llvm/lib/Transforms/Utils/LowerMemIntrinsics.cpp

   1 //===- LowerMemIntrinsics.cpp ----------------------------------*- C++ -*--===//
   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 "llvm/Transforms/Utils/LowerMemIntrinsics.h"
  10 #include "llvm/Analysis/ScalarEvolution.h"
  11 #include "llvm/Analysis/TargetTransformInfo.h"
  12 #include "llvm/IR/IRBuilder.h"
  13 #include "llvm/IR/IntrinsicInst.h"
  14 #include "llvm/IR/MDBuilder.h"
  15 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
  16
  17 using namespace llvm;
  18
  19 void llvm::createMemCpyLoopKnownSize(Instruction *InsertBefore, Value *SrcAddr,
  20                                      Value *DstAddr, ConstantInt *CopyLen,
  21                                      Align SrcAlign, Align DstAlign,
  22                                      bool SrcIsVolatile, bool DstIsVolatile,
  23                                      bool CanOverlap,
  24                                      const TargetTransformInfo &TTI,
  25                                      Optional<uint32_t> AtomicElementSize) {
  26   // No need to expand zero length copies.
  27   if (CopyLen->isZero())
  28     return;
  29
  30   BasicBlock *PreLoopBB = InsertBefore->getParent();
  31   BasicBlock *PostLoopBB = nullptr;
  32   Function *ParentFunc = PreLoopBB->getParent();
  33   LLVMContext &Ctx = PreLoopBB->getContext();
  34   const DataLayout &DL = ParentFunc->getParent()->getDataLayout();
  35   MDBuilder MDB(Ctx);
  36   MDNode *NewDomain = MDB.createAnonymousAliasScopeDomain("MemCopyDomain");
  37   StringRef Name = "MemCopyAliasScope";
  38   MDNode *NewScope = MDB.createAnonymousAliasScope(NewDomain, Name);
  39
  40   unsigned SrcAS = cast<PointerType>(SrcAddr->getType())->getAddressSpace();
  41   unsigned DstAS = cast<PointerType>(DstAddr->getType())->getAddressSpace();
  42
  43   Type *TypeOfCopyLen = CopyLen->getType();
  44   Type *LoopOpType = TTI.getMemcpyLoopLoweringType(
  45       Ctx, CopyLen, SrcAS, DstAS, SrcAlign.value(), DstAlign.value(),
  46       AtomicElementSize);
  47   assert((!AtomicElementSize || !LoopOpType->isVectorTy()) &&
  48          "Atomic memcpy lowering is not supported for vector operand type");
  49
  50   unsigned LoopOpSize = DL.getTypeStoreSize(LoopOpType);
  51   assert((!AtomicElementSize || LoopOpSize % *AtomicElementSize == 0) &&
  52       "Atomic memcpy lowering is not supported for selected operand size");
  53
  54   uint64_t LoopEndCount = CopyLen->getZExtValue() / LoopOpSize;
  55
  56   if (LoopEndCount != 0) {
  57     // Split
  58     PostLoopBB = PreLoopBB->splitBasicBlock(InsertBefore, "memcpy-split");
  59     BasicBlock *LoopBB =
  60         BasicBlock::Create(Ctx, "load-store-loop", ParentFunc, PostLoopBB);
  61     PreLoopBB->getTerminator()->setSuccessor(0, LoopBB);
  62
  63     IRBuilder<> PLBuilder(PreLoopBB->getTerminator());
  64
  65     // Cast the Src and Dst pointers to pointers to the loop operand type (if
  66     // needed).
  67     PointerType *SrcOpType = PointerType::get(LoopOpType, SrcAS);
  68     PointerType *DstOpType = PointerType::get(LoopOpType, DstAS);
  69     if (SrcAddr->getType() != SrcOpType) {
  70       SrcAddr = PLBuilder.CreateBitCast(SrcAddr, SrcOpType);
  71     }
  72     if (DstAddr->getType() != DstOpType) {
  73       DstAddr = PLBuilder.CreateBitCast(DstAddr, DstOpType);
  74     }
  75
  76     Align PartDstAlign(commonAlignment(DstAlign, LoopOpSize));
  77     Align PartSrcAlign(commonAlignment(SrcAlign, LoopOpSize));
  78
  79     IRBuilder<> LoopBuilder(LoopBB);
  80     PHINode *LoopIndex = LoopBuilder.CreatePHI(TypeOfCopyLen, 2, "loop-index");
  81     LoopIndex->addIncoming(ConstantInt::get(TypeOfCopyLen, 0U), PreLoopBB);
  82     // Loop Body
  83     Value *SrcGEP =
  84         LoopBuilder.CreateInBoundsGEP(LoopOpType, SrcAddr, LoopIndex);
  85     LoadInst *Load = LoopBuilder.CreateAlignedLoad(LoopOpType, SrcGEP,
  86                                                    PartSrcAlign, SrcIsVolatile);
  87     if (!CanOverlap) {
  88       // Set alias scope for loads.
  89       Load->setMetadata(LLVMContext::MD_alias_scope,
  90                         MDNode::get(Ctx, NewScope));
  91     }
  92     Value *DstGEP =
  93         LoopBuilder.CreateInBoundsGEP(LoopOpType, DstAddr, LoopIndex);
  94     StoreInst *Store = LoopBuilder.CreateAlignedStore(
  95         Load, DstGEP, PartDstAlign, DstIsVolatile);
  96     if (!CanOverlap) {
  97       // Indicate that stores don't overlap loads.
  98       Store->setMetadata(LLVMContext::MD_noalias, MDNode::get(Ctx, NewScope));
  99     }
 100     if (AtomicElementSize) {
 101       Load->setAtomic(AtomicOrdering::Unordered);
 102       Store->setAtomic(AtomicOrdering::Unordered);
 103     }
 104     Value *NewIndex =
 105         LoopBuilder.CreateAdd(LoopIndex, ConstantInt::get(TypeOfCopyLen, 1U));
 106     LoopIndex->addIncoming(NewIndex, LoopBB);
 107
 108     // Create the loop branch condition.
 109     Constant *LoopEndCI = ConstantInt::get(TypeOfCopyLen, LoopEndCount);
 110     LoopBuilder.CreateCondBr(LoopBuilder.CreateICmpULT(NewIndex, LoopEndCI),
 111                              LoopBB, PostLoopBB);
 112   }
 113
 114   uint64_t BytesCopied = LoopEndCount * LoopOpSize;
 115   uint64_t RemainingBytes = CopyLen->getZExtValue() - BytesCopied;
 116   if (RemainingBytes) {
 117     IRBuilder<> RBuilder(PostLoopBB ? PostLoopBB->getFirstNonPHI()
 118                                     : InsertBefore);
 119
 120     SmallVector<Type *, 5> RemainingOps;
 121     TTI.getMemcpyLoopResidualLoweringType(RemainingOps, Ctx, RemainingBytes,
 122                                           SrcAS, DstAS, SrcAlign.value(),
 123                                           DstAlign.value(), AtomicElementSize);
 124
 125     for (auto OpTy : RemainingOps) {
 126       Align PartSrcAlign(commonAlignment(SrcAlign, BytesCopied));
 127       Align PartDstAlign(commonAlignment(DstAlign, BytesCopied));
 128
 129       // Calculate the new index
 130       unsigned OperandSize = DL.getTypeStoreSize(OpTy);
 131       assert(
 132           (!AtomicElementSize || OperandSize % *AtomicElementSize == 0) &&
 133           "Atomic memcpy lowering is not supported for selected operand size");
 134
 135       uint64_t GepIndex = BytesCopied / OperandSize;
 136       assert(GepIndex * OperandSize == BytesCopied &&
 137              "Division should have no Remainder!");
 138       // Cast source to operand type and load
 139       PointerType *SrcPtrType = PointerType::get(OpTy, SrcAS);
 140       Value *CastedSrc = SrcAddr->getType() == SrcPtrType
 141                              ? SrcAddr
 142                              : RBuilder.CreateBitCast(SrcAddr, SrcPtrType);
 143       Value *SrcGEP = RBuilder.CreateInBoundsGEP(
 144           OpTy, CastedSrc, ConstantInt::get(TypeOfCopyLen, GepIndex));
 145       LoadInst *Load =
 146           RBuilder.CreateAlignedLoad(OpTy, SrcGEP, PartSrcAlign, SrcIsVolatile);
 147       if (!CanOverlap) {
 148         // Set alias scope for loads.
 149         Load->setMetadata(LLVMContext::MD_alias_scope,
 150                           MDNode::get(Ctx, NewScope));
 151       }
 152       // Cast destination to operand type and store.
 153       PointerType *DstPtrType = PointerType::get(OpTy, DstAS);
 154       Value *CastedDst = DstAddr->getType() == DstPtrType
 155                              ? DstAddr
 156                              : RBuilder.CreateBitCast(DstAddr, DstPtrType);
 157       Value *DstGEP = RBuilder.CreateInBoundsGEP(
 158           OpTy, CastedDst, ConstantInt::get(TypeOfCopyLen, GepIndex));
 159       StoreInst *Store = RBuilder.CreateAlignedStore(Load, DstGEP, PartDstAlign,
 160                                                      DstIsVolatile);
 161       if (!CanOverlap) {
 162         // Indicate that stores don't overlap loads.
 163         Store->setMetadata(LLVMContext::MD_noalias, MDNode::get(Ctx, NewScope));
 164       }
 165       if (AtomicElementSize) {
 166         Load->setAtomic(AtomicOrdering::Unordered);
 167         Store->setAtomic(AtomicOrdering::Unordered);
 168       }
 169       BytesCopied += OperandSize;
 170     }
 171   }
 172   assert(BytesCopied == CopyLen->getZExtValue() &&
 173          "Bytes copied should match size in the call!");
 174 }
 175
 176 void llvm::createMemCpyLoopUnknownSize(Instruction *InsertBefore,
 177                                        Value *SrcAddr, Value *DstAddr,
 178                                        Value *CopyLen, Align SrcAlign,
 179                                        Align DstAlign, bool SrcIsVolatile,
 180                                        bool DstIsVolatile, bool CanOverlap,
 181                                        const TargetTransformInfo &TTI,
 182                                        Optional<uint32_t> AtomicElementSize) {
 183   BasicBlock *PreLoopBB = InsertBefore->getParent();
 184   BasicBlock *PostLoopBB =
 185       PreLoopBB->splitBasicBlock(InsertBefore, "post-loop-memcpy-expansion");
 186
 187   Function *ParentFunc = PreLoopBB->getParent();
 188   const DataLayout &DL = ParentFunc->getParent()->getDataLayout();
 189   LLVMContext &Ctx = PreLoopBB->getContext();
 190   MDBuilder MDB(Ctx);
 191   MDNode *NewDomain = MDB.createAnonymousAliasScopeDomain("MemCopyDomain");
 192   StringRef Name = "MemCopyAliasScope";
 193   MDNode *NewScope = MDB.createAnonymousAliasScope(NewDomain, Name);
 194
 195   unsigned SrcAS = cast<PointerType>(SrcAddr->getType())->getAddressSpace();
 196   unsigned DstAS = cast<PointerType>(DstAddr->getType())->getAddressSpace();
 197
 198   Type *LoopOpType = TTI.getMemcpyLoopLoweringType(
 199       Ctx, CopyLen, SrcAS, DstAS, SrcAlign.value(), DstAlign.value(),
 200       AtomicElementSize);
 201   assert((!AtomicElementSize || !LoopOpType->isVectorTy()) &&
 202          "Atomic memcpy lowering is not supported for vector operand type");
 203   unsigned LoopOpSize = DL.getTypeStoreSize(LoopOpType);
 204   assert((!AtomicElementSize || LoopOpSize % *AtomicElementSize == 0) &&
 205          "Atomic memcpy lowering is not supported for selected operand size");
 206
 207   IRBuilder<> PLBuilder(PreLoopBB->getTerminator());
 208
 209   PointerType *SrcOpType = PointerType::get(LoopOpType, SrcAS);
 210   PointerType *DstOpType = PointerType::get(LoopOpType, DstAS);
 211   if (SrcAddr->getType() != SrcOpType) {
 212     SrcAddr = PLBuilder.CreateBitCast(SrcAddr, SrcOpType);
 213   }
 214   if (DstAddr->getType() != DstOpType) {
 215     DstAddr = PLBuilder.CreateBitCast(DstAddr, DstOpType);
 216   }
 217
 218   // Calculate the loop trip count, and remaining bytes to copy after the loop.
 219   Type *CopyLenType = CopyLen->getType();
 220   IntegerType *ILengthType = dyn_cast<IntegerType>(CopyLenType);
 221   assert(ILengthType &&
 222          "expected size argument to memcpy to be an integer type!");
 223   Type *Int8Type = Type::getInt8Ty(Ctx);
 224   bool LoopOpIsInt8 = LoopOpType == Int8Type;
 225   ConstantInt *CILoopOpSize = ConstantInt::get(ILengthType, LoopOpSize);
 226   Value *RuntimeLoopCount = LoopOpIsInt8 ?
 227                             CopyLen :
 228                             PLBuilder.CreateUDiv(CopyLen, CILoopOpSize);
 229   BasicBlock *LoopBB =
 230       BasicBlock::Create(Ctx, "loop-memcpy-expansion", ParentFunc, PostLoopBB);
 231   IRBuilder<> LoopBuilder(LoopBB);
 232
 233   Align PartSrcAlign(commonAlignment(SrcAlign, LoopOpSize));
 234   Align PartDstAlign(commonAlignment(DstAlign, LoopOpSize));
 235
 236   PHINode *LoopIndex = LoopBuilder.CreatePHI(CopyLenType, 2, "loop-index");
 237   LoopIndex->addIncoming(ConstantInt::get(CopyLenType, 0U), PreLoopBB);
 238
 239   Value *SrcGEP = LoopBuilder.CreateInBoundsGEP(LoopOpType, SrcAddr, LoopIndex);
 240   LoadInst *Load = LoopBuilder.CreateAlignedLoad(LoopOpType, SrcGEP,
 241                                                  PartSrcAlign, SrcIsVolatile);
 242   if (!CanOverlap) {
 243     // Set alias scope for loads.
 244     Load->setMetadata(LLVMContext::MD_alias_scope, MDNode::get(Ctx, NewScope));
 245   }
 246   Value *DstGEP = LoopBuilder.CreateInBoundsGEP(LoopOpType, DstAddr, LoopIndex);
 247   StoreInst *Store =
 248       LoopBuilder.CreateAlignedStore(Load, DstGEP, PartDstAlign, DstIsVolatile);
 249   if (!CanOverlap) {
 250     // Indicate that stores don't overlap loads.
 251     Store->setMetadata(LLVMContext::MD_noalias, MDNode::get(Ctx, NewScope));
 252   }
 253   if (AtomicElementSize) {
 254     Load->setAtomic(AtomicOrdering::Unordered);
 255     Store->setAtomic(AtomicOrdering::Unordered);
 256   }
 257   Value *NewIndex =
 258       LoopBuilder.CreateAdd(LoopIndex, ConstantInt::get(CopyLenType, 1U));
 259   LoopIndex->addIncoming(NewIndex, LoopBB);
 260
 261   bool requiresResidual =
 262       !LoopOpIsInt8 && !(AtomicElementSize && LoopOpSize == AtomicElementSize);
 263   if (requiresResidual) {
 264     Type *ResLoopOpType = AtomicElementSize
 265                               ? Type::getIntNTy(Ctx, *AtomicElementSize * 8)
 266                               : Int8Type;
 267     unsigned ResLoopOpSize = DL.getTypeStoreSize(ResLoopOpType);
 268     assert((ResLoopOpSize == AtomicElementSize ? *AtomicElementSize : 1) &&
 269            "Store size is expected to match type size");
 270
 271     // Add in the
 272     Value *RuntimeResidual = PLBuilder.CreateURem(CopyLen, CILoopOpSize);
 273     Value *RuntimeBytesCopied = PLBuilder.CreateSub(CopyLen, RuntimeResidual);
 274
 275     // Loop body for the residual copy.
 276     BasicBlock *ResLoopBB = BasicBlock::Create(Ctx, "loop-memcpy-residual",
 277                                                PreLoopBB->getParent(),
 278                                                PostLoopBB);
 279     // Residual loop header.
 280     BasicBlock *ResHeaderBB = BasicBlock::Create(
 281         Ctx, "loop-memcpy-residual-header", PreLoopBB->getParent(), nullptr);
 282
 283     // Need to update the pre-loop basic block to branch to the correct place.
 284     // branch to the main loop if the count is non-zero, branch to the residual
 285     // loop if the copy size is smaller then 1 iteration of the main loop but
 286     // non-zero and finally branch to after the residual loop if the memcpy
 287     //  size is zero.
 288     ConstantInt *Zero = ConstantInt::get(ILengthType, 0U);
 289     PLBuilder.CreateCondBr(PLBuilder.CreateICmpNE(RuntimeLoopCount, Zero),
 290                            LoopBB, ResHeaderBB);
 291     PreLoopBB->getTerminator()->eraseFromParent();
 292
 293     LoopBuilder.CreateCondBr(
 294         LoopBuilder.CreateICmpULT(NewIndex, RuntimeLoopCount), LoopBB,
 295         ResHeaderBB);
 296
 297     // Determine if we need to branch to the residual loop or bypass it.
 298     IRBuilder<> RHBuilder(ResHeaderBB);
 299     RHBuilder.CreateCondBr(RHBuilder.CreateICmpNE(RuntimeResidual, Zero),
 300                            ResLoopBB, PostLoopBB);
 301
 302     // Copy the residual with single byte load/store loop.
 303     IRBuilder<> ResBuilder(ResLoopBB);
 304     PHINode *ResidualIndex =
 305         ResBuilder.CreatePHI(CopyLenType, 2, "residual-loop-index");
 306     ResidualIndex->addIncoming(Zero, ResHeaderBB);
 307
 308     Value *SrcAsResLoopOpType = ResBuilder.CreateBitCast(
 309         SrcAddr, PointerType::get(ResLoopOpType, SrcAS));
 310     Value *DstAsResLoopOpType = ResBuilder.CreateBitCast(
 311         DstAddr, PointerType::get(ResLoopOpType, DstAS));
 312     Value *FullOffset = ResBuilder.CreateAdd(RuntimeBytesCopied, ResidualIndex);
 313     Value *SrcGEP = ResBuilder.CreateInBoundsGEP(
 314         ResLoopOpType, SrcAsResLoopOpType, FullOffset);
 315     LoadInst *Load = ResBuilder.CreateAlignedLoad(ResLoopOpType, SrcGEP,
 316                                                   PartSrcAlign, SrcIsVolatile);
 317     if (!CanOverlap) {
 318       // Set alias scope for loads.
 319       Load->setMetadata(LLVMContext::MD_alias_scope,
 320                         MDNode::get(Ctx, NewScope));
 321     }
 322     Value *DstGEP = ResBuilder.CreateInBoundsGEP(
 323         ResLoopOpType, DstAsResLoopOpType, FullOffset);
 324     StoreInst *Store = ResBuilder.CreateAlignedStore(Load, DstGEP, PartDstAlign,
 325                                                      DstIsVolatile);
 326     if (!CanOverlap) {
 327       // Indicate that stores don't overlap loads.
 328       Store->setMetadata(LLVMContext::MD_noalias, MDNode::get(Ctx, NewScope));
 329     }
 330     if (AtomicElementSize) {
 331       Load->setAtomic(AtomicOrdering::Unordered);
 332       Store->setAtomic(AtomicOrdering::Unordered);
 333     }
 334     Value *ResNewIndex = ResBuilder.CreateAdd(
 335         ResidualIndex, ConstantInt::get(CopyLenType, ResLoopOpSize));
 336     ResidualIndex->addIncoming(ResNewIndex, ResLoopBB);
 337
 338     // Create the loop branch condition.
 339     ResBuilder.CreateCondBr(
 340         ResBuilder.CreateICmpULT(ResNewIndex, RuntimeResidual), ResLoopBB,
 341         PostLoopBB);
 342   } else {
 343     // In this case the loop operand type was a byte, and there is no need for a
 344     // residual loop to copy the remaining memory after the main loop.
 345     // We do however need to patch up the control flow by creating the
 346     // terminators for the preloop block and the memcpy loop.
 347     ConstantInt *Zero = ConstantInt::get(ILengthType, 0U);
 348     PLBuilder.CreateCondBr(PLBuilder.CreateICmpNE(RuntimeLoopCount, Zero),
 349                            LoopBB, PostLoopBB);
 350     PreLoopBB->getTerminator()->eraseFromParent();
 351     LoopBuilder.CreateCondBr(
 352         LoopBuilder.CreateICmpULT(NewIndex, RuntimeLoopCount), LoopBB,
 353         PostLoopBB);
 354   }
 355 }
 356
 357 // Lower memmove to IR. memmove is required to correctly copy overlapping memory
 358 // regions; therefore, it has to check the relative positions of the source and
 359 // destination pointers and choose the copy direction accordingly.
 360 //
 361 // The code below is an IR rendition of this C function:
 362 //
 363 // void* memmove(void* dst, const void* src, size_t n) {
 364 //   unsigned char* d = dst;
 365 //   const unsigned char* s = src;
 366 //   if (s < d) {
 367 //     // copy backwards
 368 //     while (n--) {
 369 //       d[n] = s[n];
 370 //     }
 371 //   } else {
 372 //     // copy forward
 373 //     for (size_t i = 0; i < n; ++i) {
 374 //       d[i] = s[i];
 375 //     }
 376 //   }
 377 //   return dst;
 378 // }
 379 static void createMemMoveLoop(Instruction *InsertBefore, Value *SrcAddr,
 380                               Value *DstAddr, Value *CopyLen, Align SrcAlign,
 381                               Align DstAlign, bool SrcIsVolatile,
 382                               bool DstIsVolatile) {
 383   Type *TypeOfCopyLen = CopyLen->getType();
 384   BasicBlock *OrigBB = InsertBefore->getParent();
 385   Function *F = OrigBB->getParent();
 386   const DataLayout &DL = F->getParent()->getDataLayout();
 387
 388   // TODO: Use different element type if possible?
 389   IRBuilder<> CastBuilder(InsertBefore);
 390   Type *EltTy = CastBuilder.getInt8Ty();
 391   Type *PtrTy =
 392       CastBuilder.getInt8PtrTy(SrcAddr->getType()->getPointerAddressSpace());
 393   SrcAddr = CastBuilder.CreateBitCast(SrcAddr, PtrTy);
 394   DstAddr = CastBuilder.CreateBitCast(DstAddr, PtrTy);
 395
 396   // Create the a comparison of src and dst, based on which we jump to either
 397   // the forward-copy part of the function (if src >= dst) or the backwards-copy
 398   // part (if src < dst).
 399   // SplitBlockAndInsertIfThenElse conveniently creates the basic if-then-else
 400   // structure. Its block terminators (unconditional branches) are replaced by
 401   // the appropriate conditional branches when the loop is built.
 402   ICmpInst *PtrCompare = new ICmpInst(InsertBefore, ICmpInst::ICMP_ULT,
 403                                       SrcAddr, DstAddr, "compare_src_dst");
 404   Instruction *ThenTerm, *ElseTerm;
 405   SplitBlockAndInsertIfThenElse(PtrCompare, InsertBefore, &ThenTerm,
 406                                 &ElseTerm);
 407
 408   // Each part of the function consists of two blocks:
 409   //   copy_backwards:        used to skip the loop when n == 0
 410   //   copy_backwards_loop:   the actual backwards loop BB
 411   //   copy_forward:          used to skip the loop when n == 0
 412   //   copy_forward_loop:     the actual forward loop BB
 413   BasicBlock *CopyBackwardsBB = ThenTerm->getParent();
 414   CopyBackwardsBB->setName("copy_backwards");
 415   BasicBlock *CopyForwardBB = ElseTerm->getParent();
 416   CopyForwardBB->setName("copy_forward");
 417   BasicBlock *ExitBB = InsertBefore->getParent();
 418   ExitBB->setName("memmove_done");
 419
 420   unsigned PartSize = DL.getTypeStoreSize(EltTy);
 421   Align PartSrcAlign(commonAlignment(SrcAlign, PartSize));
 422   Align PartDstAlign(commonAlignment(DstAlign, PartSize));
 423
 424   // Initial comparison of n == 0 that lets us skip the loops altogether. Shared
 425   // between both backwards and forward copy clauses.
 426   ICmpInst *CompareN =
 427       new ICmpInst(OrigBB->getTerminator(), ICmpInst::ICMP_EQ, CopyLen,
 428                    ConstantInt::get(TypeOfCopyLen, 0), "compare_n_to_0");
 429
 430   // Copying backwards.
 431   BasicBlock *LoopBB =
 432     BasicBlock::Create(F->getContext(), "copy_backwards_loop", F, CopyForwardBB);
 433   IRBuilder<> LoopBuilder(LoopBB);
 434   PHINode *LoopPhi = LoopBuilder.CreatePHI(TypeOfCopyLen, 0);
 435   Value *IndexPtr = LoopBuilder.CreateSub(
 436       LoopPhi, ConstantInt::get(TypeOfCopyLen, 1), "index_ptr");
 437   Value *Element = LoopBuilder.CreateAlignedLoad(
 438       EltTy, LoopBuilder.CreateInBoundsGEP(EltTy, SrcAddr, IndexPtr),
 439       PartSrcAlign, "element");
 440   LoopBuilder.CreateAlignedStore(
 441       Element, LoopBuilder.CreateInBoundsGEP(EltTy, DstAddr, IndexPtr),
 442       PartDstAlign);
 443   LoopBuilder.CreateCondBr(
 444       LoopBuilder.CreateICmpEQ(IndexPtr, ConstantInt::get(TypeOfCopyLen, 0)),
 445       ExitBB, LoopBB);
 446   LoopPhi->addIncoming(IndexPtr, LoopBB);
 447   LoopPhi->addIncoming(CopyLen, CopyBackwardsBB);
 448   BranchInst::Create(ExitBB, LoopBB, CompareN, ThenTerm);
 449   ThenTerm->eraseFromParent();
 450
 451   // Copying forward.
 452   BasicBlock *FwdLoopBB =
 453     BasicBlock::Create(F->getContext(), "copy_forward_loop", F, ExitBB);
 454   IRBuilder<> FwdLoopBuilder(FwdLoopBB);
 455   PHINode *FwdCopyPhi = FwdLoopBuilder.CreatePHI(TypeOfCopyLen, 0, "index_ptr");
 456   Value *SrcGEP = FwdLoopBuilder.CreateInBoundsGEP(EltTy, SrcAddr, FwdCopyPhi);
 457   Value *FwdElement =
 458       FwdLoopBuilder.CreateAlignedLoad(EltTy, SrcGEP, PartSrcAlign, "element");
 459   Value *DstGEP = FwdLoopBuilder.CreateInBoundsGEP(EltTy, DstAddr, FwdCopyPhi);
 460   FwdLoopBuilder.CreateAlignedStore(FwdElement, DstGEP, PartDstAlign);
 461   Value *FwdIndexPtr = FwdLoopBuilder.CreateAdd(
 462       FwdCopyPhi, ConstantInt::get(TypeOfCopyLen, 1), "index_increment");
 463   FwdLoopBuilder.CreateCondBr(FwdLoopBuilder.CreateICmpEQ(FwdIndexPtr, CopyLen),
 464                               ExitBB, FwdLoopBB);
 465   FwdCopyPhi->addIncoming(FwdIndexPtr, FwdLoopBB);
 466   FwdCopyPhi->addIncoming(ConstantInt::get(TypeOfCopyLen, 0), CopyForwardBB);
 467
 468   BranchInst::Create(ExitBB, FwdLoopBB, CompareN, ElseTerm);
 469   ElseTerm->eraseFromParent();
 470 }
 471
 472 static void createMemSetLoop(Instruction *InsertBefore, Value *DstAddr,
 473                              Value *CopyLen, Value *SetValue, Align DstAlign,
 474                              bool IsVolatile) {
 475   Type *TypeOfCopyLen = CopyLen->getType();
 476   BasicBlock *OrigBB = InsertBefore->getParent();
 477   Function *F = OrigBB->getParent();
 478   const DataLayout &DL = F->getParent()->getDataLayout();
 479   BasicBlock *NewBB =
 480       OrigBB->splitBasicBlock(InsertBefore, "split");
 481   BasicBlock *LoopBB
 482     = BasicBlock::Create(F->getContext(), "loadstoreloop", F, NewBB);
 483
 484   IRBuilder<> Builder(OrigBB->getTerminator());
 485
 486   // Cast pointer to the type of value getting stored
 487   unsigned dstAS = cast<PointerType>(DstAddr->getType())->getAddressSpace();
 488   DstAddr = Builder.CreateBitCast(DstAddr,
 489                                   PointerType::get(SetValue->getType(), dstAS));
 490
 491   Builder.CreateCondBr(
 492       Builder.CreateICmpEQ(ConstantInt::get(TypeOfCopyLen, 0), CopyLen), NewBB,
 493       LoopBB);
 494   OrigBB->getTerminator()->eraseFromParent();
 495
 496   unsigned PartSize = DL.getTypeStoreSize(SetValue->getType());
 497   Align PartAlign(commonAlignment(DstAlign, PartSize));
 498
 499   IRBuilder<> LoopBuilder(LoopBB);
 500   PHINode *LoopIndex = LoopBuilder.CreatePHI(TypeOfCopyLen, 0);
 501   LoopIndex->addIncoming(ConstantInt::get(TypeOfCopyLen, 0), OrigBB);
 502
 503   LoopBuilder.CreateAlignedStore(
 504       SetValue,
 505       LoopBuilder.CreateInBoundsGEP(SetValue->getType(), DstAddr, LoopIndex),
 506       PartAlign, IsVolatile);
 507
 508   Value *NewIndex =
 509       LoopBuilder.CreateAdd(LoopIndex, ConstantInt::get(TypeOfCopyLen, 1));
 510   LoopIndex->addIncoming(NewIndex, LoopBB);
 511
 512   LoopBuilder.CreateCondBr(LoopBuilder.CreateICmpULT(NewIndex, CopyLen), LoopBB,
 513                            NewBB);
 514 }
 515
 516 template <typename T>
 517 static bool canOverlap(MemTransferBase<T> *Memcpy, ScalarEvolution *SE) {
 518   if (SE) {
 519     auto *SrcSCEV = SE->getSCEV(Memcpy->getRawSource());
 520     auto *DestSCEV = SE->getSCEV(Memcpy->getRawDest());
 521     if (SE->isKnownPredicateAt(CmpInst::ICMP_NE, SrcSCEV, DestSCEV, Memcpy))
 522       return false;
 523   }
 524   return true;
 525 }
 526
 527 void llvm::expandMemCpyAsLoop(MemCpyInst *Memcpy,
 528                               const TargetTransformInfo &TTI,
 529                               ScalarEvolution *SE) {
 530   bool CanOverlap = canOverlap(Memcpy, SE);
 531   if (ConstantInt *CI = dyn_cast<ConstantInt>(Memcpy->getLength())) {
 532     createMemCpyLoopKnownSize(
 533         /* InsertBefore */ Memcpy,
 534         /* SrcAddr */ Memcpy->getRawSource(),
 535         /* DstAddr */ Memcpy->getRawDest(),
 536         /* CopyLen */ CI,
 537         /* SrcAlign */ Memcpy->getSourceAlign().valueOrOne(),
 538         /* DestAlign */ Memcpy->getDestAlign().valueOrOne(),
 539         /* SrcIsVolatile */ Memcpy->isVolatile(),
 540         /* DstIsVolatile */ Memcpy->isVolatile(),
 541         /* CanOverlap */ CanOverlap,
 542         /* TargetTransformInfo */ TTI);
 543   } else {
 544     createMemCpyLoopUnknownSize(
 545         /* InsertBefore */ Memcpy,
 546         /* SrcAddr */ Memcpy->getRawSource(),
 547         /* DstAddr */ Memcpy->getRawDest(),
 548         /* CopyLen */ Memcpy->getLength(),
 549         /* SrcAlign */ Memcpy->getSourceAlign().valueOrOne(),
 550         /* DestAlign */ Memcpy->getDestAlign().valueOrOne(),
 551         /* SrcIsVolatile */ Memcpy->isVolatile(),
 552         /* DstIsVolatile */ Memcpy->isVolatile(),
 553         /* CanOverlap */ CanOverlap,
 554         /* TargetTransformInfo */ TTI);
 555   }
 556 }
 557
 558 void llvm::expandMemMoveAsLoop(MemMoveInst *Memmove) {
 559   createMemMoveLoop(/* InsertBefore */ Memmove,
 560                     /* SrcAddr */ Memmove->getRawSource(),
 561                     /* DstAddr */ Memmove->getRawDest(),
 562                     /* CopyLen */ Memmove->getLength(),
 563                     /* SrcAlign */ Memmove->getSourceAlign().valueOrOne(),
 564                     /* DestAlign */ Memmove->getDestAlign().valueOrOne(),
 565                     /* SrcIsVolatile */ Memmove->isVolatile(),
 566                     /* DstIsVolatile */ Memmove->isVolatile());
 567 }
 568
 569 void llvm::expandMemSetAsLoop(MemSetInst *Memset) {
 570   createMemSetLoop(/* InsertBefore */ Memset,
 571                    /* DstAddr */ Memset->getRawDest(),
 572                    /* CopyLen */ Memset->getLength(),
 573                    /* SetValue */ Memset->getValue(),
 574                    /* Alignment */ Memset->getDestAlign().valueOrOne(),
 575                    Memset->isVolatile());
 576 }
 577
 578 void llvm::expandAtomicMemCpyAsLoop(AtomicMemCpyInst *AtomicMemcpy,
 579                                     const TargetTransformInfo &TTI,
 580                                     ScalarEvolution *SE) {
 581   if (ConstantInt *CI = dyn_cast<ConstantInt>(AtomicMemcpy->getLength())) {
 582     createMemCpyLoopKnownSize(
 583         /* InsertBefore */ AtomicMemcpy,
 584         /* SrcAddr */ AtomicMemcpy->getRawSource(),
 585         /* DstAddr */ AtomicMemcpy->getRawDest(),
 586         /* CopyLen */ CI,
 587         /* SrcAlign */ AtomicMemcpy->getSourceAlign().valueOrOne(),
 588         /* DestAlign */ AtomicMemcpy->getDestAlign().valueOrOne(),
 589         /* SrcIsVolatile */ AtomicMemcpy->isVolatile(),
 590         /* DstIsVolatile */ AtomicMemcpy->isVolatile(),
 591         /* CanOverlap */ false, // SrcAddr & DstAddr may not overlap by spec.
 592         /* TargetTransformInfo */ TTI,
 593         /* AtomicCpySize */ AtomicMemcpy->getElementSizeInBytes());
 594   } else {
 595     createMemCpyLoopUnknownSize(
 596         /* InsertBefore */ AtomicMemcpy,
 597         /* SrcAddr */ AtomicMemcpy->getRawSource(),
 598         /* DstAddr */ AtomicMemcpy->getRawDest(),
 599         /* CopyLen */ AtomicMemcpy->getLength(),
 600         /* SrcAlign */ AtomicMemcpy->getSourceAlign().valueOrOne(),
 601         /* DestAlign */ AtomicMemcpy->getDestAlign().valueOrOne(),
 602         /* SrcIsVolatile */ AtomicMemcpy->isVolatile(),
 603         /* DstIsVolatile */ AtomicMemcpy->isVolatile(),
 604         /* CanOverlap */ false, // SrcAddr & DstAddr may not overlap by spec.
 605         /* TargetTransformInfo */ TTI,
 606         /* AtomicCpySize */ AtomicMemcpy->getElementSizeInBytes());
 607   }
 608 }