1 //===- HexagonNewValueJump.cpp - Hexagon Backend New Value Jump -----------===// 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 // This implements NewValueJump pass in Hexagon. 10 // Ideally, we should merge this as a Peephole pass prior to register 11 // allocation, but because we have a spill in between the feeder and new value 12 // jump instructions, we are forced to write after register allocation. 13 // Having said that, we should re-attempt to pull this earlier at some point 14 // in future. 15 16 // The basic approach looks for sequence of predicated jump, compare instruciton 17 // that genereates the predicate and, the feeder to the predicate. Once it finds 18 // all, it collapses compare and jump instruction into a new value jump 19 // intstructions. 20 // 21 //===----------------------------------------------------------------------===// 22 23 #include "llvm/InitializePasses.h" 24 #include "Hexagon.h" 25 #include "HexagonInstrInfo.h" 26 #include "HexagonRegisterInfo.h" 27 #include "HexagonSubtarget.h" 28 #include "llvm/ADT/Statistic.h" 29 #include "llvm/CodeGen/MachineBasicBlock.h" 30 #include "llvm/CodeGen/MachineBranchProbabilityInfo.h" 31 #include "llvm/CodeGen/MachineFunction.h" 32 #include "llvm/CodeGen/MachineFunctionPass.h" 33 #include "llvm/CodeGen/MachineInstr.h" 34 #include "llvm/CodeGen/MachineInstrBuilder.h" 35 #include "llvm/CodeGen/MachineOperand.h" 36 #include "llvm/CodeGen/MachineRegisterInfo.h" 37 #include "llvm/CodeGen/TargetOpcodes.h" 38 #include "llvm/CodeGen/TargetRegisterInfo.h" 39 #include "llvm/CodeGen/TargetSubtargetInfo.h" 40 #include "llvm/IR/DebugLoc.h" 41 #include "llvm/MC/MCInstrDesc.h" 42 #include "llvm/Pass.h" 43 #include "llvm/Support/BranchProbability.h" 44 #include "llvm/Support/CommandLine.h" 45 #include "llvm/Support/Debug.h" 46 #include "llvm/Support/ErrorHandling.h" 47 #include "llvm/Support/MathExtras.h" 48 #include "llvm/Support/raw_ostream.h" 49 #include <cassert> 50 #include <cstdint> 51 #include <iterator> 52 53 using namespace llvm; 54 55 #define DEBUG_TYPE "hexagon-nvj" 56 57 STATISTIC(NumNVJGenerated, "Number of New Value Jump Instructions created"); 58 59 static cl::opt<int> DbgNVJCount("nvj-count", cl::init(-1), cl::Hidden, 60 cl::desc("Maximum number of predicated jumps to be converted to " 61 "New Value Jump")); 62 63 static cl::opt<bool> DisableNewValueJumps("disable-nvjump", cl::Hidden, 64 cl::ZeroOrMore, cl::init(false), 65 cl::desc("Disable New Value Jumps")); 66 67 namespace llvm { 68 69 FunctionPass *createHexagonNewValueJump(); 70 void initializeHexagonNewValueJumpPass(PassRegistry&); 71 72 } // end namespace llvm 73 74 namespace { 75 76 struct HexagonNewValueJump : public MachineFunctionPass { 77 static char ID; 78 79 HexagonNewValueJump() : MachineFunctionPass(ID) {} 80 81 void getAnalysisUsage(AnalysisUsage &AU) const override { 82 AU.addRequired<MachineBranchProbabilityInfo>(); 83 MachineFunctionPass::getAnalysisUsage(AU); 84 } 85 86 StringRef getPassName() const override { return "Hexagon NewValueJump"; } 87 88 bool runOnMachineFunction(MachineFunction &Fn) override; 89 90 MachineFunctionProperties getRequiredProperties() const override { 91 return MachineFunctionProperties().set( 92 MachineFunctionProperties::Property::NoVRegs); 93 } 94 95 private: 96 const HexagonInstrInfo *QII; 97 const HexagonRegisterInfo *QRI; 98 99 /// A handle to the branch probability pass. 100 const MachineBranchProbabilityInfo *MBPI; 101 102 bool isNewValueJumpCandidate(const MachineInstr &MI) const; 103 }; 104 105 } // end anonymous namespace 106 107 char HexagonNewValueJump::ID = 0; 108 109 INITIALIZE_PASS_BEGIN(HexagonNewValueJump, "hexagon-nvj", 110 "Hexagon NewValueJump", false, false) 111 INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfo) 112 INITIALIZE_PASS_END(HexagonNewValueJump, "hexagon-nvj", 113 "Hexagon NewValueJump", false, false) 114 115 // We have identified this II could be feeder to NVJ, 116 // verify that it can be. 117 static bool canBeFeederToNewValueJump(const HexagonInstrInfo *QII, 118 const TargetRegisterInfo *TRI, 119 MachineBasicBlock::iterator II, 120 MachineBasicBlock::iterator end, 121 MachineBasicBlock::iterator skip, 122 MachineFunction &MF) { 123 // Predicated instruction can not be feeder to NVJ. 124 if (QII->isPredicated(*II)) 125 return false; 126 127 // Bail out if feederReg is a paired register (double regs in 128 // our case). One would think that we can check to see if a given 129 // register cmpReg1 or cmpReg2 is a sub register of feederReg 130 // using -- if (QRI->isSubRegister(feederReg, cmpReg1) logic 131 // before the callsite of this function 132 // But we can not as it comes in the following fashion. 133 // %d0 = Hexagon_S2_lsr_r_p killed %d0, killed %r2 134 // %r0 = KILL %r0, implicit killed %d0 135 // %p0 = CMPEQri killed %r0, 0 136 // Hence, we need to check if it's a KILL instruction. 137 if (II->getOpcode() == TargetOpcode::KILL) 138 return false; 139 140 if (II->isImplicitDef()) 141 return false; 142 143 if (QII->isSolo(*II)) 144 return false; 145 146 if (QII->isFloat(*II)) 147 return false; 148 149 // Make sure that the (unique) def operand is a register from IntRegs. 150 bool HadDef = false; 151 for (const MachineOperand &Op : II->operands()) { 152 if (!Op.isReg() || !Op.isDef()) 153 continue; 154 if (HadDef) 155 return false; 156 HadDef = true; 157 if (!Hexagon::IntRegsRegClass.contains(Op.getReg())) 158 return false; 159 } 160 assert(HadDef); 161 162 // Make sure there is no 'def' or 'use' of any of the uses of 163 // feeder insn between its definition, this MI and jump, jmpInst 164 // skipping compare, cmpInst. 165 // Here's the example. 166 // r21=memub(r22+r24<<#0) 167 // p0 = cmp.eq(r21, #0) 168 // r4=memub(r3+r21<<#0) 169 // if (p0.new) jump:t .LBB29_45 170 // Without this check, it will be converted into 171 // r4=memub(r3+r21<<#0) 172 // r21=memub(r22+r24<<#0) 173 // p0 = cmp.eq(r21, #0) 174 // if (p0.new) jump:t .LBB29_45 175 // and result WAR hazards if converted to New Value Jump. 176 for (unsigned i = 0; i < II->getNumOperands(); ++i) { 177 if (II->getOperand(i).isReg() && 178 (II->getOperand(i).isUse() || II->getOperand(i).isDef())) { 179 MachineBasicBlock::iterator localII = II; 180 ++localII; 181 Register Reg = II->getOperand(i).getReg(); 182 for (MachineBasicBlock::iterator localBegin = localII; localBegin != end; 183 ++localBegin) { 184 if (localBegin == skip) 185 continue; 186 // Check for Subregisters too. 187 if (localBegin->modifiesRegister(Reg, TRI) || 188 localBegin->readsRegister(Reg, TRI)) 189 return false; 190 } 191 } 192 } 193 return true; 194 } 195 196 // These are the common checks that need to performed 197 // to determine if 198 // 1. compare instruction can be moved before jump. 199 // 2. feeder to the compare instruction can be moved before jump. 200 static bool commonChecksToProhibitNewValueJump(bool afterRA, 201 MachineBasicBlock::iterator MII) { 202 // If store in path, bail out. 203 if (MII->mayStore()) 204 return false; 205 206 // if call in path, bail out. 207 if (MII->isCall()) 208 return false; 209 210 // if NVJ is running prior to RA, do the following checks. 211 if (!afterRA) { 212 // The following Target Opcode instructions are spurious 213 // to new value jump. If they are in the path, bail out. 214 // KILL sets kill flag on the opcode. It also sets up a 215 // single register, out of pair. 216 // %d0 = S2_lsr_r_p killed %d0, killed %r2 217 // %r0 = KILL %r0, implicit killed %d0 218 // %p0 = C2_cmpeqi killed %r0, 0 219 // PHI can be anything after RA. 220 // COPY can remateriaze things in between feeder, compare and nvj. 221 if (MII->getOpcode() == TargetOpcode::KILL || 222 MII->getOpcode() == TargetOpcode::PHI || 223 MII->getOpcode() == TargetOpcode::COPY) 224 return false; 225 226 // The following pseudo Hexagon instructions sets "use" and "def" 227 // of registers by individual passes in the backend. At this time, 228 // we don't know the scope of usage and definitions of these 229 // instructions. 230 if (MII->getOpcode() == Hexagon::LDriw_pred || 231 MII->getOpcode() == Hexagon::STriw_pred) 232 return false; 233 } 234 235 return true; 236 } 237 238 static bool canCompareBeNewValueJump(const HexagonInstrInfo *QII, 239 const TargetRegisterInfo *TRI, 240 MachineBasicBlock::iterator II, 241 unsigned pReg, 242 bool secondReg, 243 bool optLocation, 244 MachineBasicBlock::iterator end, 245 MachineFunction &MF) { 246 MachineInstr &MI = *II; 247 248 // If the second operand of the compare is an imm, make sure it's in the 249 // range specified by the arch. 250 if (!secondReg) { 251 const MachineOperand &Op2 = MI.getOperand(2); 252 if (!Op2.isImm()) 253 return false; 254 255 int64_t v = Op2.getImm(); 256 bool Valid = false; 257 258 switch (MI.getOpcode()) { 259 case Hexagon::C2_cmpeqi: 260 case Hexagon::C4_cmpneqi: 261 case Hexagon::C2_cmpgti: 262 case Hexagon::C4_cmpltei: 263 Valid = (isUInt<5>(v) || v == -1); 264 break; 265 case Hexagon::C2_cmpgtui: 266 case Hexagon::C4_cmplteui: 267 Valid = isUInt<5>(v); 268 break; 269 case Hexagon::S2_tstbit_i: 270 case Hexagon::S4_ntstbit_i: 271 Valid = (v == 0); 272 break; 273 } 274 275 if (!Valid) 276 return false; 277 } 278 279 unsigned cmpReg1, cmpOp2 = 0; // cmpOp2 assignment silences compiler warning. 280 cmpReg1 = MI.getOperand(1).getReg(); 281 282 if (secondReg) { 283 cmpOp2 = MI.getOperand(2).getReg(); 284 285 // If the same register appears as both operands, we cannot generate a new 286 // value compare. Only one operand may use the .new suffix. 287 if (cmpReg1 == cmpOp2) 288 return false; 289 290 // Make sure that the second register is not from COPY 291 // at machine code level, we don't need this, but if we decide 292 // to move new value jump prior to RA, we would be needing this. 293 MachineRegisterInfo &MRI = MF.getRegInfo(); 294 if (!Register::isPhysicalRegister(cmpOp2)) { 295 MachineInstr *def = MRI.getVRegDef(cmpOp2); 296 if (def->getOpcode() == TargetOpcode::COPY) 297 return false; 298 } 299 } 300 301 // Walk the instructions after the compare (predicate def) to the jump, 302 // and satisfy the following conditions. 303 ++II; 304 for (MachineBasicBlock::iterator localII = II; localII != end; ++localII) { 305 if (localII->isDebugInstr()) 306 continue; 307 308 // Check 1. 309 // If "common" checks fail, bail out. 310 if (!commonChecksToProhibitNewValueJump(optLocation, localII)) 311 return false; 312 313 // Check 2. 314 // If there is a def or use of predicate (result of compare), bail out. 315 if (localII->modifiesRegister(pReg, TRI) || 316 localII->readsRegister(pReg, TRI)) 317 return false; 318 319 // Check 3. 320 // If there is a def of any of the use of the compare (operands of compare), 321 // bail out. 322 // Eg. 323 // p0 = cmp.eq(r2, r0) 324 // r2 = r4 325 // if (p0.new) jump:t .LBB28_3 326 if (localII->modifiesRegister(cmpReg1, TRI) || 327 (secondReg && localII->modifiesRegister(cmpOp2, TRI))) 328 return false; 329 } 330 return true; 331 } 332 333 // Given a compare operator, return a matching New Value Jump compare operator. 334 // Make sure that MI here is included in isNewValueJumpCandidate. 335 static unsigned getNewValueJumpOpcode(MachineInstr *MI, int reg, 336 bool secondRegNewified, 337 MachineBasicBlock *jmpTarget, 338 const MachineBranchProbabilityInfo 339 *MBPI) { 340 bool taken = false; 341 MachineBasicBlock *Src = MI->getParent(); 342 const BranchProbability Prediction = 343 MBPI->getEdgeProbability(Src, jmpTarget); 344 345 if (Prediction >= BranchProbability(1,2)) 346 taken = true; 347 348 switch (MI->getOpcode()) { 349 case Hexagon::C2_cmpeq: 350 return taken ? Hexagon::J4_cmpeq_t_jumpnv_t 351 : Hexagon::J4_cmpeq_t_jumpnv_nt; 352 353 case Hexagon::C2_cmpeqi: 354 if (reg >= 0) 355 return taken ? Hexagon::J4_cmpeqi_t_jumpnv_t 356 : Hexagon::J4_cmpeqi_t_jumpnv_nt; 357 return taken ? Hexagon::J4_cmpeqn1_t_jumpnv_t 358 : Hexagon::J4_cmpeqn1_t_jumpnv_nt; 359 360 case Hexagon::C4_cmpneqi: 361 if (reg >= 0) 362 return taken ? Hexagon::J4_cmpeqi_f_jumpnv_t 363 : Hexagon::J4_cmpeqi_f_jumpnv_nt; 364 return taken ? Hexagon::J4_cmpeqn1_f_jumpnv_t : 365 Hexagon::J4_cmpeqn1_f_jumpnv_nt; 366 367 case Hexagon::C2_cmpgt: 368 if (secondRegNewified) 369 return taken ? Hexagon::J4_cmplt_t_jumpnv_t 370 : Hexagon::J4_cmplt_t_jumpnv_nt; 371 return taken ? Hexagon::J4_cmpgt_t_jumpnv_t 372 : Hexagon::J4_cmpgt_t_jumpnv_nt; 373 374 case Hexagon::C2_cmpgti: 375 if (reg >= 0) 376 return taken ? Hexagon::J4_cmpgti_t_jumpnv_t 377 : Hexagon::J4_cmpgti_t_jumpnv_nt; 378 return taken ? Hexagon::J4_cmpgtn1_t_jumpnv_t 379 : Hexagon::J4_cmpgtn1_t_jumpnv_nt; 380 381 case Hexagon::C2_cmpgtu: 382 if (secondRegNewified) 383 return taken ? Hexagon::J4_cmpltu_t_jumpnv_t 384 : Hexagon::J4_cmpltu_t_jumpnv_nt; 385 return taken ? Hexagon::J4_cmpgtu_t_jumpnv_t 386 : Hexagon::J4_cmpgtu_t_jumpnv_nt; 387 388 case Hexagon::C2_cmpgtui: 389 return taken ? Hexagon::J4_cmpgtui_t_jumpnv_t 390 : Hexagon::J4_cmpgtui_t_jumpnv_nt; 391 392 case Hexagon::C4_cmpneq: 393 return taken ? Hexagon::J4_cmpeq_f_jumpnv_t 394 : Hexagon::J4_cmpeq_f_jumpnv_nt; 395 396 case Hexagon::C4_cmplte: 397 if (secondRegNewified) 398 return taken ? Hexagon::J4_cmplt_f_jumpnv_t 399 : Hexagon::J4_cmplt_f_jumpnv_nt; 400 return taken ? Hexagon::J4_cmpgt_f_jumpnv_t 401 : Hexagon::J4_cmpgt_f_jumpnv_nt; 402 403 case Hexagon::C4_cmplteu: 404 if (secondRegNewified) 405 return taken ? Hexagon::J4_cmpltu_f_jumpnv_t 406 : Hexagon::J4_cmpltu_f_jumpnv_nt; 407 return taken ? Hexagon::J4_cmpgtu_f_jumpnv_t 408 : Hexagon::J4_cmpgtu_f_jumpnv_nt; 409 410 case Hexagon::C4_cmpltei: 411 if (reg >= 0) 412 return taken ? Hexagon::J4_cmpgti_f_jumpnv_t 413 : Hexagon::J4_cmpgti_f_jumpnv_nt; 414 return taken ? Hexagon::J4_cmpgtn1_f_jumpnv_t 415 : Hexagon::J4_cmpgtn1_f_jumpnv_nt; 416 417 case Hexagon::C4_cmplteui: 418 return taken ? Hexagon::J4_cmpgtui_f_jumpnv_t 419 : Hexagon::J4_cmpgtui_f_jumpnv_nt; 420 421 default: 422 llvm_unreachable("Could not find matching New Value Jump instruction."); 423 } 424 // return *some value* to avoid compiler warning 425 return 0; 426 } 427 428 bool HexagonNewValueJump::isNewValueJumpCandidate( 429 const MachineInstr &MI) const { 430 switch (MI.getOpcode()) { 431 case Hexagon::C2_cmpeq: 432 case Hexagon::C2_cmpeqi: 433 case Hexagon::C2_cmpgt: 434 case Hexagon::C2_cmpgti: 435 case Hexagon::C2_cmpgtu: 436 case Hexagon::C2_cmpgtui: 437 case Hexagon::C4_cmpneq: 438 case Hexagon::C4_cmpneqi: 439 case Hexagon::C4_cmplte: 440 case Hexagon::C4_cmplteu: 441 case Hexagon::C4_cmpltei: 442 case Hexagon::C4_cmplteui: 443 return true; 444 445 default: 446 return false; 447 } 448 } 449 450 bool HexagonNewValueJump::runOnMachineFunction(MachineFunction &MF) { 451 LLVM_DEBUG(dbgs() << "********** Hexagon New Value Jump **********\n" 452 << "********** Function: " << MF.getName() << "\n"); 453 454 if (skipFunction(MF.getFunction())) 455 return false; 456 457 // If we move NewValueJump before register allocation we'll need live variable 458 // analysis here too. 459 460 QII = static_cast<const HexagonInstrInfo *>(MF.getSubtarget().getInstrInfo()); 461 QRI = static_cast<const HexagonRegisterInfo *>( 462 MF.getSubtarget().getRegisterInfo()); 463 MBPI = &getAnalysis<MachineBranchProbabilityInfo>(); 464 465 if (DisableNewValueJumps || 466 !MF.getSubtarget<HexagonSubtarget>().useNewValueJumps()) 467 return false; 468 469 int nvjCount = DbgNVJCount; 470 int nvjGenerated = 0; 471 472 // Loop through all the bb's of the function 473 for (MachineFunction::iterator MBBb = MF.begin(), MBBe = MF.end(); 474 MBBb != MBBe; ++MBBb) { 475 MachineBasicBlock *MBB = &*MBBb; 476 477 LLVM_DEBUG(dbgs() << "** dumping bb ** " << MBB->getNumber() << "\n"); 478 LLVM_DEBUG(MBB->dump()); 479 LLVM_DEBUG(dbgs() << "\n" 480 << "********** dumping instr bottom up **********\n"); 481 bool foundJump = false; 482 bool foundCompare = false; 483 bool invertPredicate = false; 484 unsigned predReg = 0; // predicate reg of the jump. 485 unsigned cmpReg1 = 0; 486 int cmpOp2 = 0; 487 MachineBasicBlock::iterator jmpPos; 488 MachineBasicBlock::iterator cmpPos; 489 MachineInstr *cmpInstr = nullptr, *jmpInstr = nullptr; 490 MachineBasicBlock *jmpTarget = nullptr; 491 bool afterRA = false; 492 bool isSecondOpReg = false; 493 bool isSecondOpNewified = false; 494 // Traverse the basic block - bottom up 495 for (MachineBasicBlock::iterator MII = MBB->end(), E = MBB->begin(); 496 MII != E;) { 497 MachineInstr &MI = *--MII; 498 if (MI.isDebugInstr()) { 499 continue; 500 } 501 502 if ((nvjCount == 0) || (nvjCount > -1 && nvjCount <= nvjGenerated)) 503 break; 504 505 LLVM_DEBUG(dbgs() << "Instr: "; MI.dump(); dbgs() << "\n"); 506 507 if (!foundJump && (MI.getOpcode() == Hexagon::J2_jumpt || 508 MI.getOpcode() == Hexagon::J2_jumptpt || 509 MI.getOpcode() == Hexagon::J2_jumpf || 510 MI.getOpcode() == Hexagon::J2_jumpfpt || 511 MI.getOpcode() == Hexagon::J2_jumptnewpt || 512 MI.getOpcode() == Hexagon::J2_jumptnew || 513 MI.getOpcode() == Hexagon::J2_jumpfnewpt || 514 MI.getOpcode() == Hexagon::J2_jumpfnew)) { 515 // This is where you would insert your compare and 516 // instr that feeds compare 517 jmpPos = MII; 518 jmpInstr = &MI; 519 predReg = MI.getOperand(0).getReg(); 520 afterRA = Register::isPhysicalRegister(predReg); 521 522 // If ifconverter had not messed up with the kill flags of the 523 // operands, the following check on the kill flag would suffice. 524 // if(!jmpInstr->getOperand(0).isKill()) break; 525 526 // This predicate register is live out of BB 527 // this would only work if we can actually use Live 528 // variable analysis on phy regs - but LLVM does not 529 // provide LV analysis on phys regs. 530 //if(LVs.isLiveOut(predReg, *MBB)) break; 531 532 // Get all the successors of this block - which will always 533 // be 2. Check if the predicate register is live-in in those 534 // successor. If yes, we can not delete the predicate - 535 // I am doing this only because LLVM does not provide LiveOut 536 // at the BB level. 537 bool predLive = false; 538 for (MachineBasicBlock::const_succ_iterator SI = MBB->succ_begin(), 539 SIE = MBB->succ_end(); 540 SI != SIE; ++SI) { 541 MachineBasicBlock *succMBB = *SI; 542 if (succMBB->isLiveIn(predReg)) 543 predLive = true; 544 } 545 if (predLive) 546 break; 547 548 if (!MI.getOperand(1).isMBB()) 549 continue; 550 jmpTarget = MI.getOperand(1).getMBB(); 551 foundJump = true; 552 if (MI.getOpcode() == Hexagon::J2_jumpf || 553 MI.getOpcode() == Hexagon::J2_jumpfnewpt || 554 MI.getOpcode() == Hexagon::J2_jumpfnew) { 555 invertPredicate = true; 556 } 557 continue; 558 } 559 560 // No new value jump if there is a barrier. A barrier has to be in its 561 // own packet. A barrier has zero operands. We conservatively bail out 562 // here if we see any instruction with zero operands. 563 if (foundJump && MI.getNumOperands() == 0) 564 break; 565 566 if (foundJump && !foundCompare && MI.getOperand(0).isReg() && 567 MI.getOperand(0).getReg() == predReg) { 568 // Not all compares can be new value compare. Arch Spec: 7.6.1.1 569 if (isNewValueJumpCandidate(MI)) { 570 assert( 571 (MI.getDesc().isCompare()) && 572 "Only compare instruction can be collapsed into New Value Jump"); 573 isSecondOpReg = MI.getOperand(2).isReg(); 574 575 if (!canCompareBeNewValueJump(QII, QRI, MII, predReg, isSecondOpReg, 576 afterRA, jmpPos, MF)) 577 break; 578 579 cmpInstr = &MI; 580 cmpPos = MII; 581 foundCompare = true; 582 583 // We need cmpReg1 and cmpOp2(imm or reg) while building 584 // new value jump instruction. 585 cmpReg1 = MI.getOperand(1).getReg(); 586 587 if (isSecondOpReg) 588 cmpOp2 = MI.getOperand(2).getReg(); 589 else 590 cmpOp2 = MI.getOperand(2).getImm(); 591 continue; 592 } 593 } 594 595 if (foundCompare && foundJump) { 596 // If "common" checks fail, bail out on this BB. 597 if (!commonChecksToProhibitNewValueJump(afterRA, MII)) 598 break; 599 600 bool foundFeeder = false; 601 MachineBasicBlock::iterator feederPos = MII; 602 if (MI.getOperand(0).isReg() && MI.getOperand(0).isDef() && 603 (MI.getOperand(0).getReg() == cmpReg1 || 604 (isSecondOpReg && 605 MI.getOperand(0).getReg() == (unsigned)cmpOp2))) { 606 607 Register feederReg = MI.getOperand(0).getReg(); 608 609 // First try to see if we can get the feeder from the first operand 610 // of the compare. If we can not, and if secondOpReg is true 611 // (second operand of the compare is also register), try that one. 612 // TODO: Try to come up with some heuristic to figure out which 613 // feeder would benefit. 614 615 if (feederReg == cmpReg1) { 616 if (!canBeFeederToNewValueJump(QII, QRI, MII, jmpPos, cmpPos, MF)) { 617 if (!isSecondOpReg) 618 break; 619 else 620 continue; 621 } else 622 foundFeeder = true; 623 } 624 625 if (!foundFeeder && isSecondOpReg && feederReg == (unsigned)cmpOp2) 626 if (!canBeFeederToNewValueJump(QII, QRI, MII, jmpPos, cmpPos, MF)) 627 break; 628 629 if (isSecondOpReg) { 630 // In case of CMPLT, or CMPLTU, or EQ with the second register 631 // to newify, swap the operands. 632 unsigned COp = cmpInstr->getOpcode(); 633 if ((COp == Hexagon::C2_cmpeq || COp == Hexagon::C4_cmpneq) && 634 (feederReg == (unsigned)cmpOp2)) { 635 unsigned tmp = cmpReg1; 636 cmpReg1 = cmpOp2; 637 cmpOp2 = tmp; 638 } 639 640 // Now we have swapped the operands, all we need to check is, 641 // if the second operand (after swap) is the feeder. 642 // And if it is, make a note. 643 if (feederReg == (unsigned)cmpOp2) 644 isSecondOpNewified = true; 645 } 646 647 // Now that we are moving feeder close the jump, 648 // make sure we are respecting the kill values of 649 // the operands of the feeder. 650 651 auto TransferKills = [jmpPos,cmpPos] (MachineInstr &MI) { 652 for (MachineOperand &MO : MI.operands()) { 653 if (!MO.isReg() || !MO.isUse()) 654 continue; 655 Register UseR = MO.getReg(); 656 for (auto I = std::next(MI.getIterator()); I != jmpPos; ++I) { 657 if (I == cmpPos) 658 continue; 659 for (MachineOperand &Op : I->operands()) { 660 if (!Op.isReg() || !Op.isUse() || !Op.isKill()) 661 continue; 662 if (Op.getReg() != UseR) 663 continue; 664 // We found that there is kill of a use register 665 // Set up a kill flag on the register 666 Op.setIsKill(false); 667 MO.setIsKill(true); 668 return; 669 } 670 } 671 } 672 }; 673 674 TransferKills(*feederPos); 675 TransferKills(*cmpPos); 676 bool MO1IsKill = cmpPos->killsRegister(cmpReg1, QRI); 677 bool MO2IsKill = isSecondOpReg && cmpPos->killsRegister(cmpOp2, QRI); 678 679 MBB->splice(jmpPos, MI.getParent(), MI); 680 MBB->splice(jmpPos, MI.getParent(), cmpInstr); 681 DebugLoc dl = MI.getDebugLoc(); 682 MachineInstr *NewMI; 683 684 assert((isNewValueJumpCandidate(*cmpInstr)) && 685 "This compare is not a New Value Jump candidate."); 686 unsigned opc = getNewValueJumpOpcode(cmpInstr, cmpOp2, 687 isSecondOpNewified, 688 jmpTarget, MBPI); 689 if (invertPredicate) 690 opc = QII->getInvertedPredicatedOpcode(opc); 691 692 if (isSecondOpReg) 693 NewMI = BuildMI(*MBB, jmpPos, dl, QII->get(opc)) 694 .addReg(cmpReg1, getKillRegState(MO1IsKill)) 695 .addReg(cmpOp2, getKillRegState(MO2IsKill)) 696 .addMBB(jmpTarget); 697 698 else 699 NewMI = BuildMI(*MBB, jmpPos, dl, QII->get(opc)) 700 .addReg(cmpReg1, getKillRegState(MO1IsKill)) 701 .addImm(cmpOp2) 702 .addMBB(jmpTarget); 703 704 assert(NewMI && "New Value Jump Instruction Not created!"); 705 (void)NewMI; 706 if (cmpInstr->getOperand(0).isReg() && 707 cmpInstr->getOperand(0).isKill()) 708 cmpInstr->getOperand(0).setIsKill(false); 709 if (cmpInstr->getOperand(1).isReg() && 710 cmpInstr->getOperand(1).isKill()) 711 cmpInstr->getOperand(1).setIsKill(false); 712 cmpInstr->eraseFromParent(); 713 jmpInstr->eraseFromParent(); 714 ++nvjGenerated; 715 ++NumNVJGenerated; 716 break; 717 } 718 } 719 } 720 } 721 722 return true; 723 } 724 725 FunctionPass *llvm::createHexagonNewValueJump() { 726 return new HexagonNewValueJump(); 727 } 728
Indexes created Mon Aug 10 00:24:53 UTC 2026