1 //===----- R600Packetizer.cpp - VLIW packetizer ---------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 /// \file
10 /// This pass implements instructions packetization for R600. It unsets isLast
11 /// bit of instructions inside a bundle and substitutes src register with
12 /// PreviousVector when applicable.
13 //
14 //===----------------------------------------------------------------------===//
15
16 #include "MCTargetDesc/R600MCTargetDesc.h"
17 #include "R600.h"
18 #include "R600Subtarget.h"
19 #include "llvm/CodeGen/DFAPacketizer.h"
20 #include "llvm/CodeGen/MachineDominators.h"
21 #include "llvm/CodeGen/MachineLoopInfo.h"
22 #include "llvm/CodeGen/ScheduleDAG.h"
23
24 using namespace llvm;
25
26 #define DEBUG_TYPE "packets"
27
28 namespace {
29
30 class R600Packetizer : public MachineFunctionPass {
31
32 public:
33 static char ID;
R600Packetizer()34 R600Packetizer() : MachineFunctionPass(ID) {}
35
getAnalysisUsage(AnalysisUsage & AU) const36 void getAnalysisUsage(AnalysisUsage &AU) const override {
37 AU.setPreservesCFG();
38 AU.addRequired<MachineDominatorTreeWrapperPass>();
39 AU.addPreserved<MachineDominatorTreeWrapperPass>();
40 AU.addRequired<MachineLoopInfoWrapperPass>();
41 AU.addPreserved<MachineLoopInfoWrapperPass>();
42 MachineFunctionPass::getAnalysisUsage(AU);
43 }
44
getPassName() const45 StringRef getPassName() const override { return "R600 Packetizer"; }
46
47 bool runOnMachineFunction(MachineFunction &Fn) override;
48 };
49
50 class R600PacketizerList : public VLIWPacketizerList {
51 private:
52 const R600InstrInfo *TII;
53 const R600RegisterInfo &TRI;
54 bool VLIW5;
55 bool ConsideredInstUsesAlreadyWrittenVectorElement;
56
getSlot(const MachineInstr & MI) const57 unsigned getSlot(const MachineInstr &MI) const {
58 return TRI.getHWRegChan(MI.getOperand(0).getReg());
59 }
60
61 /// \returns register to PV chan mapping for bundle/single instructions that
62 /// immediately precedes I.
getPreviousVector(MachineBasicBlock::iterator I) const63 DenseMap<unsigned, unsigned> getPreviousVector(MachineBasicBlock::iterator I)
64 const {
65 DenseMap<unsigned, unsigned> Result;
66 I--;
67 if (!TII->isALUInstr(I->getOpcode()) && !I->isBundle())
68 return Result;
69 MachineBasicBlock::instr_iterator BI = I.getInstrIterator();
70 if (I->isBundle())
71 BI++;
72 int LastDstChan = -1;
73 do {
74 bool isTrans = false;
75 int BISlot = getSlot(*BI);
76 if (LastDstChan >= BISlot)
77 isTrans = true;
78 LastDstChan = BISlot;
79 if (TII->isPredicated(*BI))
80 continue;
81 int OperandIdx = TII->getOperandIdx(BI->getOpcode(), R600::OpName::write);
82 if (OperandIdx > -1 && BI->getOperand(OperandIdx).getImm() == 0)
83 continue;
84 int DstIdx = TII->getOperandIdx(BI->getOpcode(), R600::OpName::dst);
85 if (DstIdx == -1) {
86 continue;
87 }
88 Register Dst = BI->getOperand(DstIdx).getReg();
89 if (isTrans || TII->isTransOnly(*BI)) {
90 Result[Dst] = R600::PS;
91 continue;
92 }
93 if (BI->getOpcode() == R600::DOT4_r600 ||
94 BI->getOpcode() == R600::DOT4_eg) {
95 Result[Dst] = R600::PV_X;
96 continue;
97 }
98 if (Dst == R600::OQAP) {
99 continue;
100 }
101 unsigned PVReg = 0;
102 switch (TRI.getHWRegChan(Dst)) {
103 case 0:
104 PVReg = R600::PV_X;
105 break;
106 case 1:
107 PVReg = R600::PV_Y;
108 break;
109 case 2:
110 PVReg = R600::PV_Z;
111 break;
112 case 3:
113 PVReg = R600::PV_W;
114 break;
115 default:
116 llvm_unreachable("Invalid Chan");
117 }
118 Result[Dst] = PVReg;
119 } while ((++BI)->isBundledWithPred());
120 return Result;
121 }
122
substitutePV(MachineInstr & MI,const DenseMap<unsigned,unsigned> & PVs) const123 void substitutePV(MachineInstr &MI, const DenseMap<unsigned, unsigned> &PVs)
124 const {
125 unsigned Ops[] = {
126 R600::OpName::src0,
127 R600::OpName::src1,
128 R600::OpName::src2
129 };
130 for (unsigned Op : Ops) {
131 int OperandIdx = TII->getOperandIdx(MI.getOpcode(), Op);
132 if (OperandIdx < 0)
133 continue;
134 Register Src = MI.getOperand(OperandIdx).getReg();
135 const DenseMap<unsigned, unsigned>::const_iterator It = PVs.find(Src);
136 if (It != PVs.end())
137 MI.getOperand(OperandIdx).setReg(It->second);
138 }
139 }
140 public:
141 // Ctor.
R600PacketizerList(MachineFunction & MF,const R600Subtarget & ST,MachineLoopInfo & MLI)142 R600PacketizerList(MachineFunction &MF, const R600Subtarget &ST,
143 MachineLoopInfo &MLI)
144 : VLIWPacketizerList(MF, MLI, nullptr),
145 TII(ST.getInstrInfo()),
146 TRI(TII->getRegisterInfo()) {
147 VLIW5 = !ST.hasCaymanISA();
148 }
149
150 // initPacketizerState - initialize some internal flags.
initPacketizerState()151 void initPacketizerState() override {
152 ConsideredInstUsesAlreadyWrittenVectorElement = false;
153 }
154
155 // ignorePseudoInstruction - Ignore bundling of pseudo instructions.
ignorePseudoInstruction(const MachineInstr & MI,const MachineBasicBlock * MBB)156 bool ignorePseudoInstruction(const MachineInstr &MI,
157 const MachineBasicBlock *MBB) override {
158 return false;
159 }
160
161 // isSoloInstruction - return true if instruction MI can not be packetized
162 // with any other instruction, which means that MI itself is a packet.
isSoloInstruction(const MachineInstr & MI)163 bool isSoloInstruction(const MachineInstr &MI) override {
164 if (TII->isVector(MI))
165 return true;
166 if (!TII->isALUInstr(MI.getOpcode()))
167 return true;
168 if (MI.getOpcode() == R600::GROUP_BARRIER)
169 return true;
170 // XXX: This can be removed once the packetizer properly handles all the
171 // LDS instruction group restrictions.
172 return TII->isLDSInstr(MI.getOpcode());
173 }
174
175 // isLegalToPacketizeTogether - Is it legal to packetize SUI and SUJ
176 // together.
isLegalToPacketizeTogether(SUnit * SUI,SUnit * SUJ)177 bool isLegalToPacketizeTogether(SUnit *SUI, SUnit *SUJ) override {
178 MachineInstr *MII = SUI->getInstr(), *MIJ = SUJ->getInstr();
179 if (getSlot(*MII) == getSlot(*MIJ))
180 ConsideredInstUsesAlreadyWrittenVectorElement = true;
181 // Does MII and MIJ share the same pred_sel ?
182 int OpI = TII->getOperandIdx(MII->getOpcode(), R600::OpName::pred_sel),
183 OpJ = TII->getOperandIdx(MIJ->getOpcode(), R600::OpName::pred_sel);
184 Register PredI = (OpI > -1)?MII->getOperand(OpI).getReg() : Register(),
185 PredJ = (OpJ > -1)?MIJ->getOperand(OpJ).getReg() : Register();
186 if (PredI != PredJ)
187 return false;
188 if (SUJ->isSucc(SUI)) {
189 for (const SDep &Dep : SUJ->Succs) {
190 if (Dep.getSUnit() != SUI)
191 continue;
192 if (Dep.getKind() == SDep::Anti)
193 continue;
194 if (Dep.getKind() == SDep::Output)
195 if (MII->getOperand(0).getReg() != MIJ->getOperand(0).getReg())
196 continue;
197 return false;
198 }
199 }
200
201 bool ARDef =
202 TII->definesAddressRegister(*MII) || TII->definesAddressRegister(*MIJ);
203 bool ARUse =
204 TII->usesAddressRegister(*MII) || TII->usesAddressRegister(*MIJ);
205
206 return !ARDef || !ARUse;
207 }
208
209 // isLegalToPruneDependencies - Is it legal to prune dependency between SUI
210 // and SUJ.
isLegalToPruneDependencies(SUnit * SUI,SUnit * SUJ)211 bool isLegalToPruneDependencies(SUnit *SUI, SUnit *SUJ) override {
212 return false;
213 }
214
setIsLastBit(MachineInstr * MI,unsigned Bit) const215 void setIsLastBit(MachineInstr *MI, unsigned Bit) const {
216 unsigned LastOp = TII->getOperandIdx(MI->getOpcode(), R600::OpName::last);
217 MI->getOperand(LastOp).setImm(Bit);
218 }
219
isBundlableWithCurrentPMI(MachineInstr & MI,const DenseMap<unsigned,unsigned> & PV,std::vector<R600InstrInfo::BankSwizzle> & BS,bool & isTransSlot)220 bool isBundlableWithCurrentPMI(MachineInstr &MI,
221 const DenseMap<unsigned, unsigned> &PV,
222 std::vector<R600InstrInfo::BankSwizzle> &BS,
223 bool &isTransSlot) {
224 isTransSlot = TII->isTransOnly(MI);
225 assert (!isTransSlot || VLIW5);
226
227 // Is the dst reg sequence legal ?
228 if (!isTransSlot && !CurrentPacketMIs.empty()) {
229 if (getSlot(MI) <= getSlot(*CurrentPacketMIs.back())) {
230 if (ConsideredInstUsesAlreadyWrittenVectorElement &&
231 !TII->isVectorOnly(MI) && VLIW5) {
232 isTransSlot = true;
233 LLVM_DEBUG({
234 dbgs() << "Considering as Trans Inst :";
235 MI.dump();
236 });
237 }
238 else
239 return false;
240 }
241 }
242
243 // Are the Constants limitations met ?
244 CurrentPacketMIs.push_back(&MI);
245 if (!TII->fitsConstReadLimitations(CurrentPacketMIs)) {
246 LLVM_DEBUG({
247 dbgs() << "Couldn't pack :\n";
248 MI.dump();
249 dbgs() << "with the following packets :\n";
250 for (unsigned i = 0, e = CurrentPacketMIs.size() - 1; i < e; i++) {
251 CurrentPacketMIs[i]->dump();
252 dbgs() << "\n";
253 }
254 dbgs() << "because of Consts read limitations\n";
255 });
256 CurrentPacketMIs.pop_back();
257 return false;
258 }
259
260 // Is there a BankSwizzle set that meet Read Port limitations ?
261 if (!TII->fitsReadPortLimitations(CurrentPacketMIs,
262 PV, BS, isTransSlot)) {
263 LLVM_DEBUG({
264 dbgs() << "Couldn't pack :\n";
265 MI.dump();
266 dbgs() << "with the following packets :\n";
267 for (unsigned i = 0, e = CurrentPacketMIs.size() - 1; i < e; i++) {
268 CurrentPacketMIs[i]->dump();
269 dbgs() << "\n";
270 }
271 dbgs() << "because of Read port limitations\n";
272 });
273 CurrentPacketMIs.pop_back();
274 return false;
275 }
276
277 // We cannot read LDS source registers from the Trans slot.
278 if (isTransSlot && TII->readsLDSSrcReg(MI))
279 return false;
280
281 CurrentPacketMIs.pop_back();
282 return true;
283 }
284
addToPacket(MachineInstr & MI)285 MachineBasicBlock::iterator addToPacket(MachineInstr &MI) override {
286 MachineBasicBlock::iterator FirstInBundle =
287 CurrentPacketMIs.empty() ? &MI : CurrentPacketMIs.front();
288 const DenseMap<unsigned, unsigned> &PV =
289 getPreviousVector(FirstInBundle);
290 std::vector<R600InstrInfo::BankSwizzle> BS;
291 bool isTransSlot;
292
293 if (isBundlableWithCurrentPMI(MI, PV, BS, isTransSlot)) {
294 for (unsigned i = 0, e = CurrentPacketMIs.size(); i < e; i++) {
295 MachineInstr *MI = CurrentPacketMIs[i];
296 unsigned Op = TII->getOperandIdx(MI->getOpcode(),
297 R600::OpName::bank_swizzle);
298 MI->getOperand(Op).setImm(BS[i]);
299 }
300 unsigned Op =
301 TII->getOperandIdx(MI.getOpcode(), R600::OpName::bank_swizzle);
302 MI.getOperand(Op).setImm(BS.back());
303 if (!CurrentPacketMIs.empty())
304 setIsLastBit(CurrentPacketMIs.back(), 0);
305 substitutePV(MI, PV);
306 MachineBasicBlock::iterator It = VLIWPacketizerList::addToPacket(MI);
307 if (isTransSlot) {
308 endPacket(std::next(It)->getParent(), std::next(It));
309 }
310 return It;
311 }
312 endPacket(MI.getParent(), MI);
313 if (TII->isTransOnly(MI))
314 return MI;
315 return VLIWPacketizerList::addToPacket(MI);
316 }
317 };
318
runOnMachineFunction(MachineFunction & Fn)319 bool R600Packetizer::runOnMachineFunction(MachineFunction &Fn) {
320 const R600Subtarget &ST = Fn.getSubtarget<R600Subtarget>();
321 const R600InstrInfo *TII = ST.getInstrInfo();
322
323 MachineLoopInfo &MLI = getAnalysis<MachineLoopInfoWrapperPass>().getLI();
324
325 // Instantiate the packetizer.
326 R600PacketizerList Packetizer(Fn, ST, MLI);
327
328 // DFA state table should not be empty.
329 assert(Packetizer.getResourceTracker() && "Empty DFA table!");
330 assert(Packetizer.getResourceTracker()->getInstrItins());
331
332 if (Packetizer.getResourceTracker()->getInstrItins()->isEmpty())
333 return false;
334
335 //
336 // Loop over all basic blocks and remove KILL pseudo-instructions
337 // These instructions confuse the dependence analysis. Consider:
338 // D0 = ... (Insn 0)
339 // R0 = KILL R0, D0 (Insn 1)
340 // R0 = ... (Insn 2)
341 // Here, Insn 1 will result in the dependence graph not emitting an output
342 // dependence between Insn 0 and Insn 2. This can lead to incorrect
343 // packetization
344 //
345 for (MachineBasicBlock &MBB : Fn) {
346 for (MachineInstr &MI : llvm::make_early_inc_range(MBB)) {
347 if (MI.isKill() || MI.getOpcode() == R600::IMPLICIT_DEF ||
348 (MI.getOpcode() == R600::CF_ALU && !MI.getOperand(8).getImm()))
349 MBB.erase(MI);
350 }
351 }
352
353 // Loop over all of the basic blocks.
354 for (MachineFunction::iterator MBB = Fn.begin(), MBBe = Fn.end();
355 MBB != MBBe; ++MBB) {
356 // Find scheduling regions and schedule / packetize each region.
357 unsigned RemainingCount = MBB->size();
358 for(MachineBasicBlock::iterator RegionEnd = MBB->end();
359 RegionEnd != MBB->begin();) {
360 // The next region starts above the previous region. Look backward in the
361 // instruction stream until we find the nearest boundary.
362 MachineBasicBlock::iterator I = RegionEnd;
363 for(;I != MBB->begin(); --I, --RemainingCount) {
364 if (TII->isSchedulingBoundary(*std::prev(I), &*MBB, Fn))
365 break;
366 }
367 I = MBB->begin();
368
369 // Skip empty scheduling regions.
370 if (I == RegionEnd) {
371 RegionEnd = std::prev(RegionEnd);
372 --RemainingCount;
373 continue;
374 }
375 // Skip regions with one instruction.
376 if (I == std::prev(RegionEnd)) {
377 RegionEnd = std::prev(RegionEnd);
378 continue;
379 }
380
381 Packetizer.PacketizeMIs(&*MBB, &*I, RegionEnd);
382 RegionEnd = I;
383 }
384 }
385
386 return true;
387
388 }
389
390 } // end anonymous namespace
391
392 INITIALIZE_PASS_BEGIN(R600Packetizer, DEBUG_TYPE,
393 "R600 Packetizer", false, false)
394 INITIALIZE_PASS_END(R600Packetizer, DEBUG_TYPE,
395 "R600 Packetizer", false, false)
396
397 char R600Packetizer::ID = 0;
398
399 char &llvm::R600PacketizerID = R600Packetizer::ID;
400
createR600Packetizer()401 llvm::FunctionPass *llvm::createR600Packetizer() {
402 return new R600Packetizer();
403 }
404