = 0;
+                luts.at(i)->constr_z = i * lut_lut_dz;
+                luts.at(i)->constr_abs_z = false;
+                if (i > 0)
+                    luts.at(0)->constr_children.push_back(luts.at(i));
+            }
+            int extra_mux_dz = (m == 8) ? 7 : (m == 4) ? 1 : 0;
+            ci->cluster = luts.at(0)->name;
+            ci->constr_x = 0;
+            ci->constr_y = 0;
+            ci->constr_z = lut_muxes_dz + extra_mux_dz;
+            ci->constr_abs_z = false;
+            luts.at(0)->constr_children.push_back(ci);
+        }
+    }
+
     void pack_ffs()
     {
         pool<IdString> to_delete;
@@ -238,6 +285,7 @@ struct FabulousPacker
         handle_constants();
         handle_io();
         pack_luts();
+        pack_muxes();
         prepare_ffs();
         pack_ffs();
     }

generic/viaduct/fabulous/validity_check.cc

@@ -33,6 +33,7 @@ CLBState::CLBState(const LogicConfig &cfg)
     if (cfg.split_lc) {
         ff = std::make_unique<CellInfo *[]>(cfg.lc_per_clb * cfg.ff_per_lc);
     }
+    mux = std::make_unique<CellInfo *[]>(cfg.lc_per_clb);
     // TODO: mux
 }
 
@@ -173,6 +174,26 @@ bool CLBState::check_validity(const LogicConfig &cfg, const CellTagger &cell_dat
             }
         }
     }
+    // don't allow mixed MUX types in the classic fabulous arch where ctrl sigs are shared
+    int tile_mux_type = 0;
+    for (unsigned z = 0; z < cfg.lc_per_clb; z++) {
+        const CellInfo *m = mux[z];
+        if (!m)
+            continue;
+        int this_mux = 0;
+        if (m->type == id_FABULOUS_MUX2)
+            this_mux = 2;
+        else if (m->type == id_FABULOUS_MUX4)
+            this_mux = 4;
+        else if (m->type == id_FABULOUS_MUX8)
+            this_mux = 8;
+        else
+            NPNR_ASSERT_FALSE("unknown mux type");
+        if (tile_mux_type == 0)
+            tile_mux_type = this_mux;
+        else if (tile_mux_type != this_mux)
+            return false;
+    }
     // TODO: other checks...
     return true;
 }