lib/Target/Hexagon/HexagonStoreWidening.cpp

   1 //===- HexagonStoreWidening.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 // Replace sequences of "narrow" stores to adjacent memory locations with
   9 // a fewer "wide" stores that have the same effect.
  10 // For example, replace:
  11 //   S4_storeirb_io  %100, 0, 0   ; store-immediate-byte
  12 //   S4_storeirb_io  %100, 1, 0   ; store-immediate-byte
  13 // with
  14 //   S4_storeirh_io  %100, 0, 0   ; store-immediate-halfword
  15 // The above is the general idea.  The actual cases handled by the code
  16 // may be a bit more complex.
  17 // The purpose of this pass is to reduce the number of outstanding stores,
  18 // or as one could say, "reduce store queue pressure".  Also, wide stores
  19 // mean fewer stores, and since there are only two memory instructions allowed
  20 // per packet, it also means fewer packets, and ultimately fewer cycles.
  21 //===---------------------------------------------------------------------===//
  22
  23 #define DEBUG_TYPE "hexagon-widen-stores"
  24
  25 #include "HexagonInstrInfo.h"
  26 #include "HexagonRegisterInfo.h"
  27 #include "HexagonSubtarget.h"
  28 #include "llvm/ADT/SmallPtrSet.h"
  29 #include "llvm/Analysis/AliasAnalysis.h"
  30 #include "llvm/Analysis/MemoryLocation.h"
  31 #include "llvm/CodeGen/MachineBasicBlock.h"
  32 #include "llvm/CodeGen/MachineFunction.h"
  33 #include "llvm/CodeGen/MachineFunctionPass.h"
  34 #include "llvm/CodeGen/MachineInstr.h"
  35 #include "llvm/CodeGen/MachineInstrBuilder.h"
  36 #include "llvm/CodeGen/MachineMemOperand.h"
  37 #include "llvm/CodeGen/MachineOperand.h"
  38 #include "llvm/CodeGen/MachineRegisterInfo.h"
  39 #include "llvm/IR/DebugLoc.h"
  40 #include "llvm/MC/MCInstrDesc.h"
  41 #include "llvm/Pass.h"
  42 #include "llvm/Support/Debug.h"
  43 #include "llvm/Support/ErrorHandling.h"
  44 #include "llvm/Support/MathExtras.h"
  45 #include "llvm/Support/raw_ostream.h"
  46 #include <algorithm>
  47 #include <cassert>
  48 #include <cstdint>
  49 #include <iterator>
  50 #include <vector>
  51
  52 using namespace llvm;
  53
  54 namespace llvm {
  55
  56 FunctionPass *createHexagonStoreWidening();
  57 void initializeHexagonStoreWideningPass(PassRegistry&);
  58
  59 } // end namespace llvm
  60
  61 namespace {
  62
  63   struct HexagonStoreWidening : public MachineFunctionPass {
  64     const HexagonInstrInfo      *TII;
  65     const HexagonRegisterInfo   *TRI;
  66     const MachineRegisterInfo   *MRI;
  67     AliasAnalysis               *AA;
  68     MachineFunction             *MF;
  69
  70   public:
  71     static char ID;
  72
  73     HexagonStoreWidening() : MachineFunctionPass(ID) {
  74       initializeHexagonStoreWideningPass(*PassRegistry::getPassRegistry());
  75     }
  76
  77     bool runOnMachineFunction(MachineFunction &MF) override;
  78
  79     StringRef getPassName() const override { return "Hexagon Store Widening"; }
  80
  81     void getAnalysisUsage(AnalysisUsage &AU) const override {
  82       AU.addRequired<AAResultsWrapperPass>();
  83       AU.addPreserved<AAResultsWrapperPass>();
  84       MachineFunctionPass::getAnalysisUsage(AU);
  85     }
  86
  87     static bool handledStoreType(const MachineInstr *MI);
  88
  89   private:
  90     static const int MaxWideSize = 4;
  91
  92     using InstrGroup = std::vector<MachineInstr *>;
  93     using InstrGroupList = std::vector<InstrGroup>;
  94
  95     bool instrAliased(InstrGroup &Stores, const MachineMemOperand &MMO);
  96     bool instrAliased(InstrGroup &Stores, const MachineInstr *MI);
  97     void createStoreGroup(MachineInstr *BaseStore, InstrGroup::iterator Begin,
  98         InstrGroup::iterator End, InstrGroup &Group);
  99     void createStoreGroups(MachineBasicBlock &MBB,
 100         InstrGroupList &StoreGroups);
 101     bool processBasicBlock(MachineBasicBlock &MBB);
 102     bool processStoreGroup(InstrGroup &Group);
 103     bool selectStores(InstrGroup::iterator Begin, InstrGroup::iterator End,
 104         InstrGroup &OG, unsigned &TotalSize, unsigned MaxSize);
 105     bool createWideStores(InstrGroup &OG, InstrGroup &NG, unsigned TotalSize);
 106     bool replaceStores(InstrGroup &OG, InstrGroup &NG);
 107     bool storesAreAdjacent(const MachineInstr *S1, const MachineInstr *S2);
 108   };
 109
 110 } // end anonymous namespace
 111
 112 char HexagonStoreWidening::ID = 0;
 113
 114 INITIALIZE_PASS_BEGIN(HexagonStoreWidening, "hexagon-widen-stores",
 115                 "Hexason Store Widening", false, false)
 116 INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
 117 INITIALIZE_PASS_END(HexagonStoreWidening, "hexagon-widen-stores",
 118                 "Hexagon Store Widening", false, false)
 119
 120 // Some local helper functions...
 121 static unsigned getBaseAddressRegister(const MachineInstr *MI) {
 122   const MachineOperand &MO = MI->getOperand(0);
 123   assert(MO.isReg() && "Expecting register operand");
 124   return MO.getReg();
 125 }
 126
 127 static int64_t getStoreOffset(const MachineInstr *MI) {
 128   unsigned OpC = MI->getOpcode();
 129   assert(HexagonStoreWidening::handledStoreType(MI) && "Unhandled opcode");
 130
 131   switch (OpC) {
 132     case Hexagon::S4_storeirb_io:
 133     case Hexagon::S4_storeirh_io:
 134     case Hexagon::S4_storeiri_io: {
 135       const MachineOperand &MO = MI->getOperand(1);
 136       assert(MO.isImm() && "Expecting immediate offset");
 137       return MO.getImm();
 138     }
 139   }
 140   dbgs() << *MI;
 141   llvm_unreachable("Store offset calculation missing for a handled opcode");
 142   return 0;
 143 }
 144
 145 static const MachineMemOperand &getStoreTarget(const MachineInstr *MI) {
 146   assert(!MI->memoperands_empty() && "Expecting memory operands");
 147   return **MI->memoperands_begin();
 148 }
 149
 150 // Filtering function: any stores whose opcodes are not "approved" of by
 151 // this function will not be subjected to widening.
 152 inline bool HexagonStoreWidening::handledStoreType(const MachineInstr *MI) {
 153   // For now, only handle stores of immediate values.
 154   // Also, reject stores to stack slots.
 155   unsigned Opc = MI->getOpcode();
 156   switch (Opc) {
 157     case Hexagon::S4_storeirb_io:
 158     case Hexagon::S4_storeirh_io:
 159     case Hexagon::S4_storeiri_io:
 160       // Base address must be a register. (Implement FI later.)
 161       return MI->getOperand(0).isReg();
 162     default:
 163       return false;
 164   }
 165 }
 166
 167 // Check if the machine memory operand MMO is aliased with any of the
 168 // stores in the store group Stores.
 169 bool HexagonStoreWidening::instrAliased(InstrGroup &Stores,
 170       const MachineMemOperand &MMO) {
 171   if (!MMO.getValue())
 172     return true;
 173
 174   MemoryLocation L(MMO.getValue(), MMO.getSize(), MMO.getAAInfo());
 175
 176   for (auto SI : Stores) {
 177     const MachineMemOperand &SMO = getStoreTarget(SI);
 178     if (!SMO.getValue())
 179       return true;
 180
 181     MemoryLocation SL(SMO.getValue(), SMO.getSize(), SMO.getAAInfo());
 182     if (AA->alias(L, SL))
 183       return true;
 184   }
 185
 186   return false;
 187 }
 188
 189 // Check if the machine instruction MI accesses any storage aliased with
 190 // any store in the group Stores.
 191 bool HexagonStoreWidening::instrAliased(InstrGroup &Stores,
 192       const MachineInstr *MI) {
 193   for (auto &I : MI->memoperands())
 194     if (instrAliased(Stores, *I))
 195       return true;
 196   return false;
 197 }
 198
 199 // Inspect a machine basic block, and generate store groups out of stores
 200 // encountered in the block.
 201 //
 202 // A store group is a group of stores that use the same base register,
 203 // and which can be reordered within that group without altering the
 204 // semantics of the program.  A single store group could be widened as
 205 // a whole, if there existed a single store instruction with the same
 206 // semantics as the entire group.  In many cases, a single store group
 207 // may need more than one wide store.
 208 void HexagonStoreWidening::createStoreGroups(MachineBasicBlock &MBB,
 209       InstrGroupList &StoreGroups) {
 210   InstrGroup AllInsns;
 211
 212   // Copy all instruction pointers from the basic block to a temporary
 213   // list.  This will allow operating on the list, and modifying its
 214   // elements without affecting the basic block.
 215   for (auto &I : MBB)
 216     AllInsns.push_back(&I);
 217
 218   // Traverse all instructions in the AllInsns list, and if we encounter
 219   // a store, then try to create a store group starting at that instruction
 220   // i.e. a sequence of independent stores that can be widened.
 221   for (auto I = AllInsns.begin(), E = AllInsns.end(); I != E; ++I) {
 222     MachineInstr *MI = *I;
 223     // Skip null pointers (processed instructions).
 224     if (!MI || !handledStoreType(MI))
 225       continue;
 226
 227     // Found a store.  Try to create a store group.
 228     InstrGroup G;
 229     createStoreGroup(MI, I+1, E, G);
 230     if (G.size() > 1)
 231       StoreGroups.push_back(G);
 232   }
 233 }
 234
 235 // Create a single store group.  The stores need to be independent between
 236 // themselves, and also there cannot be other instructions between them
 237 // that could read or modify storage being stored into.
 238 void HexagonStoreWidening::createStoreGroup(MachineInstr *BaseStore,
 239       InstrGroup::iterator Begin, InstrGroup::iterator End, InstrGroup &Group) {
 240   assert(handledStoreType(BaseStore) && "Unexpected instruction");
 241   unsigned BaseReg = getBaseAddressRegister(BaseStore);
 242   InstrGroup Other;
 243
 244   Group.push_back(BaseStore);
 245
 246   for (auto I = Begin; I != End; ++I) {
 247     MachineInstr *MI = *I;
 248     if (!MI)
 249       continue;
 250
 251     if (handledStoreType(MI)) {
 252       // If this store instruction is aliased with anything already in the
 253       // group, terminate the group now.
 254       if (instrAliased(Group, getStoreTarget(MI)))
 255         return;
 256       // If this store is aliased to any of the memory instructions we have
 257       // seen so far (that are not a part of this group), terminate the group.
 258       if (instrAliased(Other, getStoreTarget(MI)))
 259         return;
 260
 261       unsigned BR = getBaseAddressRegister(MI);
 262       if (BR == BaseReg) {
 263         Group.push_back(MI);
 264         *I = nullptr;
 265         continue;
 266       }
 267     }
 268
 269     // Assume calls are aliased to everything.
 270     if (MI->isCall() || MI->hasUnmodeledSideEffects())
 271       return;
 272
 273     if (MI->mayLoad() || MI->mayStore()) {
 274       if (MI->hasOrderedMemoryRef() || instrAliased(Group, MI))
 275         return;
 276       Other.push_back(MI);
 277     }
 278   } // for
 279 }
 280
 281 // Check if store instructions S1 and S2 are adjacent.  More precisely,
 282 // S2 has to access memory immediately following that accessed by S1.
 283 bool HexagonStoreWidening::storesAreAdjacent(const MachineInstr *S1,
 284       const MachineInstr *S2) {
 285   if (!handledStoreType(S1) || !handledStoreType(S2))
 286     return false;
 287
 288   const MachineMemOperand &S1MO = getStoreTarget(S1);
 289
 290   // Currently only handling immediate stores.
 291   int Off1 = S1->getOperand(1).getImm();
 292   int Off2 = S2->getOperand(1).getImm();
 293
 294   return (Off1 >= 0) ? Off1+S1MO.getSize() == unsigned(Off2)
 295                      : int(Off1+S1MO.getSize()) == Off2;
 296 }
 297
 298 /// Given a sequence of adjacent stores, and a maximum size of a single wide
 299 /// store, pick a group of stores that  can be replaced by a single store
 300 /// of size not exceeding MaxSize.  The selected sequence will be recorded
 301 /// in OG ("old group" of instructions).
 302 /// OG should be empty on entry, and should be left empty if the function
 303 /// fails.
 304 bool HexagonStoreWidening::selectStores(InstrGroup::iterator Begin,
 305       InstrGroup::iterator End, InstrGroup &OG, unsigned &TotalSize,
 306       unsigned MaxSize) {
 307   assert(Begin != End && "No instructions to analyze");
 308   assert(OG.empty() && "Old group not empty on entry");
 309
 310   if (std::distance(Begin, End) <= 1)
 311     return false;
 312
 313   MachineInstr *FirstMI = *Begin;
 314   assert(!FirstMI->memoperands_empty() && "Expecting some memory operands");
 315   const MachineMemOperand &FirstMMO = getStoreTarget(FirstMI);
 316   unsigned Alignment = FirstMMO.getAlignment();
 317   unsigned SizeAccum = FirstMMO.getSize();
 318   unsigned FirstOffset = getStoreOffset(FirstMI);
 319
 320   // The initial value of SizeAccum should always be a power of 2.
 321   assert(isPowerOf2_32(SizeAccum) && "First store size not a power of 2");
 322
 323   // If the size of the first store equals to or exceeds the limit, do nothing.
 324   if (SizeAccum >= MaxSize)
 325     return false;
 326
 327   // If the size of the first store is greater than or equal to the address
 328   // stored to, then the store cannot be made any wider.
 329   if (SizeAccum >= Alignment)
 330     return false;
 331
 332   // The offset of a store will put restrictions on how wide the store can be.
 333   // Offsets in stores of size 2^n bytes need to have the n lowest bits be 0.
 334   // If the first store already exhausts the offset limits, quit.  Test this
 335   // by checking if the next wider size would exceed the limit.
 336   if ((2*SizeAccum-1) & FirstOffset)
 337     return false;
 338
 339   OG.push_back(FirstMI);
 340   MachineInstr *S1 = FirstMI;
 341
 342   // Pow2Num will be the largest number of elements in OG such that the sum
 343   // of sizes of stores 0...Pow2Num-1 will be a power of 2.
 344   unsigned Pow2Num = 1;
 345   unsigned Pow2Size = SizeAccum;
 346
 347   // Be greedy: keep accumulating stores as long as they are to adjacent
 348   // memory locations, and as long as the total number of bytes stored
 349   // does not exceed the limit (MaxSize).
 350   // Keep track of when the total size covered is a power of 2, since
 351   // this is a size a single store can cover.
 352   for (InstrGroup::iterator I = Begin + 1; I != End; ++I) {
 353     MachineInstr *S2 = *I;
 354     // Stores are sorted, so if S1 and S2 are not adjacent, there won't be
 355     // any other store to fill the "hole".
 356     if (!storesAreAdjacent(S1, S2))
 357       break;
 358
 359     unsigned S2Size = getStoreTarget(S2).getSize();
 360     if (SizeAccum + S2Size > std::min(MaxSize, Alignment))
 361       break;
 362
 363     OG.push_back(S2);
 364     SizeAccum += S2Size;
 365     if (isPowerOf2_32(SizeAccum)) {
 366       Pow2Num = OG.size();
 367       Pow2Size = SizeAccum;
 368     }
 369     if ((2*Pow2Size-1) & FirstOffset)
 370       break;
 371
 372     S1 = S2;
 373   }
 374
 375   // The stores don't add up to anything that can be widened.  Clean up.
 376   if (Pow2Num <= 1) {
 377     OG.clear();
 378     return false;
 379   }
 380
 381   // Only leave the stored being widened.
 382   OG.resize(Pow2Num);
 383   TotalSize = Pow2Size;
 384   return true;
 385 }
 386
 387 /// Given an "old group" OG of stores, create a "new group" NG of instructions
 388 /// to replace them.  Ideally, NG would only have a single instruction in it,
 389 /// but that may only be possible for store-immediate.
 390 bool HexagonStoreWidening::createWideStores(InstrGroup &OG, InstrGroup &NG,
 391       unsigned TotalSize) {
 392   // XXX Current limitations:
 393   // - only expect stores of immediate values in OG,
 394   // - only handle a TotalSize of up to 4.
 395
 396   if (TotalSize > 4)
 397     return false;
 398
 399   unsigned Acc = 0;  // Value accumulator.
 400   unsigned Shift = 0;
 401
 402   for (InstrGroup::iterator I = OG.begin(), E = OG.end(); I != E; ++I) {
 403     MachineInstr *MI = *I;
 404     const MachineMemOperand &MMO = getStoreTarget(MI);
 405     MachineOperand &SO = MI->getOperand(2);  // Source.
 406     assert(SO.isImm() && "Expecting an immediate operand");
 407
 408     unsigned NBits = MMO.getSize()*8;
 409     unsigned Mask = (0xFFFFFFFFU >> (32-NBits));
 410     unsigned Val = (SO.getImm() & Mask) << Shift;
 411     Acc |= Val;
 412     Shift += NBits;
 413   }
 414
 415   MachineInstr *FirstSt = OG.front();
 416   DebugLoc DL = OG.back()->getDebugLoc();
 417   const MachineMemOperand &OldM = getStoreTarget(FirstSt);
 418   MachineMemOperand *NewM =
 419     MF->getMachineMemOperand(OldM.getPointerInfo(), OldM.getFlags(),
 420                              TotalSize, OldM.getAlignment(),
 421                              OldM.getAAInfo());
 422
 423   if (Acc < 0x10000) {
 424     // Create mem[hw] = #Acc
 425     unsigned WOpc = (TotalSize == 2) ? Hexagon::S4_storeirh_io :
 426                     (TotalSize == 4) ? Hexagon::S4_storeiri_io : 0;
 427     assert(WOpc && "Unexpected size");
 428
 429     int Val = (TotalSize == 2) ? int16_t(Acc) : int(Acc);
 430     const MCInstrDesc &StD = TII->get(WOpc);
 431     MachineOperand &MR = FirstSt->getOperand(0);
 432     int64_t Off = FirstSt->getOperand(1).getImm();
 433     MachineInstr *StI =
 434         BuildMI(*MF, DL, StD)
 435             .addReg(MR.getReg(), getKillRegState(MR.isKill()), MR.getSubReg())
 436             .addImm(Off)
 437             .addImm(Val);
 438     StI->addMemOperand(*MF, NewM);
 439     NG.push_back(StI);
 440   } else {
 441     // Create vreg = A2_tfrsi #Acc; mem[hw] = vreg
 442     const MCInstrDesc &TfrD = TII->get(Hexagon::A2_tfrsi);
 443     const TargetRegisterClass *RC = TII->getRegClass(TfrD, 0, TRI, *MF);
 444     unsigned VReg = MF->getRegInfo().createVirtualRegister(RC);
 445     MachineInstr *TfrI = BuildMI(*MF, DL, TfrD, VReg)
 446                            .addImm(int(Acc));
 447     NG.push_back(TfrI);
 448
 449     unsigned WOpc = (TotalSize == 2) ? Hexagon::S2_storerh_io :
 450                     (TotalSize == 4) ? Hexagon::S2_storeri_io : 0;
 451     assert(WOpc && "Unexpected size");
 452
 453     const MCInstrDesc &StD = TII->get(WOpc);
 454     MachineOperand &MR = FirstSt->getOperand(0);
 455     int64_t Off = FirstSt->getOperand(1).getImm();
 456     MachineInstr *StI =
 457         BuildMI(*MF, DL, StD)
 458             .addReg(MR.getReg(), getKillRegState(MR.isKill()), MR.getSubReg())
 459             .addImm(Off)
 460             .addReg(VReg, RegState::Kill);
 461     StI->addMemOperand(*MF, NewM);
 462     NG.push_back(StI);
 463   }
 464
 465   return true;
 466 }
 467
 468 // Replace instructions from the old group OG with instructions from the
 469 // new group NG.  Conceptually, remove all instructions in OG, and then
 470 // insert all instructions in NG, starting at where the first instruction
 471 // from OG was (in the order in which they appeared in the basic block).
 472 // (The ordering in OG does not have to match the order in the basic block.)
 473 bool HexagonStoreWidening::replaceStores(InstrGroup &OG, InstrGroup &NG) {
 474   LLVM_DEBUG({
 475     dbgs() << "Replacing:\n";
 476     for (auto I : OG)
 477       dbgs() << "  " << *I;
 478     dbgs() << "with\n";
 479     for (auto I : NG)
 480       dbgs() << "  " << *I;
 481   });
 482
 483   MachineBasicBlock *MBB = OG.back()->getParent();
 484   MachineBasicBlock::iterator InsertAt = MBB->end();
 485
 486   // Need to establish the insertion point.  The best one is right before
 487   // the first store in the OG, but in the order in which the stores occur
 488   // in the program list.  Since the ordering in OG does not correspond
 489   // to the order in the program list, we need to do some work to find
 490   // the insertion point.
 491
 492   // Create a set of all instructions in OG (for quick lookup).
 493   SmallPtrSet<MachineInstr*, 4> InstrSet;
 494   for (auto I : OG)
 495     InstrSet.insert(I);
 496
 497   // Traverse the block, until we hit an instruction from OG.
 498   for (auto &I : *MBB) {
 499     if (InstrSet.count(&I)) {
 500       InsertAt = I;
 501       break;
 502     }
 503   }
 504
 505   assert((InsertAt != MBB->end()) && "Cannot locate any store from the group");
 506
 507   bool AtBBStart = false;
 508
 509   // InsertAt points at the first instruction that will be removed.  We need
 510   // to move it out of the way, so it remains valid after removing all the
 511   // old stores, and so we are able to recover it back to the proper insertion
 512   // position.
 513   if (InsertAt != MBB->begin())
 514     --InsertAt;
 515   else
 516     AtBBStart = true;
 517
 518   for (auto I : OG)
 519     I->eraseFromParent();
 520
 521   if (!AtBBStart)
 522     ++InsertAt;
 523   else
 524     InsertAt = MBB->begin();
 525
 526   for (auto I : NG)
 527     MBB->insert(InsertAt, I);
 528
 529   return true;
 530 }
 531
 532 // Break up the group into smaller groups, each of which can be replaced by
 533 // a single wide store.  Widen each such smaller group and replace the old
 534 // instructions with the widened ones.
 535 bool HexagonStoreWidening::processStoreGroup(InstrGroup &Group) {
 536   bool Changed = false;
 537   InstrGroup::iterator I = Group.begin(), E = Group.end();
 538   InstrGroup OG, NG;   // Old and new groups.
 539   unsigned CollectedSize;
 540
 541   while (I != E) {
 542     OG.clear();
 543     NG.clear();
 544
 545     bool Succ = selectStores(I++, E, OG, CollectedSize, MaxWideSize) &&
 546                 createWideStores(OG, NG, CollectedSize)              &&
 547                 replaceStores(OG, NG);
 548     if (!Succ)
 549       continue;
 550
 551     assert(OG.size() > 1 && "Created invalid group");
 552     assert(distance(I, E)+1 >= int(OG.size()) && "Too many elements");
 553     I += OG.size()-1;
 554
 555     Changed = true;
 556   }
 557
 558   return Changed;
 559 }
 560
 561 // Process a single basic block: create the store groups, and replace them
 562 // with the widened stores, if possible.  Processing of each basic block
 563 // is independent from processing of any other basic block.  This transfor-
 564 // mation could be stopped after having processed any basic block without
 565 // any ill effects (other than not having performed widening in the unpro-
 566 // cessed blocks).  Also, the basic blocks can be processed in any order.
 567 bool HexagonStoreWidening::processBasicBlock(MachineBasicBlock &MBB) {
 568   InstrGroupList SGs;
 569   bool Changed = false;
 570
 571   createStoreGroups(MBB, SGs);
 572
 573   auto Less = [] (const MachineInstr *A, const MachineInstr *B) -> bool {
 574     return getStoreOffset(A) < getStoreOffset(B);
 575   };
 576   for (auto &G : SGs) {
 577     assert(G.size() > 1 && "Store group with fewer than 2 elements");
 578     llvm::sort(G, Less);
 579
 580     Changed |= processStoreGroup(G);
 581   }
 582
 583   return Changed;
 584 }
 585
 586 bool HexagonStoreWidening::runOnMachineFunction(MachineFunction &MFn) {
 587   if (skipFunction(MFn.getFunction()))
 588     return false;
 589
 590   MF = &MFn;
 591   auto &ST = MFn.getSubtarget<HexagonSubtarget>();
 592   TII = ST.getInstrInfo();
 593   TRI = ST.getRegisterInfo();
 594   MRI = &MFn.getRegInfo();
 595   AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
 596
 597   bool Changed = false;
 598
 599   for (auto &B : MFn)
 600     Changed |= processBasicBlock(B);
 601
 602   return Changed;
 603 }
 604
 605 FunctionPass *llvm::createHexagonStoreWidening() {
 606   return new HexagonStoreWidening();
 607 }