xbar.cc revision 14192
16691Stjones1@inf.ed.ac.uk/* 26691Stjones1@inf.ed.ac.uk * Copyright (c) 2011-2015, 2018 ARM Limited 36691Stjones1@inf.ed.ac.uk * All rights reserved 46691Stjones1@inf.ed.ac.uk * 56691Stjones1@inf.ed.ac.uk * The license below extends only to copyright in the software and shall 66691Stjones1@inf.ed.ac.uk * not be construed as granting a license to any other intellectual 76691Stjones1@inf.ed.ac.uk * property including but not limited to intellectual property relating 86691Stjones1@inf.ed.ac.uk * to a hardware implementation of the functionality of the software 96691Stjones1@inf.ed.ac.uk * licensed hereunder. You may use the software subject to the license 106691Stjones1@inf.ed.ac.uk * terms below provided that you ensure that this notice is replicated 116691Stjones1@inf.ed.ac.uk * unmodified and in its entirety in all distributions of the software, 126691Stjones1@inf.ed.ac.uk * modified or unmodified, in source code or in binary form. 136691Stjones1@inf.ed.ac.uk * 146691Stjones1@inf.ed.ac.uk * Copyright (c) 2006 The Regents of The University of Michigan 156691Stjones1@inf.ed.ac.uk * All rights reserved. 166691Stjones1@inf.ed.ac.uk * 176691Stjones1@inf.ed.ac.uk * Redistribution and use in source and binary forms, with or without 186691Stjones1@inf.ed.ac.uk * modification, are permitted provided that the following conditions are 196691Stjones1@inf.ed.ac.uk * met: redistributions of source code must retain the above copyright 206691Stjones1@inf.ed.ac.uk * notice, this list of conditions and the following disclaimer; 216691Stjones1@inf.ed.ac.uk * redistributions in binary form must reproduce the above copyright 226691Stjones1@inf.ed.ac.uk * notice, this list of conditions and the following disclaimer in the 236691Stjones1@inf.ed.ac.uk * documentation and/or other materials provided with the distribution; 246691Stjones1@inf.ed.ac.uk * neither the name of the copyright holders nor the names of its 256691Stjones1@inf.ed.ac.uk * contributors may be used to endorse or promote products derived from 266691Stjones1@inf.ed.ac.uk * this software without specific prior written permission. 276691Stjones1@inf.ed.ac.uk * 286691Stjones1@inf.ed.ac.uk * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 296691Stjones1@inf.ed.ac.uk * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 306691Stjones1@inf.ed.ac.uk * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 316691Stjones1@inf.ed.ac.uk * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 326691Stjones1@inf.ed.ac.uk * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 336691Stjones1@inf.ed.ac.uk * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 346691Stjones1@inf.ed.ac.uk * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 356691Stjones1@inf.ed.ac.uk * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 366691Stjones1@inf.ed.ac.uk * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 376691Stjones1@inf.ed.ac.uk * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 386691Stjones1@inf.ed.ac.uk * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 396691Stjones1@inf.ed.ac.uk * 406691Stjones1@inf.ed.ac.uk * Authors: Ali Saidi 416691Stjones1@inf.ed.ac.uk * Andreas Hansson 426691Stjones1@inf.ed.ac.uk * William Wang 436691Stjones1@inf.ed.ac.uk */ 446691Stjones1@inf.ed.ac.uk 456691Stjones1@inf.ed.ac.uk/** 466691Stjones1@inf.ed.ac.uk * @file 476691Stjones1@inf.ed.ac.uk * Definition of a crossbar object. 486691Stjones1@inf.ed.ac.uk */ 496691Stjones1@inf.ed.ac.uk 506691Stjones1@inf.ed.ac.uk#include "mem/xbar.hh" 516691Stjones1@inf.ed.ac.uk 526691Stjones1@inf.ed.ac.uk#include "base/logging.hh" 536691Stjones1@inf.ed.ac.uk#include "base/trace.hh" 546691Stjones1@inf.ed.ac.uk#include "debug/AddrRanges.hh" 556691Stjones1@inf.ed.ac.uk#include "debug/Drain.hh" 566691Stjones1@inf.ed.ac.uk#include "debug/XBar.hh" 576691Stjones1@inf.ed.ac.uk 586691Stjones1@inf.ed.ac.ukBaseXBar::BaseXBar(const BaseXBarParams *p) 596691Stjones1@inf.ed.ac.uk : ClockedObject(p), 606691Stjones1@inf.ed.ac.uk frontendLatency(p->frontend_latency), 616691Stjones1@inf.ed.ac.uk forwardLatency(p->forward_latency), 6212104Snathanael.premillieu@arm.com responseLatency(p->response_latency), 636691Stjones1@inf.ed.ac.uk width(p->width), 646691Stjones1@inf.ed.ac.uk gotAddrRanges(p->port_default_connection_count + 656691Stjones1@inf.ed.ac.uk p->port_master_connection_count, false), 667720Sgblack@eecs.umich.edu gotAllAddrRanges(false), defaultPortID(InvalidPortID), 677720Sgblack@eecs.umich.edu useDefaultRange(p->use_default_range) 687720Sgblack@eecs.umich.edu{} 697720Sgblack@eecs.umich.edu 707720Sgblack@eecs.umich.eduBaseXBar::~BaseXBar() 717720Sgblack@eecs.umich.edu{ 7212614Sgabeblack@google.com for (auto m: masterPorts) 7312614Sgabeblack@google.com delete m; 7412614Sgabeblack@google.com 7512614Sgabeblack@google.com for (auto s: slavePorts) 7612614Sgabeblack@google.com delete s; 7712614Sgabeblack@google.com} 786691Stjones1@inf.ed.ac.uk 796691Stjones1@inf.ed.ac.ukPort & 807811Ssteve.reinhardt@amd.comBaseXBar::getPort(const std::string &if_name, PortID idx) 816691Stjones1@inf.ed.ac.uk{ 826691Stjones1@inf.ed.ac.uk if (if_name == "master" && idx < masterPorts.size()) { 83 // the master port index translates directly to the vector position 84 return *masterPorts[idx]; 85 } else if (if_name == "default") { 86 return *masterPorts[defaultPortID]; 87 } else if (if_name == "slave" && idx < slavePorts.size()) { 88 // the slave port index translates directly to the vector position 89 return *slavePorts[idx]; 90 } else { 91 return ClockedObject::getPort(if_name, idx); 92 } 93} 94 95void 96BaseXBar::calcPacketTiming(PacketPtr pkt, Tick header_delay) 97{ 98 // the crossbar will be called at a time that is not necessarily 99 // coinciding with its own clock, so start by determining how long 100 // until the next clock edge (could be zero) 101 Tick offset = clockEdge() - curTick(); 102 103 // the header delay depends on the path through the crossbar, and 104 // we therefore rely on the caller to provide the actual 105 // value 106 pkt->headerDelay += offset + header_delay; 107 108 // note that we add the header delay to the existing value, and 109 // align it to the crossbar clock 110 111 // do a quick sanity check to ensure the timings are not being 112 // ignored, note that this specific value may cause problems for 113 // slower interconnects 114 panic_if(pkt->headerDelay > SimClock::Int::us, 115 "Encountered header delay exceeding 1 us\n"); 116 117 if (pkt->hasData()) { 118 // the payloadDelay takes into account the relative time to 119 // deliver the payload of the packet, after the header delay, 120 // we take the maximum since the payload delay could already 121 // be longer than what this parcitular crossbar enforces. 122 pkt->payloadDelay = std::max<Tick>(pkt->payloadDelay, 123 divCeil(pkt->getSize(), width) * 124 clockPeriod()); 125 } 126 127 // the payload delay is not paying for the clock offset as that is 128 // already done using the header delay, and the payload delay is 129 // also used to determine how long the crossbar layer is busy and 130 // thus regulates throughput 131} 132 133template <typename SrcType, typename DstType> 134BaseXBar::Layer<SrcType, DstType>::Layer(DstType& _port, BaseXBar& _xbar, 135 const std::string& _name) : 136 port(_port), xbar(_xbar), _name(_name), state(IDLE), 137 waitingForPeer(NULL), releaseEvent([this]{ releaseLayer(); }, name()) 138{ 139} 140 141template <typename SrcType, typename DstType> 142void BaseXBar::Layer<SrcType, DstType>::occupyLayer(Tick until) 143{ 144 // ensure the state is busy at this point, as the layer should 145 // transition from idle as soon as it has decided to forward the 146 // packet to prevent any follow-on calls to sendTiming seeing an 147 // unoccupied layer 148 assert(state == BUSY); 149 150 // until should never be 0 as express snoops never occupy the layer 151 assert(until != 0); 152 xbar.schedule(releaseEvent, until); 153 154 // account for the occupied ticks 155 occupancy += until - curTick(); 156 157 DPRINTF(BaseXBar, "The crossbar layer is now busy from tick %d to %d\n", 158 curTick(), until); 159} 160 161template <typename SrcType, typename DstType> 162bool 163BaseXBar::Layer<SrcType, DstType>::tryTiming(SrcType* src_port) 164{ 165 // if we are in the retry state, we will not see anything but the 166 // retrying port (or in the case of the snoop ports the snoop 167 // response port that mirrors the actual slave port) as we leave 168 // this state again in zero time if the peer does not immediately 169 // call the layer when receiving the retry 170 171 // first we see if the layer is busy, next we check if the 172 // destination port is already engaged in a transaction waiting 173 // for a retry from the peer 174 if (state == BUSY || waitingForPeer != NULL) { 175 // the port should not be waiting already 176 assert(std::find(waitingForLayer.begin(), waitingForLayer.end(), 177 src_port) == waitingForLayer.end()); 178 179 // put the port at the end of the retry list waiting for the 180 // layer to be freed up (and in the case of a busy peer, for 181 // that transaction to go through, and then the layer to free 182 // up) 183 waitingForLayer.push_back(src_port); 184 return false; 185 } 186 187 state = BUSY; 188 189 return true; 190} 191 192template <typename SrcType, typename DstType> 193void 194BaseXBar::Layer<SrcType, DstType>::succeededTiming(Tick busy_time) 195{ 196 // we should have gone from idle or retry to busy in the tryTiming 197 // test 198 assert(state == BUSY); 199 200 // occupy the layer accordingly 201 occupyLayer(busy_time); 202} 203 204template <typename SrcType, typename DstType> 205void 206BaseXBar::Layer<SrcType, DstType>::failedTiming(SrcType* src_port, 207 Tick busy_time) 208{ 209 // ensure no one got in between and tried to send something to 210 // this port 211 assert(waitingForPeer == NULL); 212 213 // if the source port is the current retrying one or not, we have 214 // failed in forwarding and should track that we are now waiting 215 // for the peer to send a retry 216 waitingForPeer = src_port; 217 218 // we should have gone from idle or retry to busy in the tryTiming 219 // test 220 assert(state == BUSY); 221 222 // occupy the bus accordingly 223 occupyLayer(busy_time); 224} 225 226template <typename SrcType, typename DstType> 227void 228BaseXBar::Layer<SrcType, DstType>::releaseLayer() 229{ 230 // releasing the bus means we should now be idle 231 assert(state == BUSY); 232 assert(!releaseEvent.scheduled()); 233 234 // update the state 235 state = IDLE; 236 237 // bus layer is now idle, so if someone is waiting we can retry 238 if (!waitingForLayer.empty()) { 239 // there is no point in sending a retry if someone is still 240 // waiting for the peer 241 if (waitingForPeer == NULL) 242 retryWaiting(); 243 } else if (waitingForPeer == NULL && drainState() == DrainState::Draining) { 244 DPRINTF(Drain, "Crossbar done draining, signaling drain manager\n"); 245 //If we weren't able to drain before, do it now. 246 signalDrainDone(); 247 } 248} 249 250template <typename SrcType, typename DstType> 251void 252BaseXBar::Layer<SrcType, DstType>::retryWaiting() 253{ 254 // this should never be called with no one waiting 255 assert(!waitingForLayer.empty()); 256 257 // we always go to retrying from idle 258 assert(state == IDLE); 259 260 // update the state 261 state = RETRY; 262 263 // set the retrying port to the front of the retry list and pop it 264 // off the list 265 SrcType* retryingPort = waitingForLayer.front(); 266 waitingForLayer.pop_front(); 267 268 // tell the port to retry, which in some cases ends up calling the 269 // layer again 270 sendRetry(retryingPort); 271 272 // If the layer is still in the retry state, sendTiming wasn't 273 // called in zero time (e.g. the cache does this when a writeback 274 // is squashed) 275 if (state == RETRY) { 276 // update the state to busy and reset the retrying port, we 277 // have done our bit and sent the retry 278 state = BUSY; 279 280 // occupy the crossbar layer until the next clock edge 281 occupyLayer(xbar.clockEdge()); 282 } 283} 284 285template <typename SrcType, typename DstType> 286void 287BaseXBar::Layer<SrcType, DstType>::recvRetry() 288{ 289 // we should never get a retry without having failed to forward 290 // something to this port 291 assert(waitingForPeer != NULL); 292 293 // add the port where the failed packet originated to the front of 294 // the waiting ports for the layer, this allows us to call retry 295 // on the port immediately if the crossbar layer is idle 296 waitingForLayer.push_front(waitingForPeer); 297 298 // we are no longer waiting for the peer 299 waitingForPeer = NULL; 300 301 // if the layer is idle, retry this port straight away, if we 302 // are busy, then simply let the port wait for its turn 303 if (state == IDLE) { 304 retryWaiting(); 305 } else { 306 assert(state == BUSY); 307 } 308} 309 310PortID 311BaseXBar::findPort(AddrRange addr_range) 312{ 313 // we should never see any address lookups before we've got the 314 // ranges of all connected slave modules 315 assert(gotAllAddrRanges); 316 317 // Check the address map interval tree 318 auto i = portMap.contains(addr_range); 319 if (i != portMap.end()) { 320 return i->second; 321 } 322 323 // Check if this matches the default range 324 if (useDefaultRange) { 325 if (addr_range.isSubset(defaultRange)) { 326 DPRINTF(AddrRanges, " found addr %s on default\n", 327 addr_range.to_string()); 328 return defaultPortID; 329 } 330 } else if (defaultPortID != InvalidPortID) { 331 DPRINTF(AddrRanges, "Unable to find destination for %s, " 332 "will use default port\n", addr_range.to_string()); 333 return defaultPortID; 334 } 335 336 // we should use the range for the default port and it did not 337 // match, or the default port is not set 338 fatal("Unable to find destination for %s on %s\n", addr_range.to_string(), 339 name()); 340} 341 342/** Function called by the port when the crossbar is receiving a range change.*/ 343void 344BaseXBar::recvRangeChange(PortID master_port_id) 345{ 346 DPRINTF(AddrRanges, "Received range change from slave port %s\n", 347 masterPorts[master_port_id]->getPeer()); 348 349 // remember that we got a range from this master port and thus the 350 // connected slave module 351 gotAddrRanges[master_port_id] = true; 352 353 // update the global flag 354 if (!gotAllAddrRanges) { 355 // take a logical AND of all the ports and see if we got 356 // ranges from everyone 357 gotAllAddrRanges = true; 358 std::vector<bool>::const_iterator r = gotAddrRanges.begin(); 359 while (gotAllAddrRanges && r != gotAddrRanges.end()) { 360 gotAllAddrRanges &= *r++; 361 } 362 if (gotAllAddrRanges) 363 DPRINTF(AddrRanges, "Got address ranges from all slaves\n"); 364 } 365 366 // note that we could get the range from the default port at any 367 // point in time, and we cannot assume that the default range is 368 // set before the other ones are, so we do additional checks once 369 // all ranges are provided 370 if (master_port_id == defaultPortID) { 371 // only update if we are indeed checking ranges for the 372 // default port since the port might not have a valid range 373 // otherwise 374 if (useDefaultRange) { 375 AddrRangeList ranges = masterPorts[master_port_id]->getAddrRanges(); 376 377 if (ranges.size() != 1) 378 fatal("Crossbar %s may only have a single default range", 379 name()); 380 381 defaultRange = ranges.front(); 382 } 383 } else { 384 // the ports are allowed to update their address ranges 385 // dynamically, so remove any existing entries 386 if (gotAddrRanges[master_port_id]) { 387 for (auto p = portMap.begin(); p != portMap.end(); ) { 388 if (p->second == master_port_id) 389 // erasing invalidates the iterator, so advance it 390 // before the deletion takes place 391 portMap.erase(p++); 392 else 393 p++; 394 } 395 } 396 397 AddrRangeList ranges = masterPorts[master_port_id]->getAddrRanges(); 398 399 for (const auto& r: ranges) { 400 DPRINTF(AddrRanges, "Adding range %s for id %d\n", 401 r.to_string(), master_port_id); 402 if (portMap.insert(r, master_port_id) == portMap.end()) { 403 PortID conflict_id = portMap.intersects(r)->second; 404 fatal("%s has two ports responding within range " 405 "%s:\n\t%s\n\t%s\n", 406 name(), 407 r.to_string(), 408 masterPorts[master_port_id]->getPeer(), 409 masterPorts[conflict_id]->getPeer()); 410 } 411 } 412 } 413 414 // if we have received ranges from all our neighbouring slave 415 // modules, go ahead and tell our connected master modules in 416 // turn, this effectively assumes a tree structure of the system 417 if (gotAllAddrRanges) { 418 DPRINTF(AddrRanges, "Aggregating address ranges\n"); 419 xbarRanges.clear(); 420 421 // start out with the default range 422 if (useDefaultRange) { 423 if (!gotAddrRanges[defaultPortID]) 424 fatal("Crossbar %s uses default range, but none provided", 425 name()); 426 427 xbarRanges.push_back(defaultRange); 428 DPRINTF(AddrRanges, "-- Adding default %s\n", 429 defaultRange.to_string()); 430 } 431 432 // merge all interleaved ranges and add any range that is not 433 // a subset of the default range 434 std::vector<AddrRange> intlv_ranges; 435 for (const auto& r: portMap) { 436 // if the range is interleaved then save it for now 437 if (r.first.interleaved()) { 438 // if we already got interleaved ranges that are not 439 // part of the same range, then first do a merge 440 // before we add the new one 441 if (!intlv_ranges.empty() && 442 !intlv_ranges.back().mergesWith(r.first)) { 443 DPRINTF(AddrRanges, "-- Merging range from %d ranges\n", 444 intlv_ranges.size()); 445 AddrRange merged_range(intlv_ranges); 446 // next decide if we keep the merged range or not 447 if (!(useDefaultRange && 448 merged_range.isSubset(defaultRange))) { 449 xbarRanges.push_back(merged_range); 450 DPRINTF(AddrRanges, "-- Adding merged range %s\n", 451 merged_range.to_string()); 452 } 453 intlv_ranges.clear(); 454 } 455 intlv_ranges.push_back(r.first); 456 } else { 457 // keep the current range if not a subset of the default 458 if (!(useDefaultRange && 459 r.first.isSubset(defaultRange))) { 460 xbarRanges.push_back(r.first); 461 DPRINTF(AddrRanges, "-- Adding range %s\n", 462 r.first.to_string()); 463 } 464 } 465 } 466 467 // if there is still interleaved ranges waiting to be merged, 468 // go ahead and do it 469 if (!intlv_ranges.empty()) { 470 DPRINTF(AddrRanges, "-- Merging range from %d ranges\n", 471 intlv_ranges.size()); 472 AddrRange merged_range(intlv_ranges); 473 if (!(useDefaultRange && merged_range.isSubset(defaultRange))) { 474 xbarRanges.push_back(merged_range); 475 DPRINTF(AddrRanges, "-- Adding merged range %s\n", 476 merged_range.to_string()); 477 } 478 } 479 480 // also check that no range partially intersects with the 481 // default range, this has to be done after all ranges are set 482 // as there are no guarantees for when the default range is 483 // update with respect to the other ones 484 if (useDefaultRange) { 485 for (const auto& r: xbarRanges) { 486 // see if the new range is partially 487 // overlapping the default range 488 if (r.intersects(defaultRange) && 489 !r.isSubset(defaultRange)) 490 fatal("Range %s intersects the " \ 491 "default range of %s but is not a " \ 492 "subset\n", r.to_string(), name()); 493 } 494 } 495 496 // tell all our neighbouring master ports that our address 497 // ranges have changed 498 for (const auto& s: slavePorts) 499 s->sendRangeChange(); 500 } 501} 502 503AddrRangeList 504BaseXBar::getAddrRanges() const 505{ 506 // we should never be asked without first having sent a range 507 // change, and the latter is only done once we have all the ranges 508 // of the connected devices 509 assert(gotAllAddrRanges); 510 511 // at the moment, this never happens, as there are no cycles in 512 // the range queries and no devices on the master side of a crossbar 513 // (CPU, cache, bridge etc) actually care about the ranges of the 514 // ports they are connected to 515 516 DPRINTF(AddrRanges, "Received address range request\n"); 517 518 return xbarRanges; 519} 520 521void 522BaseXBar::regStats() 523{ 524 ClockedObject::regStats(); 525 526 using namespace Stats; 527 528 transDist 529 .init(MemCmd::NUM_MEM_CMDS) 530 .name(name() + ".trans_dist") 531 .desc("Transaction distribution") 532 .flags(nozero); 533 534 // get the string representation of the commands 535 for (int i = 0; i < MemCmd::NUM_MEM_CMDS; i++) { 536 MemCmd cmd(i); 537 const std::string &cstr = cmd.toString(); 538 transDist.subname(i, cstr); 539 } 540 541 pktCount 542 .init(slavePorts.size(), masterPorts.size()) 543 .name(name() + ".pkt_count") 544 .desc("Packet count per connected master and slave (bytes)") 545 .flags(total | nozero | nonan); 546 547 pktSize 548 .init(slavePorts.size(), masterPorts.size()) 549 .name(name() + ".pkt_size") 550 .desc("Cumulative packet size per connected master and slave (bytes)") 551 .flags(total | nozero | nonan); 552 553 // both the packet count and total size are two-dimensional 554 // vectors, indexed by slave port id and master port id, thus the 555 // neighbouring master and slave, they do not differentiate what 556 // came from the master and was forwarded to the slave (requests 557 // and snoop responses) and what came from the slave and was 558 // forwarded to the master (responses and snoop requests) 559 for (int i = 0; i < slavePorts.size(); i++) { 560 pktCount.subname(i, slavePorts[i]->getPeer().name()); 561 pktSize.subname(i, slavePorts[i]->getPeer().name()); 562 for (int j = 0; j < masterPorts.size(); j++) { 563 pktCount.ysubname(j, masterPorts[j]->getPeer().name()); 564 pktSize.ysubname(j, masterPorts[j]->getPeer().name()); 565 } 566 } 567} 568 569template <typename SrcType, typename DstType> 570DrainState 571BaseXBar::Layer<SrcType, DstType>::drain() 572{ 573 //We should check that we're not "doing" anything, and that noone is 574 //waiting. We might be idle but have someone waiting if the device we 575 //contacted for a retry didn't actually retry. 576 if (state != IDLE) { 577 DPRINTF(Drain, "Crossbar not drained\n"); 578 return DrainState::Draining; 579 } else { 580 return DrainState::Drained; 581 } 582} 583 584template <typename SrcType, typename DstType> 585void 586BaseXBar::Layer<SrcType, DstType>::regStats() 587{ 588 using namespace Stats; 589 590 occupancy 591 .name(name() + ".occupancy") 592 .desc("Layer occupancy (ticks)") 593 .flags(nozero); 594 595 utilization 596 .name(name() + ".utilization") 597 .desc("Layer utilization (%)") 598 .precision(1) 599 .flags(nozero); 600 601 utilization = 100 * occupancy / simTicks; 602} 603 604/** 605 * Crossbar layer template instantiations. Could be removed with _impl.hh 606 * file, but since there are only two given options (MasterPort and 607 * SlavePort) it seems a bit excessive at this point. 608 */ 609template class BaseXBar::Layer<SlavePort, MasterPort>; 610template class BaseXBar::Layer<MasterPort, SlavePort>; 611