xref: /freebsd/contrib/llvm-project/llvm/lib/Target/Hexagon/HexagonGenPredicate.cpp (revision 9f23cbd6cae82fd77edfad7173432fa8dccd0a95) 
1 //===- HexagonGenPredicate.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 #include "HexagonInstrInfo.h"
10 #include "HexagonSubtarget.h"
11 #include "llvm/ADT/SetVector.h"
12 #include "llvm/ADT/StringRef.h"
13 #include "llvm/CodeGen/MachineBasicBlock.h"
14 #include "llvm/CodeGen/MachineDominators.h"
15 #include "llvm/CodeGen/MachineFunction.h"
16 #include "llvm/CodeGen/MachineFunctionPass.h"
17 #include "llvm/CodeGen/MachineInstr.h"
18 #include "llvm/CodeGen/MachineInstrBuilder.h"
19 #include "llvm/CodeGen/MachineOperand.h"
20 #include "llvm/CodeGen/MachineRegisterInfo.h"
21 #include "llvm/CodeGen/TargetRegisterInfo.h"
22 #include "llvm/IR/DebugLoc.h"
23 #include "llvm/InitializePasses.h"
24 #include "llvm/Pass.h"
25 #include "llvm/Support/Compiler.h"
26 #include "llvm/Support/Debug.h"
27 #include "llvm/Support/ErrorHandling.h"
28 #include "llvm/Support/raw_ostream.h"
29 #include <cassert>
30 #include <iterator>
31 #include <map>
32 #include <queue>
33 #include <set>
34 #include <utility>
35 
36 #define DEBUG_TYPE "gen-pred"
37 
38 using namespace llvm;
39 
40 namespace llvm {
41 
42   void initializeHexagonGenPredicatePass(PassRegistry& Registry);
43   FunctionPass *createHexagonGenPredicate();
44 
45 } // end namespace llvm
46 
47 namespace {
48 
49   // FIXME: Use TargetInstrInfo::RegSubRegPair
50   struct RegisterSubReg {
51     Register R;
52     unsigned S;
53 
54     RegisterSubReg(unsigned r = 0, unsigned s = 0) : R(r), S(s) {}
55     RegisterSubReg(const MachineOperand &MO) : R(MO.getReg()), S(MO.getSubReg()) {}
56     RegisterSubReg(const Register &Reg) : R(Reg), S(0) {}
57 
58     bool operator== (const RegisterSubReg &Reg) const {
59       return R == Reg.R && S == Reg.S;
60     }
61 
62     bool operator< (const RegisterSubReg &Reg) const {
63       return R < Reg.R || (R == Reg.R && S < Reg.S);
64     }
65   };
66 
67   struct PrintRegister {
68     friend raw_ostream &operator<< (raw_ostream &OS, const PrintRegister &PR);
69 
70     PrintRegister(RegisterSubReg R, const TargetRegisterInfo &I) : Reg(R), TRI(I) {}
71 
72   private:
73     RegisterSubReg Reg;
74     const TargetRegisterInfo &TRI;
75   };
76 
77   raw_ostream &operator<< (raw_ostream &OS, const PrintRegister &PR)
78     LLVM_ATTRIBUTE_UNUSED;
79   raw_ostream &operator<< (raw_ostream &OS, const PrintRegister &PR) {
80     return OS << printReg(PR.Reg.R, &PR.TRI, PR.Reg.S);
81   }
82 
83   class HexagonGenPredicate : public MachineFunctionPass {
84   public:
85     static char ID;
86 
87     HexagonGenPredicate() : MachineFunctionPass(ID) {
88       initializeHexagonGenPredicatePass(*PassRegistry::getPassRegistry());
89     }
90 
91     StringRef getPassName() const override {
92       return "Hexagon generate predicate operations";
93     }
94 
95     void getAnalysisUsage(AnalysisUsage &AU) const override {
96       AU.addRequired<MachineDominatorTree>();
97       AU.addPreserved<MachineDominatorTree>();
98       MachineFunctionPass::getAnalysisUsage(AU);
99     }
100 
101     bool runOnMachineFunction(MachineFunction &MF) override;
102 
103   private:
104     using VectOfInst = SetVector<MachineInstr *>;
105     using SetOfReg = std::set<RegisterSubReg>;
106     using RegToRegMap = std::map<RegisterSubReg, RegisterSubReg>;
107 
108     const HexagonInstrInfo *TII = nullptr;
109     const HexagonRegisterInfo *TRI = nullptr;
110     MachineRegisterInfo *MRI = nullptr;
111     SetOfReg PredGPRs;
112     VectOfInst PUsers;
113     RegToRegMap G2P;
114 
115     bool isPredReg(Register R);
116     void collectPredicateGPR(MachineFunction &MF);
117     void processPredicateGPR(const RegisterSubReg &Reg);
118     unsigned getPredForm(unsigned Opc);
119     bool isConvertibleToPredForm(const MachineInstr *MI);
120     bool isScalarCmp(unsigned Opc);
121     bool isScalarPred(RegisterSubReg PredReg);
122     RegisterSubReg getPredRegFor(const RegisterSubReg &Reg);
123     bool convertToPredForm(MachineInstr *MI);
124     bool eliminatePredCopies(MachineFunction &MF);
125   };
126 
127 } // end anonymous namespace
128 
129 char HexagonGenPredicate::ID = 0;
130 
131 INITIALIZE_PASS_BEGIN(HexagonGenPredicate, "hexagon-gen-pred",
132   "Hexagon generate predicate operations", false, false)
133 INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
134 INITIALIZE_PASS_END(HexagonGenPredicate, "hexagon-gen-pred",
135   "Hexagon generate predicate operations", false, false)
136 
137 bool HexagonGenPredicate::isPredReg(Register R) {
138   if (!R.isVirtual())
139     return false;
140   const TargetRegisterClass *RC = MRI->getRegClass(R);
141   return RC == &Hexagon::PredRegsRegClass;
142 }
143 
144 unsigned HexagonGenPredicate::getPredForm(unsigned Opc) {
145   using namespace Hexagon;
146 
147   switch (Opc) {
148     case A2_and:
149     case A2_andp:
150       return C2_and;
151     case A4_andn:
152     case A4_andnp:
153       return C2_andn;
154     case M4_and_and:
155       return C4_and_and;
156     case M4_and_andn:
157       return C4_and_andn;
158     case M4_and_or:
159       return C4_and_or;
160 
161     case A2_or:
162     case A2_orp:
163       return C2_or;
164     case A4_orn:
165     case A4_ornp:
166       return C2_orn;
167     case M4_or_and:
168       return C4_or_and;
169     case M4_or_andn:
170       return C4_or_andn;
171     case M4_or_or:
172       return C4_or_or;
173 
174     case A2_xor:
175     case A2_xorp:
176       return C2_xor;
177 
178     case C2_tfrrp:
179       return COPY;
180   }
181   // The opcode corresponding to 0 is TargetOpcode::PHI. We can use 0 here
182   // to denote "none", but we need to make sure that none of the valid opcodes
183   // that we return will ever be 0.
184   static_assert(PHI == 0, "Use different value for <none>");
185   return 0;
186 }
187 
188 bool HexagonGenPredicate::isConvertibleToPredForm(const MachineInstr *MI) {
189   unsigned Opc = MI->getOpcode();
190   if (getPredForm(Opc) != 0)
191     return true;
192 
193   // Comparisons against 0 are also convertible. This does not apply to
194   // A4_rcmpeqi or A4_rcmpneqi, since they produce values 0 or 1, which
195   // may not match the value that the predicate register would have if
196   // it was converted to a predicate form.
197   switch (Opc) {
198     case Hexagon::C2_cmpeqi:
199     case Hexagon::C4_cmpneqi:
200       if (MI->getOperand(2).isImm() && MI->getOperand(2).getImm() == 0)
201         return true;
202       break;
203   }
204   return false;
205 }
206 
207 void HexagonGenPredicate::collectPredicateGPR(MachineFunction &MF) {
208   for (MachineBasicBlock &B : MF) {
209     for (MachineInstr &MI : B) {
210       unsigned Opc = MI.getOpcode();
211       switch (Opc) {
212         case Hexagon::C2_tfrpr:
213         case TargetOpcode::COPY:
214           if (isPredReg(MI.getOperand(1).getReg())) {
215             RegisterSubReg RD = MI.getOperand(0);
216             if (RD.R.isVirtual())
217               PredGPRs.insert(RD);
218           }
219           break;
220       }
221     }
222   }
223 }
224 
225 void HexagonGenPredicate::processPredicateGPR(const RegisterSubReg &Reg) {
226   LLVM_DEBUG(dbgs() << __func__ << ": " << printReg(Reg.R, TRI, Reg.S) << "\n");
227   using use_iterator = MachineRegisterInfo::use_iterator;
228 
229   use_iterator I = MRI->use_begin(Reg.R), E = MRI->use_end();
230   if (I == E) {
231     LLVM_DEBUG(dbgs() << "Dead reg: " << printReg(Reg.R, TRI, Reg.S) << '\n');
232     MachineInstr *DefI = MRI->getVRegDef(Reg.R);
233     DefI->eraseFromParent();
234     return;
235   }
236 
237   for (; I != E; ++I) {
238     MachineInstr *UseI = I->getParent();
239     if (isConvertibleToPredForm(UseI))
240       PUsers.insert(UseI);
241   }
242 }
243 
244 RegisterSubReg HexagonGenPredicate::getPredRegFor(const RegisterSubReg &Reg) {
245   // Create a predicate register for a given Reg. The newly created register
246   // will have its value copied from Reg, so that it can be later used as
247   // an operand in other instructions.
248   assert(Reg.R.isVirtual());
249   RegToRegMap::iterator F = G2P.find(Reg);
250   if (F != G2P.end())
251     return F->second;
252 
253   LLVM_DEBUG(dbgs() << __func__ << ": " << PrintRegister(Reg, *TRI));
254   MachineInstr *DefI = MRI->getVRegDef(Reg.R);
255   assert(DefI);
256   unsigned Opc = DefI->getOpcode();
257   if (Opc == Hexagon::C2_tfrpr || Opc == TargetOpcode::COPY) {
258     assert(DefI->getOperand(0).isDef() && DefI->getOperand(1).isUse());
259     RegisterSubReg PR = DefI->getOperand(1);
260     G2P.insert(std::make_pair(Reg, PR));
261     LLVM_DEBUG(dbgs() << " -> " << PrintRegister(PR, *TRI) << '\n');
262     return PR;
263   }
264 
265   MachineBasicBlock &B = *DefI->getParent();
266   DebugLoc DL = DefI->getDebugLoc();
267   const TargetRegisterClass *PredRC = &Hexagon::PredRegsRegClass;
268   Register NewPR = MRI->createVirtualRegister(PredRC);
269 
270   // For convertible instructions, do not modify them, so that they can
271   // be converted later.  Generate a copy from Reg to NewPR.
272   if (isConvertibleToPredForm(DefI)) {
273     MachineBasicBlock::iterator DefIt = DefI;
274     BuildMI(B, std::next(DefIt), DL, TII->get(TargetOpcode::COPY), NewPR)
275       .addReg(Reg.R, 0, Reg.S);
276     G2P.insert(std::make_pair(Reg, RegisterSubReg(NewPR)));
277     LLVM_DEBUG(dbgs() << " -> !" << PrintRegister(RegisterSubReg(NewPR), *TRI)
278                       << '\n');
279     return RegisterSubReg(NewPR);
280   }
281 
282   llvm_unreachable("Invalid argument");
283 }
284 
285 bool HexagonGenPredicate::isScalarCmp(unsigned Opc) {
286   switch (Opc) {
287     case Hexagon::C2_cmpeq:
288     case Hexagon::C2_cmpgt:
289     case Hexagon::C2_cmpgtu:
290     case Hexagon::C2_cmpeqp:
291     case Hexagon::C2_cmpgtp:
292     case Hexagon::C2_cmpgtup:
293     case Hexagon::C2_cmpeqi:
294     case Hexagon::C2_cmpgti:
295     case Hexagon::C2_cmpgtui:
296     case Hexagon::C2_cmpgei:
297     case Hexagon::C2_cmpgeui:
298     case Hexagon::C4_cmpneqi:
299     case Hexagon::C4_cmpltei:
300     case Hexagon::C4_cmplteui:
301     case Hexagon::C4_cmpneq:
302     case Hexagon::C4_cmplte:
303     case Hexagon::C4_cmplteu:
304     case Hexagon::A4_cmpbeq:
305     case Hexagon::A4_cmpbeqi:
306     case Hexagon::A4_cmpbgtu:
307     case Hexagon::A4_cmpbgtui:
308     case Hexagon::A4_cmpbgt:
309     case Hexagon::A4_cmpbgti:
310     case Hexagon::A4_cmpheq:
311     case Hexagon::A4_cmphgt:
312     case Hexagon::A4_cmphgtu:
313     case Hexagon::A4_cmpheqi:
314     case Hexagon::A4_cmphgti:
315     case Hexagon::A4_cmphgtui:
316       return true;
317   }
318   return false;
319 }
320 
321 bool HexagonGenPredicate::isScalarPred(RegisterSubReg PredReg) {
322   std::queue<RegisterSubReg> WorkQ;
323   WorkQ.push(PredReg);
324 
325   while (!WorkQ.empty()) {
326     RegisterSubReg PR = WorkQ.front();
327     WorkQ.pop();
328     const MachineInstr *DefI = MRI->getVRegDef(PR.R);
329     if (!DefI)
330       return false;
331     unsigned DefOpc = DefI->getOpcode();
332     switch (DefOpc) {
333       case TargetOpcode::COPY: {
334         const TargetRegisterClass *PredRC = &Hexagon::PredRegsRegClass;
335         if (MRI->getRegClass(PR.R) != PredRC)
336           return false;
337         // If it is a copy between two predicate registers, fall through.
338         [[fallthrough]];
339       }
340       case Hexagon::C2_and:
341       case Hexagon::C2_andn:
342       case Hexagon::C4_and_and:
343       case Hexagon::C4_and_andn:
344       case Hexagon::C4_and_or:
345       case Hexagon::C2_or:
346       case Hexagon::C2_orn:
347       case Hexagon::C4_or_and:
348       case Hexagon::C4_or_andn:
349       case Hexagon::C4_or_or:
350       case Hexagon::C4_or_orn:
351       case Hexagon::C2_xor:
352         // Add operands to the queue.
353         for (const MachineOperand &MO : DefI->operands())
354           if (MO.isReg() && MO.isUse())
355             WorkQ.push(RegisterSubReg(MO.getReg()));
356         break;
357 
358       // All non-vector compares are ok, everything else is bad.
359       default:
360         return isScalarCmp(DefOpc);
361     }
362   }
363 
364   return true;
365 }
366 
367 bool HexagonGenPredicate::convertToPredForm(MachineInstr *MI) {
368   LLVM_DEBUG(dbgs() << __func__ << ": " << MI << " " << *MI);
369 
370   unsigned Opc = MI->getOpcode();
371   assert(isConvertibleToPredForm(MI));
372   unsigned NumOps = MI->getNumOperands();
373   for (unsigned i = 0; i < NumOps; ++i) {
374     MachineOperand &MO = MI->getOperand(i);
375     if (!MO.isReg() || !MO.isUse())
376       continue;
377     RegisterSubReg Reg(MO);
378     if (Reg.S && Reg.S != Hexagon::isub_lo)
379       return false;
380     if (!PredGPRs.count(Reg))
381       return false;
382   }
383 
384   MachineBasicBlock &B = *MI->getParent();
385   DebugLoc DL = MI->getDebugLoc();
386 
387   unsigned NewOpc = getPredForm(Opc);
388   // Special case for comparisons against 0.
389   if (NewOpc == 0) {
390     switch (Opc) {
391       case Hexagon::C2_cmpeqi:
392         NewOpc = Hexagon::C2_not;
393         break;
394       case Hexagon::C4_cmpneqi:
395         NewOpc = TargetOpcode::COPY;
396         break;
397       default:
398         return false;
399     }
400 
401     // If it's a scalar predicate register, then all bits in it are
402     // the same. Otherwise, to determine whether all bits are 0 or not
403     // we would need to use any8.
404     RegisterSubReg PR = getPredRegFor(MI->getOperand(1));
405     if (!isScalarPred(PR))
406       return false;
407     // This will skip the immediate argument when creating the predicate
408     // version instruction.
409     NumOps = 2;
410   }
411 
412   // Check that def is in operand #0.
413   MachineOperand &Op0 = MI->getOperand(0);
414   assert(Op0.isDef());
415   RegisterSubReg OutR(Op0);
416 
417   // Don't use getPredRegFor, since it will create an association between
418   // the argument and a created predicate register (i.e. it will insert a
419   // copy if a new predicate register is created).
420   const TargetRegisterClass *PredRC = &Hexagon::PredRegsRegClass;
421   RegisterSubReg NewPR = MRI->createVirtualRegister(PredRC);
422   MachineInstrBuilder MIB = BuildMI(B, MI, DL, TII->get(NewOpc), NewPR.R);
423 
424   // Add predicate counterparts of the GPRs.
425   for (unsigned i = 1; i < NumOps; ++i) {
426     RegisterSubReg GPR = MI->getOperand(i);
427     RegisterSubReg Pred = getPredRegFor(GPR);
428     MIB.addReg(Pred.R, 0, Pred.S);
429   }
430   LLVM_DEBUG(dbgs() << "generated: " << *MIB);
431 
432   // Generate a copy-out: NewGPR = NewPR, and replace all uses of OutR
433   // with NewGPR.
434   const TargetRegisterClass *RC = MRI->getRegClass(OutR.R);
435   Register NewOutR = MRI->createVirtualRegister(RC);
436   BuildMI(B, MI, DL, TII->get(TargetOpcode::COPY), NewOutR)
437     .addReg(NewPR.R, 0, NewPR.S);
438   MRI->replaceRegWith(OutR.R, NewOutR);
439   MI->eraseFromParent();
440 
441   // If the processed instruction was C2_tfrrp (i.e. Rn = Pm; Pk = Rn),
442   // then the output will be a predicate register.  Do not visit the
443   // users of it.
444   if (!isPredReg(NewOutR)) {
445     RegisterSubReg R(NewOutR);
446     PredGPRs.insert(R);
447     processPredicateGPR(R);
448   }
449   return true;
450 }
451 
452 bool HexagonGenPredicate::eliminatePredCopies(MachineFunction &MF) {
453   LLVM_DEBUG(dbgs() << __func__ << "\n");
454   const TargetRegisterClass *PredRC = &Hexagon::PredRegsRegClass;
455   bool Changed = false;
456   VectOfInst Erase;
457 
458   // First, replace copies
459   //   IntR = PredR1
460   //   PredR2 = IntR
461   // with
462   //   PredR2 = PredR1
463   // Such sequences can be generated when a copy-into-pred is generated from
464   // a gpr register holding a result of a convertible instruction. After
465   // the convertible instruction is converted, its predicate result will be
466   // copied back into the original gpr.
467 
468   for (MachineBasicBlock &MBB : MF) {
469     for (MachineInstr &MI : MBB) {
470       if (MI.getOpcode() != TargetOpcode::COPY)
471         continue;
472       RegisterSubReg DR = MI.getOperand(0);
473       RegisterSubReg SR = MI.getOperand(1);
474       if (!DR.R.isVirtual())
475         continue;
476       if (!SR.R.isVirtual())
477         continue;
478       if (MRI->getRegClass(DR.R) != PredRC)
479         continue;
480       if (MRI->getRegClass(SR.R) != PredRC)
481         continue;
482       assert(!DR.S && !SR.S && "Unexpected subregister");
483       MRI->replaceRegWith(DR.R, SR.R);
484       Erase.insert(&MI);
485       Changed = true;
486     }
487   }
488 
489   for (MachineInstr *MI : Erase)
490     MI->eraseFromParent();
491 
492   return Changed;
493 }
494 
495 bool HexagonGenPredicate::runOnMachineFunction(MachineFunction &MF) {
496   if (skipFunction(MF.getFunction()))
497     return false;
498 
499   TII = MF.getSubtarget<HexagonSubtarget>().getInstrInfo();
500   TRI = MF.getSubtarget<HexagonSubtarget>().getRegisterInfo();
501   MRI = &MF.getRegInfo();
502   PredGPRs.clear();
503   PUsers.clear();
504   G2P.clear();
505 
506   bool Changed = false;
507   collectPredicateGPR(MF);
508   for (const RegisterSubReg &R : PredGPRs)
509     processPredicateGPR(R);
510 
511   bool Again;
512   do {
513     Again = false;
514     VectOfInst Processed, Copy;
515 
516     Copy = PUsers;
517     for (MachineInstr *MI : Copy) {
518       bool Done = convertToPredForm(MI);
519       if (Done) {
520         Processed.insert(MI);
521         Again = true;
522       }
523     }
524     Changed |= Again;
525 
526     auto Done = [Processed] (MachineInstr *MI) -> bool {
527       return Processed.count(MI);
528     };
529     PUsers.remove_if(Done);
530   } while (Again);
531 
532   Changed |= eliminatePredCopies(MF);
533   return Changed;
534 }
535 
536 FunctionPass *llvm::createHexagonGenPredicate() {
537   return new HexagonGenPredicate();
538 }
539