ice40: WIP SB_CARRY packer

Signed-off-by: David Shah <davey1576@gmail.com>

ice40/cells.h

@@ -60,6 +60,16 @@ inline bool is_ff(const Context *ctx, const CellInfo *cell)
            cell->type == ctx->id("SB_DFFNES");
 }
 
+inline bool is_carry(const Context *ctx, const CellInfo *cell)
+{
+    return cell->type == ctx->id("SB_CARRY");
+}
+
+inline bool is_lc(const Context *ctx, const CellInfo *cell)
+{
+    return cell->type == ctx->id("ICESTORM_LC");
+}
+
 // Return true if a cell is a SB_IO
 inline bool is_sb_io(const Context *ctx, const CellInfo *cell)
 {

ice40/pack.cc

@@ -114,6 +114,67 @@ static void pack_nonlut_ffs(Context *ctx)
     }
 }
 
+
+// Pack carry logic
+static void pack_carries(Context *ctx)
+{
+    log_info("Packing carries..\n");
+
+    std::unordered_set<IdString> packed_cells;
+
+    for (auto cell : ctx->cells) {
+        CellInfo *ci = cell.second;
+        if (is_carry(ctx, ci)) {
+            packed_cells.insert(cell.first);
+            CellInfo *carry_ci_lc = net_only_drives(ctx, ci->ports.at("CI").net,
+                                                 is_lc, "I3", false);
+            if (!ci->ports.at("I0").net)
+                log_error("SB_CARRY '%s' has disconnect port I0\n", cell.first.c_str(ctx));
+            if (!ci->ports.at("I1").net)
+                log_error("SB_CARRY '%s' has disconnect port I1\n", cell.first.c_str(ctx));
+
+            std::unordered_set<IdString> i0_matches, i1_matches;
+            auto &i0_usrs = ci->ports.at("I0").net->users;
+            auto &i1_usrs = ci->ports.at("I1").net->users;
+
+            for (auto usr : i0_usrs) {
+                if (is_lc(ctx, usr.cell) && usr.port == ctx->id("I1"))
+                    i0_matches.insert(usr.cell->name);
+            }
+            for (auto usr : i1_usrs) {
+                if (is_lc(ctx, usr.cell) && usr.port == ctx->id("I2"))
+                    i1_matches.insert(usr.cell->name);
+            }
+            std::set<IdString> carry_lcs;
+            std::set_intersection(i0_matches.begin(), i0_matches.end(), i1_matches.begin(), i1_matches.end(), std::inserter(carry_lcs, carry_lcs.begin()));
+            CellInfo *carry_lc = nullptr;
+            if (carry_ci_lc) {
+                if (carry_lcs.find(carry_ci_lc->name) == carry_lcs.end())
+                    log_error("SB_CARRY '%s' cannot be packed into any logic cell (I0 and I1 connections do not match I3 connection)\n", cell.first.c_str(ctx));
+                carry_lc = carry_ci_lc;
+            } else {
+                if (carry_lcs.empty())
+                    log_error("SB_CARRY '%s' cannot be packed into any logic cell (no logic cell connects both I0 and I1)\n", cell.first.c_str(ctx));
+                carry_lc = ctx->cells.at(*carry_lcs.begin());
+            }
+            carry_lc->attrs[ctx->id("CARRY_ENABLE")] = "1";
+            replace_port(ci, "CI", carry_lc, "CIN");
+            replace_port(ci, "CO", carry_lc, "COUT");
+
+            i0_usrs.erase(std::remove_if(i0_usrs.begin(), i0_usrs.end(), [ci, ctx] (const PortRef &pr){
+                return pr.cell == ci && pr.port == ctx->id("I0");
+            }));
+
+            i1_usrs.erase(std::remove_if(i1_usrs.begin(), i1_usrs.end(), [ci, ctx] (const PortRef &pr){
+                return pr.cell == ci && pr.port == ctx->id("I1");
+            }));
+        }
+    }
+    for (auto pcell : packed_cells) {
+        ctx->cells.erase(pcell);
+    }
+}
+
 // "Pack" RAMs
 static void pack_ram(Context *ctx)
 {