lib/Target/PowerPC/PPCTargetTransformInfo.cpp

   1 //===-- PPCTargetTransformInfo.cpp - PPC specific TTI ---------------------===//
   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 "PPCTargetTransformInfo.h"
  10 #include "llvm/Analysis/TargetTransformInfo.h"
  11 #include "llvm/CodeGen/BasicTTIImpl.h"
  12 #include "llvm/CodeGen/CostTable.h"
  13 #include "llvm/CodeGen/TargetLowering.h"
  14 #include "llvm/Support/CommandLine.h"
  15 #include "llvm/Support/Debug.h"
  16 using namespace llvm;
  17
  18 #define DEBUG_TYPE "ppctti"
  19
  20 static cl::opt<bool> DisablePPCConstHoist("disable-ppc-constant-hoisting",
  21 cl::desc("disable constant hoisting on PPC"), cl::init(false), cl::Hidden);
  22
  23 // This is currently only used for the data prefetch pass which is only enabled
  24 // for BG/Q by default.
  25 static cl::opt<unsigned>
  26 CacheLineSize("ppc-loop-prefetch-cache-line", cl::Hidden, cl::init(64),
  27               cl::desc("The loop prefetch cache line size"));
  28
  29 static cl::opt<bool>
  30 EnablePPCColdCC("ppc-enable-coldcc", cl::Hidden, cl::init(false),
  31                 cl::desc("Enable using coldcc calling conv for cold "
  32                          "internal functions"));
  33
  34 //===----------------------------------------------------------------------===//
  35 //
  36 // PPC cost model.
  37 //
  38 //===----------------------------------------------------------------------===//
  39
  40 TargetTransformInfo::PopcntSupportKind
  41 PPCTTIImpl::getPopcntSupport(unsigned TyWidth) {
  42   assert(isPowerOf2_32(TyWidth) && "Ty width must be power of 2");
  43   if (ST->hasPOPCNTD() != PPCSubtarget::POPCNTD_Unavailable && TyWidth <= 64)
  44     return ST->hasPOPCNTD() == PPCSubtarget::POPCNTD_Slow ?
  45              TTI::PSK_SlowHardware : TTI::PSK_FastHardware;
  46   return TTI::PSK_Software;
  47 }
  48
  49 int PPCTTIImpl::getIntImmCost(const APInt &Imm, Type *Ty) {
  50   if (DisablePPCConstHoist)
  51     return BaseT::getIntImmCost(Imm, Ty);
  52
  53   assert(Ty->isIntegerTy());
  54
  55   unsigned BitSize = Ty->getPrimitiveSizeInBits();
  56   if (BitSize == 0)
  57     return ~0U;
  58
  59   if (Imm == 0)
  60     return TTI::TCC_Free;
  61
  62   if (Imm.getBitWidth() <= 64) {
  63     if (isInt<16>(Imm.getSExtValue()))
  64       return TTI::TCC_Basic;
  65
  66     if (isInt<32>(Imm.getSExtValue())) {
  67       // A constant that can be materialized using lis.
  68       if ((Imm.getZExtValue() & 0xFFFF) == 0)
  69         return TTI::TCC_Basic;
  70
  71       return 2 * TTI::TCC_Basic;
  72     }
  73   }
  74
  75   return 4 * TTI::TCC_Basic;
  76 }
  77
  78 int PPCTTIImpl::getIntImmCost(Intrinsic::ID IID, unsigned Idx, const APInt &Imm,
  79                               Type *Ty) {
  80   if (DisablePPCConstHoist)
  81     return BaseT::getIntImmCost(IID, Idx, Imm, Ty);
  82
  83   assert(Ty->isIntegerTy());
  84
  85   unsigned BitSize = Ty->getPrimitiveSizeInBits();
  86   if (BitSize == 0)
  87     return ~0U;
  88
  89   switch (IID) {
  90   default:
  91     return TTI::TCC_Free;
  92   case Intrinsic::sadd_with_overflow:
  93   case Intrinsic::uadd_with_overflow:
  94   case Intrinsic::ssub_with_overflow:
  95   case Intrinsic::usub_with_overflow:
  96     if ((Idx == 1) && Imm.getBitWidth() <= 64 && isInt<16>(Imm.getSExtValue()))
  97       return TTI::TCC_Free;
  98     break;
  99   case Intrinsic::experimental_stackmap:
 100     if ((Idx < 2) || (Imm.getBitWidth() <= 64 && isInt<64>(Imm.getSExtValue())))
 101       return TTI::TCC_Free;
 102     break;
 103   case Intrinsic::experimental_patchpoint_void:
 104   case Intrinsic::experimental_patchpoint_i64:
 105     if ((Idx < 4) || (Imm.getBitWidth() <= 64 && isInt<64>(Imm.getSExtValue())))
 106       return TTI::TCC_Free;
 107     break;
 108   }
 109   return PPCTTIImpl::getIntImmCost(Imm, Ty);
 110 }
 111
 112 int PPCTTIImpl::getIntImmCost(unsigned Opcode, unsigned Idx, const APInt &Imm,
 113                               Type *Ty) {
 114   if (DisablePPCConstHoist)
 115     return BaseT::getIntImmCost(Opcode, Idx, Imm, Ty);
 116
 117   assert(Ty->isIntegerTy());
 118
 119   unsigned BitSize = Ty->getPrimitiveSizeInBits();
 120   if (BitSize == 0)
 121     return ~0U;
 122
 123   unsigned ImmIdx = ~0U;
 124   bool ShiftedFree = false, RunFree = false, UnsignedFree = false,
 125        ZeroFree = false;
 126   switch (Opcode) {
 127   default:
 128     return TTI::TCC_Free;
 129   case Instruction::GetElementPtr:
 130     // Always hoist the base address of a GetElementPtr. This prevents the
 131     // creation of new constants for every base constant that gets constant
 132     // folded with the offset.
 133     if (Idx == 0)
 134       return 2 * TTI::TCC_Basic;
 135     return TTI::TCC_Free;
 136   case Instruction::And:
 137     RunFree = true; // (for the rotate-and-mask instructions)
 138     LLVM_FALLTHROUGH;
 139   case Instruction::Add:
 140   case Instruction::Or:
 141   case Instruction::Xor:
 142     ShiftedFree = true;
 143     LLVM_FALLTHROUGH;
 144   case Instruction::Sub:
 145   case Instruction::Mul:
 146   case Instruction::Shl:
 147   case Instruction::LShr:
 148   case Instruction::AShr:
 149     ImmIdx = 1;
 150     break;
 151   case Instruction::ICmp:
 152     UnsignedFree = true;
 153     ImmIdx = 1;
 154     // Zero comparisons can use record-form instructions.
 155     LLVM_FALLTHROUGH;
 156   case Instruction::Select:
 157     ZeroFree = true;
 158     break;
 159   case Instruction::PHI:
 160   case Instruction::Call:
 161   case Instruction::Ret:
 162   case Instruction::Load:
 163   case Instruction::Store:
 164     break;
 165   }
 166
 167   if (ZeroFree && Imm == 0)
 168     return TTI::TCC_Free;
 169
 170   if (Idx == ImmIdx && Imm.getBitWidth() <= 64) {
 171     if (isInt<16>(Imm.getSExtValue()))
 172       return TTI::TCC_Free;
 173
 174     if (RunFree) {
 175       if (Imm.getBitWidth() <= 32 &&
 176           (isShiftedMask_32(Imm.getZExtValue()) ||
 177            isShiftedMask_32(~Imm.getZExtValue())))
 178         return TTI::TCC_Free;
 179
 180       if (ST->isPPC64() &&
 181           (isShiftedMask_64(Imm.getZExtValue()) ||
 182            isShiftedMask_64(~Imm.getZExtValue())))
 183         return TTI::TCC_Free;
 184     }
 185
 186     if (UnsignedFree && isUInt<16>(Imm.getZExtValue()))
 187       return TTI::TCC_Free;
 188
 189     if (ShiftedFree && (Imm.getZExtValue() & 0xFFFF) == 0)
 190       return TTI::TCC_Free;
 191   }
 192
 193   return PPCTTIImpl::getIntImmCost(Imm, Ty);
 194 }
 195
 196 unsigned PPCTTIImpl::getUserCost(const User *U,
 197                                  ArrayRef<const Value *> Operands) {
 198   if (U->getType()->isVectorTy()) {
 199     // Instructions that need to be split should cost more.
 200     std::pair<int, MVT> LT = TLI->getTypeLegalizationCost(DL, U->getType());
 201     return LT.first * BaseT::getUserCost(U, Operands);
 202   }
 203
 204   return BaseT::getUserCost(U, Operands);
 205 }
 206
 207 void PPCTTIImpl::getUnrollingPreferences(Loop *L, ScalarEvolution &SE,
 208                                          TTI::UnrollingPreferences &UP) {
 209   if (ST->getDarwinDirective() == PPC::DIR_A2) {
 210     // The A2 is in-order with a deep pipeline, and concatenation unrolling
 211     // helps expose latency-hiding opportunities to the instruction scheduler.
 212     UP.Partial = UP.Runtime = true;
 213
 214     // We unroll a lot on the A2 (hundreds of instructions), and the benefits
 215     // often outweigh the cost of a division to compute the trip count.
 216     UP.AllowExpensiveTripCount = true;
 217   }
 218
 219   BaseT::getUnrollingPreferences(L, SE, UP);
 220 }
 221
 222 // This function returns true to allow using coldcc calling convention.
 223 // Returning true results in coldcc being used for functions which are cold at
 224 // all call sites when the callers of the functions are not calling any other
 225 // non coldcc functions.
 226 bool PPCTTIImpl::useColdCCForColdCall(Function &F) {
 227   return EnablePPCColdCC;
 228 }
 229
 230 bool PPCTTIImpl::enableAggressiveInterleaving(bool LoopHasReductions) {
 231   // On the A2, always unroll aggressively. For QPX unaligned loads, we depend
 232   // on combining the loads generated for consecutive accesses, and failure to
 233   // do so is particularly expensive. This makes it much more likely (compared
 234   // to only using concatenation unrolling).
 235   if (ST->getDarwinDirective() == PPC::DIR_A2)
 236     return true;
 237
 238   return LoopHasReductions;
 239 }
 240
 241 const PPCTTIImpl::TTI::MemCmpExpansionOptions *
 242 PPCTTIImpl::enableMemCmpExpansion(bool IsZeroCmp) const {
 243   static const auto Options = []() {
 244     TTI::MemCmpExpansionOptions Options;
 245     Options.LoadSizes.push_back(8);
 246     Options.LoadSizes.push_back(4);
 247     Options.LoadSizes.push_back(2);
 248     Options.LoadSizes.push_back(1);
 249     return Options;
 250   }();
 251   return &Options;
 252 }
 253
 254 bool PPCTTIImpl::enableInterleavedAccessVectorization() {
 255   return true;
 256 }
 257
 258 unsigned PPCTTIImpl::getNumberOfRegisters(bool Vector) {
 259   if (Vector && !ST->hasAltivec() && !ST->hasQPX())
 260     return 0;
 261   return ST->hasVSX() ? 64 : 32;
 262 }
 263
 264 unsigned PPCTTIImpl::getRegisterBitWidth(bool Vector) const {
 265   if (Vector) {
 266     if (ST->hasQPX()) return 256;
 267     if (ST->hasAltivec()) return 128;
 268     return 0;
 269   }
 270
 271   if (ST->isPPC64())
 272     return 64;
 273   return 32;
 274
 275 }
 276
 277 unsigned PPCTTIImpl::getCacheLineSize() {
 278   // Check first if the user specified a custom line size.
 279   if (CacheLineSize.getNumOccurrences() > 0)
 280     return CacheLineSize;
 281
 282   // On P7, P8 or P9 we have a cache line size of 128.
 283   unsigned Directive = ST->getDarwinDirective();
 284   if (Directive == PPC::DIR_PWR7 || Directive == PPC::DIR_PWR8 ||
 285       Directive == PPC::DIR_PWR9)
 286     return 128;
 287
 288   // On other processors return a default of 64 bytes.
 289   return 64;
 290 }
 291
 292 unsigned PPCTTIImpl::getPrefetchDistance() {
 293   // This seems like a reasonable default for the BG/Q (this pass is enabled, by
 294   // default, only on the BG/Q).
 295   return 300;
 296 }
 297
 298 unsigned PPCTTIImpl::getMaxInterleaveFactor(unsigned VF) {
 299   unsigned Directive = ST->getDarwinDirective();
 300   // The 440 has no SIMD support, but floating-point instructions
 301   // have a 5-cycle latency, so unroll by 5x for latency hiding.
 302   if (Directive == PPC::DIR_440)
 303     return 5;
 304
 305   // The A2 has no SIMD support, but floating-point instructions
 306   // have a 6-cycle latency, so unroll by 6x for latency hiding.
 307   if (Directive == PPC::DIR_A2)
 308     return 6;
 309
 310   // FIXME: For lack of any better information, do no harm...
 311   if (Directive == PPC::DIR_E500mc || Directive == PPC::DIR_E5500)
 312     return 1;
 313
 314   // For P7 and P8, floating-point instructions have a 6-cycle latency and
 315   // there are two execution units, so unroll by 12x for latency hiding.
 316   // FIXME: the same for P9 as previous gen until POWER9 scheduling is ready
 317   if (Directive == PPC::DIR_PWR7 || Directive == PPC::DIR_PWR8 ||
 318       Directive == PPC::DIR_PWR9)
 319     return 12;
 320
 321   // For most things, modern systems have two execution units (and
 322   // out-of-order execution).
 323   return 2;
 324 }
 325
 326 // Adjust the cost of vector instructions on targets which there is overlap
 327 // between the vector and scalar units, thereby reducing the overall throughput
 328 // of vector code wrt. scalar code.
 329 int PPCTTIImpl::vectorCostAdjustment(int Cost, unsigned Opcode, Type *Ty1,
 330                                      Type *Ty2) {
 331   if (!ST->vectorsUseTwoUnits() || !Ty1->isVectorTy())
 332     return Cost;
 333
 334   std::pair<int, MVT> LT1 = TLI->getTypeLegalizationCost(DL, Ty1);
 335   // If type legalization involves splitting the vector, we don't want to
 336   // double the cost at every step - only the last step.
 337   if (LT1.first != 1 || !LT1.second.isVector())
 338     return Cost;
 339   int ISD = TLI->InstructionOpcodeToISD(Opcode);
 340   if (TLI->isOperationExpand(ISD, LT1.second))
 341     return Cost;
 342
 343   if (Ty2) {
 344     std::pair<int, MVT> LT2 = TLI->getTypeLegalizationCost(DL, Ty2);
 345     if (LT2.first != 1 || !LT2.second.isVector())
 346       return Cost;
 347   }
 348
 349   return Cost * 2;
 350 }
 351
 352 int PPCTTIImpl::getArithmeticInstrCost(
 353     unsigned Opcode, Type *Ty, TTI::OperandValueKind Op1Info,
 354     TTI::OperandValueKind Op2Info, TTI::OperandValueProperties Opd1PropInfo,
 355     TTI::OperandValueProperties Opd2PropInfo, ArrayRef<const Value *> Args) {
 356   assert(TLI->InstructionOpcodeToISD(Opcode) && "Invalid opcode");
 357
 358   // Fallback to the default implementation.
 359   int Cost = BaseT::getArithmeticInstrCost(Opcode, Ty, Op1Info, Op2Info,
 360                                            Opd1PropInfo, Opd2PropInfo);
 361   return vectorCostAdjustment(Cost, Opcode, Ty, nullptr);
 362 }
 363
 364 int PPCTTIImpl::getShuffleCost(TTI::ShuffleKind Kind, Type *Tp, int Index,
 365                                Type *SubTp) {
 366   // Legalize the type.
 367   std::pair<int, MVT> LT = TLI->getTypeLegalizationCost(DL, Tp);
 368
 369   // PPC, for both Altivec/VSX and QPX, support cheap arbitrary permutations
 370   // (at least in the sense that there need only be one non-loop-invariant
 371   // instruction). We need one such shuffle instruction for each actual
 372   // register (this is not true for arbitrary shuffles, but is true for the
 373   // structured types of shuffles covered by TTI::ShuffleKind).
 374   return vectorCostAdjustment(LT.first, Instruction::ShuffleVector, Tp,
 375                               nullptr);
 376 }
 377
 378 int PPCTTIImpl::getCastInstrCost(unsigned Opcode, Type *Dst, Type *Src,
 379                                  const Instruction *I) {
 380   assert(TLI->InstructionOpcodeToISD(Opcode) && "Invalid opcode");
 381
 382   int Cost = BaseT::getCastInstrCost(Opcode, Dst, Src);
 383   return vectorCostAdjustment(Cost, Opcode, Dst, Src);
 384 }
 385
 386 int PPCTTIImpl::getCmpSelInstrCost(unsigned Opcode, Type *ValTy, Type *CondTy,
 387                                    const Instruction *I) {
 388   int Cost = BaseT::getCmpSelInstrCost(Opcode, ValTy, CondTy, I);
 389   return vectorCostAdjustment(Cost, Opcode, ValTy, nullptr);
 390 }
 391
 392 int PPCTTIImpl::getVectorInstrCost(unsigned Opcode, Type *Val, unsigned Index) {
 393   assert(Val->isVectorTy() && "This must be a vector type");
 394
 395   int ISD = TLI->InstructionOpcodeToISD(Opcode);
 396   assert(ISD && "Invalid opcode");
 397
 398   int Cost = BaseT::getVectorInstrCost(Opcode, Val, Index);
 399   Cost = vectorCostAdjustment(Cost, Opcode, Val, nullptr);
 400
 401   if (ST->hasVSX() && Val->getScalarType()->isDoubleTy()) {
 402     // Double-precision scalars are already located in index #0 (or #1 if LE).
 403     if (ISD == ISD::EXTRACT_VECTOR_ELT && Index == ST->isLittleEndian() ? 1 : 0)
 404       return 0;
 405
 406     return Cost;
 407
 408   } else if (ST->hasQPX() && Val->getScalarType()->isFloatingPointTy()) {
 409     // Floating point scalars are already located in index #0.
 410     if (Index == 0)
 411       return 0;
 412
 413     return Cost;
 414   }
 415
 416   // Estimated cost of a load-hit-store delay.  This was obtained
 417   // experimentally as a minimum needed to prevent unprofitable
 418   // vectorization for the paq8p benchmark.  It may need to be
 419   // raised further if other unprofitable cases remain.
 420   unsigned LHSPenalty = 2;
 421   if (ISD == ISD::INSERT_VECTOR_ELT)
 422     LHSPenalty += 7;
 423
 424   // Vector element insert/extract with Altivec is very expensive,
 425   // because they require store and reload with the attendant
 426   // processor stall for load-hit-store.  Until VSX is available,
 427   // these need to be estimated as very costly.
 428   if (ISD == ISD::EXTRACT_VECTOR_ELT ||
 429       ISD == ISD::INSERT_VECTOR_ELT)
 430     return LHSPenalty + Cost;
 431
 432   return Cost;
 433 }
 434
 435 int PPCTTIImpl::getMemoryOpCost(unsigned Opcode, Type *Src, unsigned Alignment,
 436                                 unsigned AddressSpace, const Instruction *I) {
 437   // Legalize the type.
 438   std::pair<int, MVT> LT = TLI->getTypeLegalizationCost(DL, Src);
 439   assert((Opcode == Instruction::Load || Opcode == Instruction::Store) &&
 440          "Invalid Opcode");
 441
 442   int Cost = BaseT::getMemoryOpCost(Opcode, Src, Alignment, AddressSpace);
 443   Cost = vectorCostAdjustment(Cost, Opcode, Src, nullptr);
 444
 445   bool IsAltivecType = ST->hasAltivec() &&
 446                        (LT.second == MVT::v16i8 || LT.second == MVT::v8i16 ||
 447                         LT.second == MVT::v4i32 || LT.second == MVT::v4f32);
 448   bool IsVSXType = ST->hasVSX() &&
 449                    (LT.second == MVT::v2f64 || LT.second == MVT::v2i64);
 450   bool IsQPXType = ST->hasQPX() &&
 451                    (LT.second == MVT::v4f64 || LT.second == MVT::v4f32);
 452
 453   // VSX has 32b/64b load instructions. Legalization can handle loading of
 454   // 32b/64b to VSR correctly and cheaply. But BaseT::getMemoryOpCost and
 455   // PPCTargetLowering can't compute the cost appropriately. So here we
 456   // explicitly check this case.
 457   unsigned MemBytes = Src->getPrimitiveSizeInBits();
 458   if (Opcode == Instruction::Load && ST->hasVSX() && IsAltivecType &&
 459       (MemBytes == 64 || (ST->hasP8Vector() && MemBytes == 32)))
 460     return 1;
 461
 462   // Aligned loads and stores are easy.
 463   unsigned SrcBytes = LT.second.getStoreSize();
 464   if (!SrcBytes || !Alignment || Alignment >= SrcBytes)
 465     return Cost;
 466
 467   // If we can use the permutation-based load sequence, then this is also
 468   // relatively cheap (not counting loop-invariant instructions): one load plus
 469   // one permute (the last load in a series has extra cost, but we're
 470   // neglecting that here). Note that on the P7, we could do unaligned loads
 471   // for Altivec types using the VSX instructions, but that's more expensive
 472   // than using the permutation-based load sequence. On the P8, that's no
 473   // longer true.
 474   if (Opcode == Instruction::Load &&
 475       ((!ST->hasP8Vector() && IsAltivecType) || IsQPXType) &&
 476       Alignment >= LT.second.getScalarType().getStoreSize())
 477     return Cost + LT.first; // Add the cost of the permutations.
 478
 479   // For VSX, we can do unaligned loads and stores on Altivec/VSX types. On the
 480   // P7, unaligned vector loads are more expensive than the permutation-based
 481   // load sequence, so that might be used instead, but regardless, the net cost
 482   // is about the same (not counting loop-invariant instructions).
 483   if (IsVSXType || (ST->hasVSX() && IsAltivecType))
 484     return Cost;
 485
 486   // Newer PPC supports unaligned memory access.
 487   if (TLI->allowsMisalignedMemoryAccesses(LT.second, 0))
 488     return Cost;
 489
 490   // PPC in general does not support unaligned loads and stores. They'll need
 491   // to be decomposed based on the alignment factor.
 492
 493   // Add the cost of each scalar load or store.
 494   Cost += LT.first*(SrcBytes/Alignment-1);
 495
 496   // For a vector type, there is also scalarization overhead (only for
 497   // stores, loads are expanded using the vector-load + permutation sequence,
 498   // which is much less expensive).
 499   if (Src->isVectorTy() && Opcode == Instruction::Store)
 500     for (int i = 0, e = Src->getVectorNumElements(); i < e; ++i)
 501       Cost += getVectorInstrCost(Instruction::ExtractElement, Src, i);
 502
 503   return Cost;
 504 }
 505
 506 int PPCTTIImpl::getInterleavedMemoryOpCost(unsigned Opcode, Type *VecTy,
 507                                            unsigned Factor,
 508                                            ArrayRef<unsigned> Indices,
 509                                            unsigned Alignment,
 510                                            unsigned AddressSpace,
 511                                            bool UseMaskForCond,
 512                                            bool UseMaskForGaps) {
 513   if (UseMaskForCond || UseMaskForGaps)
 514     return BaseT::getInterleavedMemoryOpCost(Opcode, VecTy, Factor, Indices,
 515                                              Alignment, AddressSpace,
 516                                              UseMaskForCond, UseMaskForGaps);
 517
 518   assert(isa<VectorType>(VecTy) &&
 519          "Expect a vector type for interleaved memory op");
 520
 521   // Legalize the type.
 522   std::pair<int, MVT> LT = TLI->getTypeLegalizationCost(DL, VecTy);
 523
 524   // Firstly, the cost of load/store operation.
 525   int Cost = getMemoryOpCost(Opcode, VecTy, Alignment, AddressSpace);
 526
 527   // PPC, for both Altivec/VSX and QPX, support cheap arbitrary permutations
 528   // (at least in the sense that there need only be one non-loop-invariant
 529   // instruction). For each result vector, we need one shuffle per incoming
 530   // vector (except that the first shuffle can take two incoming vectors
 531   // because it does not need to take itself).
 532   Cost += Factor*(LT.first-1);
 533
 534   return Cost;
 535 }
 536