merge

4 files changed, 195 insertions, 51 deletions

diff --git a/common/nextpnr.h b/common/nextpnr.h
index df9d7e3e..71a52758 100644
--- a/common/nextpnr.h
+++ b/common/nextpnr.h
@@ -207,13 +207,13 @@ struct BaseCtx
         IdString::initialize_add(this, "", 0);
         IdString::initialize_arch(this);
     }
-    
+
     ~BaseCtx()
     {
-        for(auto &item : nets) {
+        for (auto &item : nets) {
             delete item.second;
         }
-        for(auto &item : cells) {
+        for (auto &item : cells) {
             delete item.second;
         }
         delete idstring_str_to_idx;
diff --git a/ice40/cells.cc b/ice40/cells.cc
index ddb69f4f..e9c75649 100644
--- a/ice40/cells.cc
+++ b/ice40/cells.cc
@@ -47,6 +47,8 @@ CellInfo *create_ice_cell(Context *ctx, IdString type, std::string name)
         new_cell->params[ctx->id("DFF_ENABLE")] = "0";
         new_cell->params[ctx->id("SET_NORESET")] = "0";
         new_cell->params[ctx->id("ASYNC_SR")] = "0";
+        new_cell->params[ctx->id("CIN_CONST")] = "0";
+        new_cell->params[ctx->id("CIN_SET")] = "0";
 
         add_port(ctx, new_cell, "I0", PORT_IN);
         add_port(ctx, new_cell, "I1", PORT_IN);
diff --git a/ice40/pack.cc b/ice40/pack.cc
index 2378a625..dd9fba27 100644
--- a/ice40/pack.cc
+++ b/ice40/pack.cc
@@ -258,7 +258,7 @@ static void pack_constants(Context *ctx)
 
     std::vector<IdString> dead_nets;
 
-    bool gnd_used = false, vcc_used = false;
+    bool gnd_used = false;
 
     for (auto net : sorted(ctx->nets)) {
         NetInfo *ni = net.second;
@@ -268,7 +268,6 @@ static void pack_constants(Context *ctx)
             dead_nets.push_back(net.first);
         } else if (ni->driver.cell != nullptr && ni->driver.cell->type == ctx->id("VCC")) {
             set_net_constant(ctx, ni, vcc_net, true);
-            vcc_used = true;
             dead_nets.push_back(net.first);
         }
     }
@@ -280,14 +279,10 @@ static void pack_constants(Context *ctx)
         delete gnd_net;
         delete gnd_cell;
     }
-
-    if (vcc_used) {
-        ctx->cells[vcc_cell->name] = vcc_cell;
-        ctx->nets[vcc_net->name] = vcc_net;
-    } else {
-        delete vcc_net;
-        delete vcc_cell;
-    }
+    // Vcc cell always inserted for now, as it may be needed during carry legalisation (TODO: trim later if actually
+    // never used?)
+    ctx->cells[vcc_cell->name] = vcc_cell;
+    ctx->nets[vcc_net->name] = vcc_net;
 
     for (auto dn : dead_nets)
         ctx->nets.erase(dn);
diff --git a/ice40/place_legaliser.cc b/ice40/place_legaliser.cc
index 83316d6e..52a116b2 100644
--- a/ice40/place_legaliser.cc
+++ b/ice40/place_legaliser.cc
@@ -27,13 +27,18 @@
 
 NEXTPNR_NAMESPACE_BEGIN
 
+struct CellChain
+{
+    std::vector<CellInfo *> cells;
+};
+
 // Generic chain finder
 template <typename F1, typename F2, typename F3>
-std::vector<std::vector<CellInfo *>> find_chains(const Context *ctx, F1 cell_type_predicate, F2 get_previous,
-                                                 F3 get_next, size_t min_length = 2)
+std::vector<CellChain> find_chains(const Context *ctx, F1 cell_type_predicate, F2 get_previous, F3 get_next,
+                                   size_t min_length = 2)
 {
     std::set<IdString> chained;
-    std::vector<std::vector<CellInfo *>> chains;
+    std::vector<CellChain> chains;
     for (auto cell : sorted(ctx->cells)) {
         if (chained.find(cell.first) != chained.end())
             continue;
@@ -45,15 +50,15 @@ std::vector<std::vector<CellInfo *>> find_chains(const Context *ctx, F1 cell_typ
                 start = prev_start;
                 prev_start = get_previous(ctx, start);
             }
-            std::vector<CellInfo *> chain;
+            CellChain chain;
             CellInfo *end = start;
             while (end != nullptr) {
-                chain.push_back(end);
+                chain.cells.push_back(end);
                 end = get_next(ctx, end);
             }
-            if (chain.size() >= min_length) {
+            if (chain.cells.size() >= min_length) {
                 chains.push_back(chain);
-                for (auto c : chain)
+                for (auto c : chain.cells)
                     chained.insert(c->name);
             }
         }
@@ -61,10 +66,11 @@ std::vector<std::vector<CellInfo *>> find_chains(const Context *ctx, F1 cell_typ
     return chains;
 }
 
-static void get_chain_midpoint(const Context *ctx, const std::vector<CellInfo *> &chain, float &x, float &y) {
+static void get_chain_midpoint(const Context *ctx, const CellChain &chain, float &x, float &y)
+{
     float total_x = 0, total_y = 0;
     int N = 0;
-    for (auto cell : chain) {
+    for (auto cell : chain.cells) {
         if (cell->bel == BelId())
             continue;
         int bel_x, bel_y;
@@ -79,38 +85,179 @@ static void get_chain_midpoint(const Context *ctx, const std::vector<CellInfo *>
     y = total_y / N;
 }
 
-static CellInfo *make_carry_pass_out(Context *ctx, PortInfo &cout_port) {
-    assert(cout_port.net != nullptr);
-    CellInfo *lc = create_ice_cell(ctx, ctx->id("ICESTORM_LC"));
-    lc->params[ctx->id("LUT_INIT")] = "65280"; // 0xff00: O = I3
-    lc->ports.at(ctx->id("O")).net = cout_port.net;
-    NetInfo *co_i3_net = new NetInfo();
-    co_i3_net->name = ctx->id(lc->name.str(ctx) + "$I3");
-    co_i3_net->driver = cout_port.net->driver;
-    PortRef i3_r;
-    i3_r.port = ctx->id("I3");
-    i3_r.cell = lc;
-    co_i3_net->users.push_back(i3_r);
-    PortRef o_r;
-    o_r.port = ctx->id("O");
-    o_r.cell = lc;
-    cout_port.net->driver = o_r;
-    lc->ports.at(ctx->id("I3")).net = co_i3_net;
-    return lc;
-}
+class PlacementLegaliser
+{
+  public:
+    PlacementLegaliser(Context *ctx) : ctx(ctx){};
+
+    bool legalise()
+    {
+        bool legalised_carries = legalise_carries();
+        if (!legalised_carries && !ctx->force)
+            return false;
+        return legalised_carries;
+    }
+
+  private:
+    void init_logic_cells()
+    {
+        for (auto bel : ctx->getBels()) {
+            // Initialise the logic bels vector with unavailable invalid bels, dimensions [0..width][0..height[0..7]
+            logic_bels.resize(ctx->chip_info->width + 1,
+                              std::vector<std::vector<std::pair<BelId, bool>>>(
+                                      ctx->chip_info->height + 1,
+                                      std::vector<std::pair<BelId, bool>>(8, std::make_pair(BelId(), true))));
+            if (ctx->getBelType(bel) == TYPE_ICESTORM_LC) {
+                // Using the non-standard API here to get (x, y, z) rather than just (x, y)
+                auto bi = ctx->chip_info->bel_data[bel.index];
+                int x = bi.x, y = bi.y, z = bi.z;
+                IdString cell = ctx->getBoundBelCell(bel);
+                if (cell != IdString() && ctx->cells.at(cell)->belStrength >= STRENGTH_FIXED)
+                    logic_bels.at(x).at(y).at(z) = std::make_pair(bel, true);
+                else
+                    logic_bels.at(x).at(y).at(z) = std::make_pair(bel, false);
+            }
+        }
+    }
+
+    bool legalise_carries()
+    {
+        std::vector<CellChain> carry_chains = find_chains(
+                ctx, is_lc,
+                [](const Context *ctx, const CellInfo *cell) {
+                    return net_driven_by(ctx, cell->ports.at(ctx->id("CIN")).net, is_lc, ctx->id("COUT"));
+                },
+                [](const Context *ctx, const CellInfo *cell) {
+                    return net_only_drives(ctx, cell->ports.at(ctx->id("COUT")).net, is_lc, ctx->id("CIN"), false);
+                });
+        int width = ctx->chip_info->width, height = ctx->chip_info->height;
+        for (auto &base_chain : carry_chains) {
+            std::vector<CellChain> split_chains = split_carry_chain(base_chain);
+            for (auto &chain : split_chains) {
+                float mid_x, mid_y;
+                get_chain_midpoint(ctx, chain, mid_x, mid_y);
+                float base_x = mid_x, base_y = mid_y - (chain.cells.size() / 16.0f);
+                // Find Bel meeting requirements closest to the target base
+            }
+        }
+        return true;
+    }
+
+    // Find Bel closest to a location, meeting chain requirements
+    BelId find_closest_bel(float x, float y, int chain_size)
+    {
+        // TODO
+        return BelId();
+    }
+
+    // Split a carry chain into multiple legal chains
+    std::vector<CellChain> split_carry_chain(CellChain &carryc)
+    {
+        bool start_of_chain = true;
+        std::vector<CellChain> chains;
+        std::vector<const CellInfo *> tile;
+        const int max_length = (ctx->chip_info->height - 2) * 8 - 2;
+        auto curr_cell = carryc.cells.begin();
+        while (curr_cell != carryc.cells.end()) {
+            CellInfo *cell = *curr_cell;
+            if (tile.size() >= 8) {
+                tile.clear();
+            }
+            if (start_of_chain) {
+                tile.clear();
+                chains.emplace_back();
+                start_of_chain = false;
+                if (cell->ports.at(ctx->id("CIN")).net) {
+                    // CIN is not constant and not part of a chain. Must feed in from fabric
+                    CellInfo *feedin = make_carry_feed_in(cell, cell->ports.at(ctx->id("CIN")));
+                    chains.back().cells.push_back(feedin);
+                    tile.push_back(feedin);
+                }
+            }
+            tile.push_back(cell);
+            chains.back().cells.push_back(cell);
+            bool split_chain = (!ctx->logicCellsCompatible(tile)) || (int(chains.back().cells.size()) > max_length);
+            if (split_chain) {
+                CellInfo *passout = make_carry_pass_out(cell->ports.at(ctx->id("COUT")));
+                tile.pop_back();
+                chains.back().cells.back() = passout;
+                start_of_chain = true;
+            } else {
+                NetInfo *carry_net = cell->ports.at(ctx->id("COUT")).net;
+                if (carry_net != nullptr && carry_net->users.size() > 1) {
+                    CellInfo *passout = make_carry_pass_out(cell->ports.at(ctx->id("COUT")));
+                    chains.back().cells.push_back(passout);
+                    tile.push_back(passout);
+                }
+                ++curr_cell;
+            }
+        }
+        return chains;
+    }
+
+    // Insert a logic cell to legalise a COUT->fabric connection
+    CellInfo *make_carry_pass_out(PortInfo &cout_port)
+    {
+        assert(cout_port.net != nullptr);
+        CellInfo *lc = create_ice_cell(ctx, ctx->id("ICESTORM_LC"));
+        lc->params[ctx->id("LUT_INIT")] = "65280"; // 0xff00: O = I3
+        lc->params[ctx->id("CARRY_ENABLE")] = "1";
+        lc->ports.at(ctx->id("O")).net = cout_port.net;
+        NetInfo *co_i3_net = new NetInfo();
+        co_i3_net->name = ctx->id(lc->name.str(ctx) + "$I3");
+        co_i3_net->driver = cout_port.net->driver;
+        PortRef i3_r;
+        i3_r.port = ctx->id("I3");
+        i3_r.cell = lc;
+        co_i3_net->users.push_back(i3_r);
+        PortRef o_r;
+        o_r.port = ctx->id("O");
+        o_r.cell = lc;
+        cout_port.net->driver = o_r;
+        lc->ports.at(ctx->id("I3")).net = co_i3_net;
+        // I1=1 feeds carry up the chain, so no need to actually break the chain
+        lc->ports.at(ctx->id("I1")).net = ctx->nets.at(ctx->id("$PACKER_VCC_NET"));
+        PortRef i1_r;
+        i1_r.port = ctx->id("I1");
+        i1_r.cell = lc;
+        ctx->nets.at(ctx->id("$PACKER_VCC_NET"))->users.push_back(i1_r);
+        ctx->cells[lc->name] = lc;
+        createdCells.insert(lc->name);
+        return lc;
+    }
+
+    // Insert a logic cell to legalise a CIN->fabric connection
+    CellInfo *make_carry_feed_in(CellInfo *cin_cell, PortInfo &cin_port)
+    {
+        assert(cin_port.net != nullptr);
+        CellInfo *lc = create_ice_cell(ctx, ctx->id("ICESTORM_LC"));
+        lc->params[ctx->id("CARRY_ENABLE")] = "1";
+        lc->params[ctx->id("CIN_CONST")] = "1";
+        lc->params[ctx->id("CIN_SET")] = "1";
+        lc->ports.at(ctx->id("I1")).net = cin_port.net;
+        cin_port.net->users.erase(std::remove_if(cin_port.net->users.begin(), cin_port.net->users.end(),
+                                                 [cin_cell, cin_port](const PortRef &usr) {
+                                                     return usr.cell == cin_cell && usr.port == cin_port.name;
+                                                 }));
+        NetInfo *out_net = new NetInfo();
+        out_net->name = ctx->id(lc->name.str(ctx) + "$O");
+
+        ctx->cells[lc->name] = lc;
+        createdCells.insert(lc->name);
+        return lc;
+    }
+
+    Context *ctx;
+    std::unordered_set<IdString> rippedCells;
+    std::unordered_set<IdString> createdCells;
+    // Go from X and Y position to logic cells, setting occupied to true if a Bel is unavailable
+    std::vector<std::vector<std::vector<std::pair<BelId, bool>>>> logic_bels;
+};
 
 bool legalise_design(Context *ctx)
 {
-    std::vector<std::vector<CellInfo *>> carry_chains = find_chains(
-            ctx, is_lc,
-            [](const Context *ctx, const CellInfo *cell) {
-                return net_driven_by(ctx, cell->ports.at(ctx->id("CIN")).net, is_lc, ctx->id("COUT"));
-            },
-            [](const Context *ctx, const CellInfo *cell) {
-                return net_only_drives(ctx, cell->ports.at(ctx->id("COUT")).net, is_lc, ctx->id("CIN"), false);
-            });
-    // TODO
-    return true;
+    PlacementLegaliser lg(ctx);
+    return lg.legalise();
 }
 
 NEXTPNR_NAMESPACE_END