diff options
Diffstat (limited to 'nexus/post_place.cc')
| -rw-r--r-- | nexus/post_place.cc | 161 |
1 files changed, 161 insertions, 0 deletions
diff --git a/nexus/post_place.cc b/nexus/post_place.cc new file mode 100644 index 00000000..65676188 --- /dev/null +++ b/nexus/post_place.cc @@ -0,0 +1,161 @@ +/* + * nextpnr -- Next Generation Place and Route + * + * Copyright (C) 2020 David Shah <dave@ds0.me> + * + * 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 "design_utils.h" +#include "log.h" +#include "nextpnr.h" +#include "timing.h" +#include "util.h" + +NEXTPNR_NAMESPACE_BEGIN + +struct NexusPostPlaceOpt +{ + Context *ctx; + NetCriticalityMap net_crit; + + NexusPostPlaceOpt(Context *ctx) : ctx(ctx){}; + + inline bool is_constrained(CellInfo *cell) + { + return cell->constr_parent != nullptr || !cell->constr_children.empty(); + } + + bool swap_cell_placement(CellInfo *cell, BelId new_bel) + { + if (is_constrained(cell)) + return false; + BelId oldBel = cell->bel; + CellInfo *other_cell = ctx->getBoundBelCell(new_bel); + if (other_cell != nullptr && (is_constrained(other_cell) || other_cell->belStrength > STRENGTH_WEAK)) { + return false; + } + + ctx->unbindBel(oldBel); + if (other_cell != nullptr) { + ctx->unbindBel(new_bel); + } + + ctx->bindBel(new_bel, cell, STRENGTH_WEAK); + + if (other_cell != nullptr) { + ctx->bindBel(oldBel, other_cell, STRENGTH_WEAK); + } + + if (!ctx->isBelLocationValid(new_bel) || ((other_cell != nullptr && !ctx->isBelLocationValid(oldBel)))) { + // New placement is not legal. + ctx->unbindBel(new_bel); + if (other_cell != nullptr) + ctx->unbindBel(oldBel); + + // Revert. + ctx->bindBel(oldBel, cell, STRENGTH_WEAK); + if (other_cell != nullptr) + ctx->bindBel(new_bel, other_cell, STRENGTH_WEAK); + return false; + } + + return true; + } + + int get_distance(BelId a, BelId b) + { + Loc la = ctx->getBelLocation(a); + Loc lb = ctx->getBelLocation(b); + return std::abs(la.x - lb.x) + std::abs(la.y - lb.y); + } + + BelId lut_to_ff(BelId lut) + { + Loc ff_loc = ctx->getBelLocation(lut); + ff_loc.z += (Arch::BEL_FF0 - Arch::BEL_LUT0); + return ctx->getBelByLocation(ff_loc); + } + + void opt_lutffs() + { + int moves_made = 0; + for (auto cell : sorted(ctx->cells)) { + // Search for FF cells + CellInfo *ff = cell.second; + if (ff->type != id_OXIDE_FF) + continue; + // Check M ('fabric') input net + NetInfo *m = get_net_or_empty(ff, id_M); + if (m == nullptr) + continue; + + // Ignore FFs that need both DI and M (PRLD mode) + if (get_net_or_empty(ff, id_DI) != nullptr) + continue; + + const auto &drv = m->driver; + // Skip if driver isn't a LUT/MUX2 + if (drv.cell == nullptr || drv.cell->type != id_OXIDE_COMB || (drv.port != id_F && drv.port != id_OFX)) + continue; + CellInfo *lut = drv.cell; + // Check distance to move isn't too far + if (get_distance(ff->bel, lut->bel) > lut_ff_radius) + continue; + // Find the bel we plan to move into + BelId dest_ff = lut_to_ff(lut->bel); + NPNR_ASSERT(dest_ff != BelId()); + NPNR_ASSERT(ctx->getBelType(dest_ff) == id_OXIDE_FF); + // Ended up in the ideal location by chance + if (dest_ff != ff->bel) { + // If dest_ff is already placed *and* using direct 'DI' input, don't touch it + CellInfo *dest_ff_cell = ctx->getBoundBelCell(dest_ff); + if (dest_ff_cell != nullptr && get_net_or_empty(dest_ff_cell, id_DI) != nullptr) + continue; + // Attempt the swap + bool swap_result = swap_cell_placement(ff, dest_ff); + if (!swap_result) + continue; + } + // Use direct interconnect + rename_port(ctx, ff, id_M, id_DI); + ff->params[id_SEL] = std::string("DL"); + ++moves_made; + continue; + } + log_info(" created %d direct LUT-FF pairs\n", moves_made); + } + + void operator()() + { + get_criticalities(ctx, &net_crit); + opt_lutffs(); + } + + // Configuration + const int lut_ff_radius = 2; + const int lut_lut_radius = 1; + const float lut_lut_crit = 0.85; +}; + +void Arch::post_place_opt() +{ + if (bool_or_default(settings, id("no_post_place_opt"))) + return; + log_info("Running post-place optimisations...\n"); + NexusPostPlaceOpt opt(getCtx()); + opt(); +} + +NEXTPNR_NAMESPACE_END |