1 //===- R600MergeVectorRegisters.cpp ---------------------------------------===//
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 merges inputs of swizzeable instructions into vector sharing
11 /// common data and/or have enough undef subreg using swizzle abilities.
12 ///
13 /// For instance let's consider the following pseudo code :
14 /// %5 = REG_SEQ %1, sub0, %2, sub1, %3, sub2, undef, sub3
15 /// ...
16 /// %7 = REG_SEQ %1, sub0, %3, sub1, undef, sub2, %4, sub3
17 /// (swizzable Inst) %7, SwizzleMask : sub0, sub1, sub2, sub3
18 ///
19 /// is turned into :
20 /// %5 = REG_SEQ %1, sub0, %2, sub1, %3, sub2, undef, sub3
21 /// ...
22 /// %7 = INSERT_SUBREG %4, sub3
23 /// (swizzable Inst) %7, SwizzleMask : sub0, sub2, sub1, sub3
24 ///
25 /// This allow regalloc to reduce register pressure for vector registers and
26 /// to reduce MOV count.
27 //===----------------------------------------------------------------------===//
28
29 #include "MCTargetDesc/R600MCTargetDesc.h"
30 #include "R600.h"
31 #include "R600Defines.h"
32 #include "R600Subtarget.h"
33 #include "llvm/CodeGen/MachineDominators.h"
34 #include "llvm/CodeGen/MachineLoopInfo.h"
35
36 using namespace llvm;
37
38 #define DEBUG_TYPE "vec-merger"
39
isImplicitlyDef(MachineRegisterInfo & MRI,Register Reg)40 static bool isImplicitlyDef(MachineRegisterInfo &MRI, Register Reg) {
41 if (Reg.isPhysical())
42 return false;
43 const MachineInstr *MI = MRI.getUniqueVRegDef(Reg);
44 return MI && MI->isImplicitDef();
45 }
46
47 namespace {
48
49 class RegSeqInfo {
50 public:
51 MachineInstr *Instr;
52 DenseMap<Register, unsigned> RegToChan;
53 std::vector<Register> UndefReg;
54
RegSeqInfo(MachineRegisterInfo & MRI,MachineInstr * MI)55 RegSeqInfo(MachineRegisterInfo &MRI, MachineInstr *MI) : Instr(MI) {
56 assert(MI->getOpcode() == R600::REG_SEQUENCE);
57 for (unsigned i = 1, e = Instr->getNumOperands(); i < e; i+=2) {
58 MachineOperand &MO = Instr->getOperand(i);
59 unsigned Chan = Instr->getOperand(i + 1).getImm();
60 if (isImplicitlyDef(MRI, MO.getReg()))
61 UndefReg.emplace_back(Chan);
62 else
63 RegToChan[MO.getReg()] = Chan;
64 }
65 }
66
67 RegSeqInfo() = default;
68
operator ==(const RegSeqInfo & RSI) const69 bool operator==(const RegSeqInfo &RSI) const {
70 return RSI.Instr == Instr;
71 }
72 };
73
74 class R600VectorRegMerger : public MachineFunctionPass {
75 private:
76 using InstructionSetMap = DenseMap<unsigned, std::vector<MachineInstr *>>;
77
78 MachineRegisterInfo *MRI;
79 const R600InstrInfo *TII = nullptr;
80 DenseMap<MachineInstr *, RegSeqInfo> PreviousRegSeq;
81 InstructionSetMap PreviousRegSeqByReg;
82 InstructionSetMap PreviousRegSeqByUndefCount;
83
84 bool canSwizzle(const MachineInstr &MI) const;
85 bool areAllUsesSwizzeable(Register Reg) const;
86 void SwizzleInput(MachineInstr &,
87 const std::vector<std::pair<unsigned, unsigned>> &RemapChan) const;
88 bool tryMergeVector(const RegSeqInfo *Untouched, RegSeqInfo *ToMerge,
89 std::vector<std::pair<unsigned, unsigned>> &Remap) const;
90 bool tryMergeUsingCommonSlot(RegSeqInfo &RSI, RegSeqInfo &CompatibleRSI,
91 std::vector<std::pair<unsigned, unsigned>> &RemapChan);
92 bool tryMergeUsingFreeSlot(RegSeqInfo &RSI, RegSeqInfo &CompatibleRSI,
93 std::vector<std::pair<unsigned, unsigned>> &RemapChan);
94 MachineInstr *RebuildVector(RegSeqInfo *MI, const RegSeqInfo *BaseVec,
95 const std::vector<std::pair<unsigned, unsigned>> &RemapChan) const;
96 void RemoveMI(MachineInstr *);
97 void trackRSI(const RegSeqInfo &RSI);
98
99 public:
100 static char ID;
101
R600VectorRegMerger()102 R600VectorRegMerger() : MachineFunctionPass(ID) {}
103
getAnalysisUsage(AnalysisUsage & AU) const104 void getAnalysisUsage(AnalysisUsage &AU) const override {
105 AU.setPreservesCFG();
106 AU.addRequired<MachineDominatorTreeWrapperPass>();
107 AU.addPreserved<MachineDominatorTreeWrapperPass>();
108 AU.addRequired<MachineLoopInfoWrapperPass>();
109 AU.addPreserved<MachineLoopInfoWrapperPass>();
110 MachineFunctionPass::getAnalysisUsage(AU);
111 }
112
getRequiredProperties() const113 MachineFunctionProperties getRequiredProperties() const override {
114 return MachineFunctionProperties().setIsSSA();
115 }
116
getPassName() const117 StringRef getPassName() const override {
118 return "R600 Vector Registers Merge Pass";
119 }
120
121 bool runOnMachineFunction(MachineFunction &Fn) override;
122 };
123
124 } // end anonymous namespace
125
126 INITIALIZE_PASS_BEGIN(R600VectorRegMerger, DEBUG_TYPE,
127 "R600 Vector Reg Merger", false, false)
128 INITIALIZE_PASS_END(R600VectorRegMerger, DEBUG_TYPE,
129 "R600 Vector Reg Merger", false, false)
130
131 char R600VectorRegMerger::ID = 0;
132
133 char &llvm::R600VectorRegMergerID = R600VectorRegMerger::ID;
134
canSwizzle(const MachineInstr & MI) const135 bool R600VectorRegMerger::canSwizzle(const MachineInstr &MI)
136 const {
137 if (TII->get(MI.getOpcode()).TSFlags & R600_InstFlag::TEX_INST)
138 return true;
139 switch (MI.getOpcode()) {
140 case R600::R600_ExportSwz:
141 case R600::EG_ExportSwz:
142 return true;
143 default:
144 return false;
145 }
146 }
147
tryMergeVector(const RegSeqInfo * Untouched,RegSeqInfo * ToMerge,std::vector<std::pair<unsigned,unsigned>> & Remap) const148 bool R600VectorRegMerger::tryMergeVector(const RegSeqInfo *Untouched,
149 RegSeqInfo *ToMerge, std::vector< std::pair<unsigned, unsigned>> &Remap)
150 const {
151 unsigned CurrentUndexIdx = 0;
152 for (auto &It : ToMerge->RegToChan) {
153 DenseMap<Register, unsigned>::const_iterator PosInUntouched =
154 Untouched->RegToChan.find(It.first);
155 if (PosInUntouched != Untouched->RegToChan.end()) {
156 Remap.emplace_back(It.second, (*PosInUntouched).second);
157 continue;
158 }
159 if (CurrentUndexIdx >= Untouched->UndefReg.size())
160 return false;
161 Remap.emplace_back(It.second, Untouched->UndefReg[CurrentUndexIdx++]);
162 }
163
164 return true;
165 }
166
167 static
getReassignedChan(const std::vector<std::pair<unsigned,unsigned>> & RemapChan,unsigned Chan)168 unsigned getReassignedChan(
169 const std::vector<std::pair<unsigned, unsigned>> &RemapChan,
170 unsigned Chan) {
171 for (const auto &J : RemapChan) {
172 if (J.first == Chan)
173 return J.second;
174 }
175 llvm_unreachable("Chan wasn't reassigned");
176 }
177
RebuildVector(RegSeqInfo * RSI,const RegSeqInfo * BaseRSI,const std::vector<std::pair<unsigned,unsigned>> & RemapChan) const178 MachineInstr *R600VectorRegMerger::RebuildVector(
179 RegSeqInfo *RSI, const RegSeqInfo *BaseRSI,
180 const std::vector<std::pair<unsigned, unsigned>> &RemapChan) const {
181 Register Reg = RSI->Instr->getOperand(0).getReg();
182 MachineBasicBlock::iterator Pos = RSI->Instr;
183 MachineBasicBlock &MBB = *Pos->getParent();
184 DebugLoc DL = Pos->getDebugLoc();
185
186 Register SrcVec = BaseRSI->Instr->getOperand(0).getReg();
187 DenseMap<Register, unsigned> UpdatedRegToChan = BaseRSI->RegToChan;
188 std::vector<Register> UpdatedUndef = BaseRSI->UndefReg;
189 for (const auto &It : RSI->RegToChan) {
190 Register DstReg = MRI->createVirtualRegister(&R600::R600_Reg128RegClass);
191 unsigned SubReg = It.first;
192 unsigned Swizzle = It.second;
193 unsigned Chan = getReassignedChan(RemapChan, Swizzle);
194
195 MachineInstr *Tmp = BuildMI(MBB, Pos, DL, TII->get(R600::INSERT_SUBREG),
196 DstReg)
197 .addReg(SrcVec)
198 .addReg(SubReg)
199 .addImm(Chan);
200 UpdatedRegToChan[SubReg] = Chan;
201 std::vector<Register>::iterator ChanPos = llvm::find(UpdatedUndef, Chan);
202 if (ChanPos != UpdatedUndef.end())
203 UpdatedUndef.erase(ChanPos);
204 assert(!is_contained(UpdatedUndef, Chan) &&
205 "UpdatedUndef shouldn't contain Chan more than once!");
206 LLVM_DEBUG(dbgs() << " ->"; Tmp->dump(););
207 (void)Tmp;
208 SrcVec = DstReg;
209 }
210 MachineInstr *NewMI =
211 BuildMI(MBB, Pos, DL, TII->get(R600::COPY), Reg).addReg(SrcVec);
212 LLVM_DEBUG(dbgs() << " ->"; NewMI->dump(););
213
214 LLVM_DEBUG(dbgs() << " Updating Swizzle:\n");
215 for (MachineRegisterInfo::use_instr_iterator It = MRI->use_instr_begin(Reg),
216 E = MRI->use_instr_end(); It != E; ++It) {
217 LLVM_DEBUG(dbgs() << " "; (*It).dump(); dbgs() << " ->");
218 SwizzleInput(*It, RemapChan);
219 LLVM_DEBUG((*It).dump());
220 }
221 RSI->Instr->eraseFromParent();
222
223 // Update RSI
224 RSI->Instr = NewMI;
225 RSI->RegToChan = UpdatedRegToChan;
226 RSI->UndefReg = UpdatedUndef;
227
228 return NewMI;
229 }
230
RemoveMI(MachineInstr * MI)231 void R600VectorRegMerger::RemoveMI(MachineInstr *MI) {
232 for (auto &It : PreviousRegSeqByReg) {
233 std::vector<MachineInstr *> &MIs = It.second;
234 MIs.erase(llvm::find(MIs, MI), MIs.end());
235 }
236 for (auto &It : PreviousRegSeqByUndefCount) {
237 std::vector<MachineInstr *> &MIs = It.second;
238 MIs.erase(llvm::find(MIs, MI), MIs.end());
239 }
240 }
241
SwizzleInput(MachineInstr & MI,const std::vector<std::pair<unsigned,unsigned>> & RemapChan) const242 void R600VectorRegMerger::SwizzleInput(MachineInstr &MI,
243 const std::vector<std::pair<unsigned, unsigned>> &RemapChan) const {
244 unsigned Offset;
245 if (TII->get(MI.getOpcode()).TSFlags & R600_InstFlag::TEX_INST)
246 Offset = 2;
247 else
248 Offset = 3;
249 for (unsigned i = 0; i < 4; i++) {
250 unsigned Swizzle = MI.getOperand(i + Offset).getImm() + 1;
251 for (const auto &J : RemapChan) {
252 if (J.first == Swizzle) {
253 MI.getOperand(i + Offset).setImm(J.second - 1);
254 break;
255 }
256 }
257 }
258 }
259
areAllUsesSwizzeable(Register Reg) const260 bool R600VectorRegMerger::areAllUsesSwizzeable(Register Reg) const {
261 return llvm::all_of(MRI->use_instructions(Reg),
262 [&](const MachineInstr &MI) { return canSwizzle(MI); });
263 }
264
tryMergeUsingCommonSlot(RegSeqInfo & RSI,RegSeqInfo & CompatibleRSI,std::vector<std::pair<unsigned,unsigned>> & RemapChan)265 bool R600VectorRegMerger::tryMergeUsingCommonSlot(RegSeqInfo &RSI,
266 RegSeqInfo &CompatibleRSI,
267 std::vector<std::pair<unsigned, unsigned>> &RemapChan) {
268 for (MachineInstr::mop_iterator MOp = RSI.Instr->operands_begin(),
269 MOE = RSI.Instr->operands_end(); MOp != MOE; ++MOp) {
270 if (!MOp->isReg())
271 continue;
272 auto &Insts = PreviousRegSeqByReg[MOp->getReg()];
273 if (Insts.empty())
274 continue;
275 for (MachineInstr *MI : Insts) {
276 CompatibleRSI = PreviousRegSeq[MI];
277 if (RSI == CompatibleRSI)
278 continue;
279 if (tryMergeVector(&CompatibleRSI, &RSI, RemapChan))
280 return true;
281 }
282 }
283 return false;
284 }
285
tryMergeUsingFreeSlot(RegSeqInfo & RSI,RegSeqInfo & CompatibleRSI,std::vector<std::pair<unsigned,unsigned>> & RemapChan)286 bool R600VectorRegMerger::tryMergeUsingFreeSlot(RegSeqInfo &RSI,
287 RegSeqInfo &CompatibleRSI,
288 std::vector<std::pair<unsigned, unsigned>> &RemapChan) {
289 unsigned NeededUndefs = 4 - RSI.UndefReg.size();
290 std::vector<MachineInstr *> &MIs =
291 PreviousRegSeqByUndefCount[NeededUndefs];
292 if (MIs.empty())
293 return false;
294 CompatibleRSI = PreviousRegSeq[MIs.back()];
295 tryMergeVector(&CompatibleRSI, &RSI, RemapChan);
296 return true;
297 }
298
trackRSI(const RegSeqInfo & RSI)299 void R600VectorRegMerger::trackRSI(const RegSeqInfo &RSI) {
300 for (DenseMap<Register, unsigned>::const_iterator
301 It = RSI.RegToChan.begin(), E = RSI.RegToChan.end(); It != E; ++It) {
302 PreviousRegSeqByReg[(*It).first].push_back(RSI.Instr);
303 }
304 PreviousRegSeqByUndefCount[RSI.UndefReg.size()].push_back(RSI.Instr);
305 PreviousRegSeq[RSI.Instr] = RSI;
306 }
307
runOnMachineFunction(MachineFunction & Fn)308 bool R600VectorRegMerger::runOnMachineFunction(MachineFunction &Fn) {
309 if (skipFunction(Fn.getFunction()))
310 return false;
311
312 const R600Subtarget &ST = Fn.getSubtarget<R600Subtarget>();
313 TII = ST.getInstrInfo();
314 MRI = &Fn.getRegInfo();
315
316 for (MachineBasicBlock &MB : Fn) {
317 PreviousRegSeq.clear();
318 PreviousRegSeqByReg.clear();
319 PreviousRegSeqByUndefCount.clear();
320
321 for (MachineBasicBlock::iterator MII = MB.begin(), MIIE = MB.end();
322 MII != MIIE; ++MII) {
323 MachineInstr &MI = *MII;
324 if (MI.getOpcode() != R600::REG_SEQUENCE) {
325 if (TII->get(MI.getOpcode()).TSFlags & R600_InstFlag::TEX_INST) {
326 Register Reg = MI.getOperand(1).getReg();
327 for (MachineInstr &DefMI : MRI->def_instructions(Reg))
328 RemoveMI(&DefMI);
329 }
330 continue;
331 }
332
333 RegSeqInfo RSI(*MRI, &MI);
334
335 // All uses of MI are swizzeable ?
336 Register Reg = MI.getOperand(0).getReg();
337 if (!areAllUsesSwizzeable(Reg))
338 continue;
339
340 LLVM_DEBUG({
341 dbgs() << "Trying to optimize ";
342 MI.dump();
343 });
344
345 RegSeqInfo CandidateRSI;
346 std::vector<std::pair<unsigned, unsigned>> RemapChan;
347 LLVM_DEBUG(dbgs() << "Using common slots...\n";);
348 if (tryMergeUsingCommonSlot(RSI, CandidateRSI, RemapChan)) {
349 // Remove CandidateRSI mapping
350 RemoveMI(CandidateRSI.Instr);
351 MII = RebuildVector(&RSI, &CandidateRSI, RemapChan);
352 trackRSI(RSI);
353 continue;
354 }
355 LLVM_DEBUG(dbgs() << "Using free slots...\n";);
356 RemapChan.clear();
357 if (tryMergeUsingFreeSlot(RSI, CandidateRSI, RemapChan)) {
358 RemoveMI(CandidateRSI.Instr);
359 MII = RebuildVector(&RSI, &CandidateRSI, RemapChan);
360 trackRSI(RSI);
361 continue;
362 }
363 //Failed to merge
364 trackRSI(RSI);
365 }
366 }
367 return false;
368 }
369
createR600VectorRegMerger()370 llvm::FunctionPass *llvm::createR600VectorRegMerger() {
371 return new R600VectorRegMerger();
372 }
373