generic: Add a simple packer for generic SLICEs and IOBs

Signed-off-by: David Shah <dave@ds0.me>

1 files changed, 293 insertions, 0 deletions

diff --git a/generic/pack.cc b/generic/pack.cc
new file mode 100644
index 00000000..4d4a76a8
--- /dev/null
+++ b/generic/pack.cc
@@ -0,0 +1,293 @@
+/*
+ *  nextpnr -- Next Generation Place and Route
+ *
+ *  Copyright (C) 2018-19  David Shah <david@symbioticeda.com>
+ *
+ *  Permission to use, copy, modify, and/or distribute this software for any
+ *  purpose with or without fee is hereby granted, provided that the above
+ *  copyright notice and this permission notice appear in all copies.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ *  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ *  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ *  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ *  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ *  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ *  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ */
+
+#include <algorithm>
+#include <iterator>
+#include <unordered_set>
+#include "cells.h"
+#include "design_utils.h"
+#include "log.h"
+#include "util.h"
+
+NEXTPNR_NAMESPACE_BEGIN
+
+// Pack LUTs and LUT-FF pairs
+static void pack_lut_lutffs(Context *ctx)
+{
+    log_info("Packing LUT-FFs..\n");
+
+    std::unordered_set<IdString> packed_cells;
+    std::vector<std::unique_ptr<CellInfo>> new_cells;
+    for (auto cell : sorted(ctx->cells)) {
+        CellInfo *ci = cell.second;
+        if (ctx->verbose)
+            log_info("cell '%s' is of type '%s'\n", ci->name.c_str(ctx), ci->type.c_str(ctx));
+        if (is_lut(ctx, ci)) {
+            std::unique_ptr<CellInfo> packed =
+                    create_generic_cell(ctx, ctx->id("GENERIC_SLICE"), ci->name.str(ctx) + "_LC");
+            std::copy(ci->attrs.begin(), ci->attrs.end(), std::inserter(packed->attrs, packed->attrs.begin()));
+            packed_cells.insert(ci->name);
+            if (ctx->verbose)
+                log_info("packed cell %s into %s\n", ci->name.c_str(ctx), packed->name.c_str(ctx));
+            // See if we can pack into a DFF
+            // TODO: LUT cascade
+            NetInfo *o = ci->ports.at(ctx->id("Q")).net;
+            CellInfo *dff = net_only_drives(ctx, o, is_ff, ctx->id("D"), true);
+            auto lut_bel = ci->attrs.find(ctx->id("BEL"));
+            bool packed_dff = false;
+            if (dff) {
+                if (ctx->verbose)
+                    log_info("found attached dff %s\n", dff->name.c_str(ctx));
+                auto dff_bel = dff->attrs.find(ctx->id("BEL"));
+                if (lut_bel != ci->attrs.end() && dff_bel != dff->attrs.end() && lut_bel->second != dff_bel->second) {
+                    // Locations don't match, can't pack
+                } else {
+                    lut_to_lc(ctx, ci, packed.get(), false);
+                    dff_to_lc(ctx, dff, packed.get(), false);
+                    ctx->nets.erase(o->name);
+                    if (dff_bel != dff->attrs.end())
+                        packed->attrs[ctx->id("BEL")] = dff_bel->second;
+                    packed_cells.insert(dff->name);
+                    if (ctx->verbose)
+                        log_info("packed cell %s into %s\n", dff->name.c_str(ctx), packed->name.c_str(ctx));
+                    packed_dff = true;
+                }
+            }
+            if (!packed_dff) {
+                lut_to_lc(ctx, ci, packed.get(), true);
+            }
+            new_cells.push_back(std::move(packed));
+        }
+    }
+    for (auto pcell : packed_cells) {
+        ctx->cells.erase(pcell);
+    }
+    for (auto &ncell : new_cells) {
+        ctx->cells[ncell->name] = std::move(ncell);
+    }
+}
+
+// Pack FFs not packed as LUTFFs
+static void pack_nonlut_ffs(Context *ctx)
+{
+    log_info("Packing non-LUT FFs..\n");
+
+    std::unordered_set<IdString> packed_cells;
+    std::vector<std::unique_ptr<CellInfo>> new_cells;
+
+    for (auto cell : sorted(ctx->cells)) {
+        CellInfo *ci = cell.second;
+        if (is_ff(ctx, ci)) {
+            std::unique_ptr<CellInfo> packed =
+                    create_generic_cell(ctx, ctx->id("GENERIC_SLICE"), ci->name.str(ctx) + "_DFFLC");
+            std::copy(ci->attrs.begin(), ci->attrs.end(), std::inserter(packed->attrs, packed->attrs.begin()));
+            if (ctx->verbose)
+                log_info("packed cell %s into %s\n", ci->name.c_str(ctx), packed->name.c_str(ctx));
+            packed_cells.insert(ci->name);
+            dff_to_lc(ctx, ci, packed.get(), true);
+            new_cells.push_back(std::move(packed));
+        }
+    }
+    for (auto pcell : packed_cells) {
+        ctx->cells.erase(pcell);
+    }
+    for (auto &ncell : new_cells) {
+        ctx->cells[ncell->name] = std::move(ncell);
+    }
+}
+
+static bool net_is_constant(const Context *ctx, NetInfo *net, bool &value)
+{
+    if (net == nullptr)
+        return false;
+    if (net->name == ctx->id("$PACKER_GND_NET") || net->name == ctx->id("$PACKER_VCC_NET")) {
+        value = (net->name == ctx->id("$PACKER_VCC_NET"));
+        return true;
+    } else {
+        return false;
+    }
+}
+
+// Merge a net into a constant net
+static void set_net_constant(const Context *ctx, NetInfo *orig, NetInfo *constnet, bool constval)
+{
+    orig->driver.cell = nullptr;
+    for (auto user : orig->users) {
+        if (user.cell != nullptr) {
+            CellInfo *uc = user.cell;
+            if (ctx->verbose)
+                log_info("%s user %s\n", orig->name.c_str(ctx), uc->name.c_str(ctx));
+            if ((is_lut(ctx, uc) || is_lc(ctx, uc)) && (user.port.str(ctx).at(0) == 'I') && !constval) {
+                uc->ports[user.port].net = nullptr;
+            } else {
+                uc->ports[user.port].net = constnet;
+                constnet->users.push_back(user);
+            }
+        }
+    }
+    orig->users.clear();
+}
+
+// Pack constants (simple implementation)
+static void pack_constants(Context *ctx)
+{
+    log_info("Packing constants..\n");
+
+    std::unique_ptr<CellInfo> gnd_cell = create_generic_cell(ctx, ctx->id("GENERIC_SLICE"), "$PACKER_GND");
+    gnd_cell->params[ctx->id("INIT")] = "0";
+    std::unique_ptr<NetInfo> gnd_net = std::unique_ptr<NetInfo>(new NetInfo);
+    gnd_net->name = ctx->id("$PACKER_GND_NET");
+    gnd_net->driver.cell = gnd_cell.get();
+    gnd_net->driver.port = ctx->id("Q");
+    gnd_cell->ports.at(ctx->id("Q")).net = gnd_net.get();
+
+    std::unique_ptr<CellInfo> vcc_cell = create_generic_cell(ctx, ctx->id("GENERIC_SLICE"), "$PACKER_VCC");
+    vcc_cell->params[ctx->id("INIT")] = "1";
+    std::unique_ptr<NetInfo> vcc_net = std::unique_ptr<NetInfo>(new NetInfo);
+    vcc_net->name = ctx->id("$PACKER_VCC_NET");
+    vcc_net->driver.cell = vcc_cell.get();
+    vcc_net->driver.port = ctx->id("Q");
+    vcc_cell->ports.at(ctx->id("Q")).net = vcc_net.get();
+
+    std::vector<IdString> dead_nets;
+
+    bool gnd_used = false;
+
+    for (auto net : sorted(ctx->nets)) {
+        NetInfo *ni = net.second;
+        if (ni->driver.cell != nullptr && ni->driver.cell->type == ctx->id("GND")) {
+            IdString drv_cell = ni->driver.cell->name;
+            set_net_constant(ctx, ni, gnd_net.get(), false);
+            gnd_used = true;
+            dead_nets.push_back(net.first);
+            ctx->cells.erase(drv_cell);
+        } else if (ni->driver.cell != nullptr && ni->driver.cell->type == ctx->id("VCC")) {
+            IdString drv_cell = ni->driver.cell->name;
+            set_net_constant(ctx, ni, vcc_net.get(), true);
+            dead_nets.push_back(net.first);
+            ctx->cells.erase(drv_cell);
+        }
+    }
+
+    if (gnd_used) {
+        ctx->cells[gnd_cell->name] = std::move(gnd_cell);
+        ctx->nets[gnd_net->name] = std::move(gnd_net);
+    }
+    // Vcc cell always inserted for now, as it may be needed during carry legalisation (TODO: trim later if actually
+    // never used?)
+    ctx->cells[vcc_cell->name] = std::move(vcc_cell);
+    ctx->nets[vcc_net->name] = std::move(vcc_net);
+
+    for (auto dn : dead_nets) {
+        ctx->nets.erase(dn);
+    }
+}
+
+static bool is_nextpnr_iob(Context *ctx, CellInfo *cell)
+{
+    return cell->type == ctx->id("$nextpnr_ibuf") || cell->type == ctx->id("$nextpnr_obuf") ||
+           cell->type == ctx->id("$nextpnr_iobuf");
+}
+
+static bool is_generic_iob(const Context *ctx, const CellInfo *cell) { return cell->type == ctx->id("GENERIC_IOB"); }
+
+// Pack IO buffers
+static void pack_io(Context *ctx)
+{
+    std::unordered_set<IdString> packed_cells;
+    std::unordered_set<IdString> delete_nets;
+
+    std::vector<std::unique_ptr<CellInfo>> new_cells;
+    log_info("Packing IOs..\n");
+
+    for (auto cell : sorted(ctx->cells)) {
+        CellInfo *ci = cell.second;
+        if (is_nextpnr_iob(ctx, ci)) {
+            CellInfo *iob = nullptr;
+            if (ci->type == ctx->id("$nextpnr_ibuf") || ci->type == ctx->id("$nextpnr_iobuf")) {
+                iob = net_only_drives(ctx, ci->ports.at(ctx->id("O")).net, is_generic_iob, ctx->id("PAD"), true, ci);
+
+            } else if (ci->type == ctx->id("$nextpnr_obuf")) {
+                NetInfo *net = ci->ports.at(ctx->id("I")).net;
+                iob = net_only_drives(ctx, net, is_generic_iob, ctx->id("PAD"), true, ci);
+            }
+            if (iob != nullptr) {
+                // Trivial case, GENERIC_IOB used. Just destroy the net and the
+                // iobuf
+                log_info("%s feeds GENERIC_IOB %s, removing %s %s.\n", ci->name.c_str(ctx), iob->name.c_str(ctx),
+                         ci->type.c_str(ctx), ci->name.c_str(ctx));
+                NetInfo *net = iob->ports.at(ctx->id("PAD")).net;
+                if (((ci->type == ctx->id("$nextpnr_ibuf") || ci->type == ctx->id("$nextpnr_iobuf")) &&
+                     net->users.size() > 1) ||
+                    (ci->type == ctx->id("$nextpnr_obuf") && (net->users.size() > 2 || net->driver.cell != nullptr)))
+                    log_error("PAD of %s '%s' connected to more than a single top level IO.\n", iob->type.c_str(ctx),
+                              iob->name.c_str(ctx));
+
+                if (net != nullptr) {
+                    delete_nets.insert(net->name);
+                    iob->ports.at(ctx->id("PAD")).net = nullptr;
+                }
+                if (ci->type == ctx->id("$nextpnr_iobuf")) {
+                    NetInfo *net2 = ci->ports.at(ctx->id("I")).net;
+                    if (net2 != nullptr) {
+                        delete_nets.insert(net2->name);
+                    }
+                }
+            } else {
+                // Create a GENERIC_IOB buffer
+                std::unique_ptr<CellInfo> ice_cell =
+                        create_generic_cell(ctx, ctx->id("GENERIC_IOB"), ci->name.str(ctx) + "$sb_io");
+                nxio_to_iob(ctx, ci, ice_cell.get(), packed_cells);
+                new_cells.push_back(std::move(ice_cell));
+                iob = new_cells.back().get();
+            }
+            packed_cells.insert(ci->name);
+            std::copy(ci->attrs.begin(), ci->attrs.end(), std::inserter(iob->attrs, iob->attrs.begin()));
+        }
+    }
+    for (auto pcell : packed_cells) {
+        ctx->cells.erase(pcell);
+    }
+    for (auto dnet : delete_nets) {
+        ctx->nets.erase(dnet);
+    }
+    for (auto &ncell : new_cells) {
+        ctx->cells[ncell->name] = std::move(ncell);
+    }
+}
+
+// Main pack function
+bool Arch::pack()
+{
+    Context *ctx = getCtx();
+    try {
+        log_break();
+        pack_constants(ctx);
+        pack_io(ctx);
+        pack_lut_lutffs(ctx);
+        pack_nonlut_ffs(ctx);
+        ctx->assignArchInfo();
+        log_info("Checksum: 0x%08x\n", ctx->checksum());
+        return true;
+    } catch (log_execution_error_exception) {
+        return false;
+    }
+}
+
+NEXTPNR_NAMESPACE_END