1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
|
/*
* nextpnr -- Next Generation Place and Route
*
* Copyright (C) 2018 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 "place_common.h"
#include <cmath>
#include "log.h"
#include "util.h"
NEXTPNR_NAMESPACE_BEGIN
// Get the total estimated wirelength for a net
wirelen_t get_net_metric(const Context *ctx, const NetInfo *net, MetricType type, float &tns)
{
wirelen_t wirelength = 0;
Loc driver_loc;
bool driver_gb;
CellInfo *driver_cell = net->driver.cell;
if (!driver_cell)
return 0;
if (driver_cell->bel == BelId())
return 0;
driver_gb = ctx->getBelGlobalBuf(driver_cell->bel);
driver_loc = ctx->getBelLocation(driver_cell->bel);
if (driver_gb)
return 0;
delay_t negative_slack = 0;
delay_t worst_slack = std::numeric_limits<delay_t>::max();
int xmin = driver_loc.x, xmax = driver_loc.x, ymin = driver_loc.y, ymax = driver_loc.y;
for (auto load : net->users) {
if (load.cell == nullptr)
continue;
CellInfo *load_cell = load.cell;
if (load_cell->bel == BelId())
continue;
if (ctx->timing_driven && type == MetricType::COST) {
delay_t net_delay = ctx->predictDelay(net, load);
auto slack = load.budget - net_delay;
if (slack < 0)
negative_slack += slack;
worst_slack = std::min(slack, worst_slack);
}
if (ctx->getBelGlobalBuf(load_cell->bel))
continue;
Loc load_loc = ctx->getBelLocation(load_cell->bel);
xmin = std::min(xmin, load_loc.x);
ymin = std::min(ymin, load_loc.y);
xmax = std::max(xmax, load_loc.x);
ymax = std::max(ymax, load_loc.y);
}
if (ctx->timing_driven && type == MetricType::COST) {
wirelength = wirelen_t(
(((ymax - ymin) + (xmax - xmin)) * std::min(5.0, (1.0 + std::exp(-ctx->getDelayNS(worst_slack) / 5)))));
} else {
wirelength = wirelen_t((ymax - ymin) + (xmax - xmin));
}
tns += ctx->getDelayNS(negative_slack);
return wirelength;
}
// Get the total wirelength for a cell
wirelen_t get_cell_metric(const Context *ctx, const CellInfo *cell, MetricType type)
{
std::set<IdString> nets;
for (auto p : cell->ports) {
if (p.second.net)
nets.insert(p.second.net->name);
}
wirelen_t wirelength = 0;
float tns = 0;
for (auto n : nets) {
wirelength += get_net_metric(ctx, ctx->nets.at(n).get(), type, tns);
}
return wirelength;
}
wirelen_t get_cell_metric_at_bel(const Context *ctx, CellInfo *cell, BelId bel, MetricType type)
{
BelId oldBel = cell->bel;
cell->bel = bel;
wirelen_t wirelen = get_cell_metric(ctx, cell, type);
cell->bel = oldBel;
return wirelen;
}
// Placing a single cell
bool place_single_cell(Context *ctx, CellInfo *cell, bool require_legality)
{
bool all_placed = false;
int iters = 25;
while (!all_placed) {
BelId best_bel = BelId();
wirelen_t best_wirelen = std::numeric_limits<wirelen_t>::max(),
best_ripup_wirelen = std::numeric_limits<wirelen_t>::max();
CellInfo *ripup_target = nullptr;
BelId ripup_bel = BelId();
if (cell->bel != BelId()) {
ctx->unbindBel(cell->bel);
}
BelType targetType = ctx->belTypeFromId(cell->type);
for (auto bel : ctx->getBels()) {
if (ctx->getBelType(bel) == targetType && (!require_legality || ctx->isValidBelForCell(cell, bel))) {
if (ctx->checkBelAvail(bel)) {
wirelen_t wirelen = get_cell_metric_at_bel(ctx, cell, bel, MetricType::COST);
if (iters >= 4)
wirelen += ctx->rng(25);
if (wirelen <= best_wirelen) {
best_wirelen = wirelen;
best_bel = bel;
}
} else {
wirelen_t wirelen = get_cell_metric_at_bel(ctx, cell, bel, MetricType::COST);
if (iters >= 4)
wirelen += ctx->rng(25);
if (wirelen <= best_ripup_wirelen) {
CellInfo *curr_cell = ctx->cells.at(ctx->getBoundBelCell(bel)).get();
if (curr_cell->belStrength < STRENGTH_STRONG) {
best_ripup_wirelen = wirelen;
ripup_bel = bel;
ripup_target = curr_cell;
}
}
}
}
}
if (best_bel == BelId()) {
if (iters == 0) {
log_error("failed to place cell '%s' of type '%s' (ripup iteration limit exceeded)\n",
cell->name.c_str(ctx), cell->type.c_str(ctx));
}
if (ripup_bel == BelId()) {
log_error("failed to place cell '%s' of type '%s'\n", cell->name.c_str(ctx), cell->type.c_str(ctx));
}
--iters;
ctx->unbindBel(ripup_target->bel);
best_bel = ripup_bel;
} else {
all_placed = true;
}
if (ctx->verbose)
log_info(" placed single cell '%s' at '%s'\n", cell->name.c_str(ctx),
ctx->getBelName(best_bel).c_str(ctx));
ctx->bindBel(best_bel, cell->name, STRENGTH_WEAK);
cell = ripup_target;
}
return true;
}
class ConstraintLegaliseWorker
{
private:
Context *ctx;
std::set<IdString> rippedCells;
std::unordered_map<IdString, Loc> oldLocations;
class IncreasingDiameterSearch
{
public:
IncreasingDiameterSearch() : start(0), min(0), max(-1){};
IncreasingDiameterSearch(int x) : start(x), min(x), max(x){};
IncreasingDiameterSearch(int start, int min, int max) : start(start), min(min), max(max){};
bool done() const { return (diameter > (max - min)); };
int get() const
{
int val = start + sign * diameter;
val = std::max(val, min);
val = std::min(val, max);
return val;
}
void next()
{
if (sign == 0) {
sign = 1;
diameter = 1;
} else if (sign == -1) {
sign = 1;
if ((start + sign * diameter) > max)
sign = -1;
++diameter;
} else {
sign = -1;
if ((start + sign * diameter) < min) {
sign = 1;
++diameter;
}
}
}
void reset()
{
sign = 0;
diameter = 0;
}
private:
int start, min, max;
int diameter = 0;
int sign = 0;
};
typedef std::unordered_map<IdString, Loc> CellLocations;
// Check if a location would be suitable for a cell and all its constrained children
// This also makes a crude attempt to "solve" unconstrained constraints, that is slow and horrible
// and will need to be reworked if mixed constrained/unconstrained chains become common
bool valid_loc_for(const CellInfo *cell, Loc loc, CellLocations &solution, std::unordered_set<Loc> &usedLocations)
{
BelId locBel = ctx->getBelByLocation(loc);
if (locBel == BelId()) {
return false;
}
if (ctx->getBelType(locBel) != ctx->belTypeFromId(cell->type)) {
return false;
}
if (!ctx->checkBelAvail(locBel)) {
IdString confCell = ctx->getConflictingBelCell(locBel);
if (ctx->cells[confCell]->belStrength >= STRENGTH_STRONG) {
return false;
}
}
usedLocations.insert(loc);
for (auto child : cell->constr_children) {
IncreasingDiameterSearch xSearch, ySearch, zSearch;
if (child->constr_x == child->UNCONSTR) {
xSearch = IncreasingDiameterSearch(loc.x, 0, ctx->getGridDimX() - 1);
} else {
xSearch = IncreasingDiameterSearch(loc.x + child->constr_x);
}
if (child->constr_y == child->UNCONSTR) {
ySearch = IncreasingDiameterSearch(loc.y, 0, ctx->getGridDimY() - 1);
} else {
ySearch = IncreasingDiameterSearch(loc.y + child->constr_y);
}
if (child->constr_z == child->UNCONSTR) {
zSearch = IncreasingDiameterSearch(loc.z, 0, ctx->getTileDimZ(loc.x, loc.y));
} else {
if (child->constr_abs_z) {
zSearch = IncreasingDiameterSearch(child->constr_z);
} else {
zSearch = IncreasingDiameterSearch(loc.z + child->constr_z);
}
}
bool success = false;
while (!xSearch.done()) {
Loc cloc;
cloc.x = xSearch.get();
cloc.y = ySearch.get();
cloc.z = zSearch.get();
zSearch.next();
if (zSearch.done()) {
zSearch.reset();
ySearch.next();
if (ySearch.done()) {
ySearch.reset();
xSearch.next();
}
}
if (usedLocations.count(cloc))
continue;
if (valid_loc_for(child, cloc, solution, usedLocations)) {
success = true;
break;
}
}
if (!success) {
usedLocations.erase(loc);
return false;
}
}
if (solution.count(cell->name))
usedLocations.erase(solution.at(cell->name));
solution[cell->name] = loc;
return true;
}
// Set the strength to locked on all cells in chain
void lockdown_chain(CellInfo *root)
{
root->belStrength = STRENGTH_LOCKED;
for (auto child : root->constr_children)
lockdown_chain(child);
}
// Legalise placement constraints on a cell
bool legalise_cell(CellInfo *cell)
{
if (cell->constr_parent != nullptr)
return true; // Only process chain roots
if (constraints_satisfied(cell)) {
if (cell->constr_children.size() > 0 || cell->constr_x != cell->UNCONSTR ||
cell->constr_y != cell->UNCONSTR || cell->constr_z != cell->UNCONSTR)
lockdown_chain(cell);
} else {
IncreasingDiameterSearch xRootSearch, yRootSearch, zRootSearch;
Loc currentLoc;
if (cell->bel != BelId())
currentLoc = ctx->getBelLocation(cell->bel);
else
currentLoc = oldLocations[cell->name];
if (cell->constr_x == cell->UNCONSTR)
xRootSearch = IncreasingDiameterSearch(currentLoc.x, 0, ctx->getGridDimX() - 1);
else
xRootSearch = IncreasingDiameterSearch(cell->constr_x);
if (cell->constr_y == cell->UNCONSTR)
yRootSearch = IncreasingDiameterSearch(currentLoc.y, 0, ctx->getGridDimY() - 1);
else
yRootSearch = IncreasingDiameterSearch(cell->constr_y);
if (cell->constr_z == cell->UNCONSTR)
zRootSearch = IncreasingDiameterSearch(currentLoc.z, 0, ctx->getTileDimZ(currentLoc.x, currentLoc.y));
else
zRootSearch = IncreasingDiameterSearch(cell->constr_z);
while (!xRootSearch.done()) {
Loc rootLoc;
rootLoc.x = xRootSearch.get();
rootLoc.y = yRootSearch.get();
rootLoc.z = zRootSearch.get();
zRootSearch.next();
if (zRootSearch.done()) {
zRootSearch.reset();
yRootSearch.next();
if (yRootSearch.done()) {
yRootSearch.reset();
xRootSearch.next();
}
}
CellLocations solution;
std::unordered_set<Loc> used;
if (valid_loc_for(cell, rootLoc, solution, used)) {
for (auto cp : solution) {
// First unbind all cells
if (ctx->cells.at(cp.first)->bel != BelId())
ctx->unbindBel(ctx->cells.at(cp.first)->bel);
}
for (auto cp : solution) {
if (ctx->verbose)
log_info(" placing '%s' at (%d, %d, %d)\n", cp.first.c_str(ctx), cp.second.x,
cp.second.y, cp.second.z);
BelId target = ctx->getBelByLocation(cp.second);
if (!ctx->checkBelAvail(target)) {
IdString conflicting = ctx->getConflictingBelCell(target);
if (conflicting != IdString()) {
CellInfo *confl_cell = ctx->cells.at(conflicting).get();
if (ctx->verbose)
log_info(" '%s' already placed at '%s'\n", conflicting.c_str(ctx),
ctx->getBelName(confl_cell->bel).c_str(ctx));
NPNR_ASSERT(confl_cell->belStrength < STRENGTH_STRONG);
ctx->unbindBel(target);
rippedCells.insert(conflicting);
}
}
ctx->bindBel(target, cp.first, STRENGTH_LOCKED);
rippedCells.erase(cp.first);
}
NPNR_ASSERT(constraints_satisfied(cell));
return true;
}
}
return false;
}
return true;
}
// Check if constraints are currently satisfied on a cell and its children
bool constraints_satisfied(const CellInfo *cell) { return get_constraints_distance(ctx, cell) == 0; }
public:
ConstraintLegaliseWorker(Context *ctx) : ctx(ctx){};
void print_chain(CellInfo *cell, int depth = 0)
{
for (int i = 0; i < depth; i++)
log(" ");
log("'%s' (", cell->name.c_str(ctx));
if (cell->constr_x != cell->UNCONSTR)
log("%d, ", cell->constr_x);
else
log("*, ");
if (cell->constr_y != cell->UNCONSTR)
log("%d, ", cell->constr_y);
else
log("*, ");
if (cell->constr_z != cell->UNCONSTR)
log("%d", cell->constr_z);
else
log("*");
log(")\n");
for (auto child : cell->constr_children)
print_chain(child, depth + 1);
}
void print_stats(const char *point)
{
float distance_sum = 0;
float max_distance = 0;
int moved_cells = 0;
int unplaced_cells = 0;
for (auto orig : oldLocations) {
if (ctx->cells.at(orig.first)->bel == BelId()) {
unplaced_cells++;
continue;
}
Loc newLoc = ctx->getBelLocation(ctx->cells.at(orig.first)->bel);
if (newLoc != orig.second) {
float distance = std::sqrt(std::pow(newLoc.x - orig.second.x, 2) + pow(newLoc.y - orig.second.y, 2));
moved_cells++;
distance_sum += distance;
if (distance > max_distance)
max_distance = distance;
}
}
log_info(" moved %d cells, %d unplaced (after %s)\n", moved_cells, unplaced_cells, point);
if (moved_cells > 0) {
log_info(" average distance %f\n", (distance_sum / moved_cells));
log_info(" maximum distance %f\n", max_distance);
}
}
bool legalise_constraints()
{
log_info("Legalising relative constraints...\n");
for (auto cell : sorted(ctx->cells)) {
oldLocations[cell.first] = ctx->getBelLocation(cell.second->bel);
}
for (auto cell : sorted(ctx->cells)) {
bool res = legalise_cell(cell.second);
if (!res) {
if (ctx->verbose)
print_chain(cell.second);
log_error("failed to place chain starting at cell '%s'\n", cell.first.c_str(ctx));
return false;
}
}
print_stats("after legalising chains");
for (auto rippedCell : rippedCells) {
bool res = place_single_cell(ctx, ctx->cells.at(rippedCell).get(), true);
if (!res) {
log_error("failed to place cell '%s' after relative constraint legalisation\n", rippedCell.c_str(ctx));
return false;
}
}
print_stats("after replacing ripped up cells");
for (auto cell : sorted(ctx->cells))
if (get_constraints_distance(ctx, cell.second) != 0)
log_error("constraint satisfaction check failed for cell '%s' at Bel '%s'\n", cell.first.c_str(ctx),
ctx->getBelName(cell.second->bel).c_str(ctx));
return true;
}
};
bool legalise_relative_constraints(Context *ctx) { return ConstraintLegaliseWorker(ctx).legalise_constraints(); }
// Get the total distance from satisfied constraints for a cell
int get_constraints_distance(const Context *ctx, const CellInfo *cell)
{
int dist = 0;
if (cell->bel == BelId())
return 100000;
Loc loc = ctx->getBelLocation(cell->bel);
if (cell->constr_parent == nullptr) {
if (cell->constr_x != cell->UNCONSTR)
dist += std::abs(cell->constr_x - loc.x);
if (cell->constr_y != cell->UNCONSTR)
dist += std::abs(cell->constr_y - loc.y);
if (cell->constr_z != cell->UNCONSTR)
dist += std::abs(cell->constr_z - loc.z);
} else {
if (cell->constr_parent->bel == BelId())
return 100000;
Loc parent_loc = ctx->getBelLocation(cell->constr_parent->bel);
if (cell->constr_x != cell->UNCONSTR)
dist += std::abs(cell->constr_x - (loc.x - parent_loc.x));
if (cell->constr_y != cell->UNCONSTR)
dist += std::abs(cell->constr_y - (loc.y - parent_loc.y));
if (cell->constr_z != cell->UNCONSTR) {
if (cell->constr_abs_z)
dist += std::abs(cell->constr_z - loc.z);
else
dist += std::abs(cell->constr_z - (loc.z - parent_loc.z));
}
}
for (auto child : cell->constr_children)
dist += get_constraints_distance(ctx, child);
return dist;
}
NEXTPNR_NAMESPACE_END
|