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/*
* nextpnr -- Next Generation Place and Route
*
* Copyright (C) 2020 gatecat <gatecat@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;
TimingAnalyser tmg;
NexusPostPlaceOpt(Context *ctx) : ctx(ctx), tmg(ctx){};
inline bool is_constrained(CellInfo *cell) { return cell->cluster != ClusterId(); }
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 : ctx->cells) {
// Search for FF cells
CellInfo *ff = cell.second.get();
if (ff->type != id_OXIDE_FF)
continue;
// Check M ('fabric') input net
NetInfo *m = ff->getPort(id_M);
if (m == nullptr)
continue;
// Ignore FFs that need both DI and M (PRLD mode)
if (ff->getPort(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 && dest_ff_cell->getPort(id_DI) != nullptr)
continue;
// Attempt the swap
bool swap_result = swap_cell_placement(ff, dest_ff);
if (!swap_result)
continue;
}
// Use direct interconnect
ff->renamePort(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()()
{
tmg.setup();
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
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