Revert "[llvm][ARM]Add widen global arrays pass" (#112701)

Reverts #107120 

Unexpected build failures in post-commit pipelines. Needs investigation

Author: nasherm

llvm/include/llvm/Analysis/TargetTransformInfo.h

@@ -1819,10 +1819,6 @@ class TargetTransformInfo {
   /// \return The maximum number of function arguments the target supports.
   unsigned getMaxNumArgs() const;
 
-  /// \return For an array of given Size, return alignment boundary to
-  /// pad to. Default is no padding.
-  unsigned getNumBytesToPadGlobalArray(unsigned Size, Type *ArrayType) const;
-
   /// @}
 
 private:
@@ -2229,8 +2225,6 @@ class TargetTransformInfo::Concept {
   getVPLegalizationStrategy(const VPIntrinsic &PI) const = 0;
   virtual bool hasArmWideBranch(bool Thumb) const = 0;
   virtual unsigned getMaxNumArgs() const = 0;
-  virtual unsigned getNumBytesToPadGlobalArray(unsigned Size,
-                                               Type *ArrayType) const = 0;
 };
 
 template <typename T>
@@ -3032,11 +3026,6 @@ class TargetTransformInfo::Model final : public TargetTransformInfo::Concept {
   unsigned getMaxNumArgs() const override {
     return Impl.getMaxNumArgs();
   }
-
-  unsigned getNumBytesToPadGlobalArray(unsigned Size,
-                                       Type *ArrayType) const override {
-    return Impl.getNumBytesToPadGlobalArray(Size, ArrayType);
-  }
 };
 
 template <typename T>

llvm/include/llvm/Analysis/TargetTransformInfoImpl.h

@@ -1006,10 +1006,6 @@ class TargetTransformInfoImplBase {
 
   unsigned getMaxNumArgs() const { return UINT_MAX; }
 
-  unsigned getNumBytesToPadGlobalArray(unsigned Size, Type *ArrayType) const {
-    return 0;
-  }
-
 protected:
   // Obtain the minimum required size to hold the value (without the sign)
   // In case of a vector it returns the min required size for one element.

llvm/lib/Analysis/TargetTransformInfo.cpp

@@ -1383,12 +1383,6 @@ bool TargetTransformInfo::isVectorShiftByScalarCheap(Type *Ty) const {
   return TTIImpl->isVectorShiftByScalarCheap(Ty);
 }
 
-unsigned
-TargetTransformInfo::getNumBytesToPadGlobalArray(unsigned Size,
-                                                 Type *ArrayType) const {
-  return TTIImpl->getNumBytesToPadGlobalArray(Size, ArrayType);
-}
-
 TargetTransformInfo::Concept::~Concept() = default;
 
 TargetIRAnalysis::TargetIRAnalysis() : TTICallback(&getDefaultTTI) {}

llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp

@@ -56,10 +56,6 @@ static cl::opt<bool>
     AllowWLSLoops("allow-arm-wlsloops", cl::Hidden, cl::init(true),
                   cl::desc("Enable the generation of WLS loops"));
 
-static cl::opt<bool> UseWidenGlobalArrays(
-    "widen-global-strings", cl::Hidden, cl::init(true),
-    cl::desc("Enable the widening of global strings to alignment boundaries"));
-
 extern cl::opt<TailPredication::Mode> EnableTailPredication;
 
 extern cl::opt<bool> EnableMaskedGatherScatters;
@@ -2809,32 +2805,3 @@ bool ARMTTIImpl::isProfitableToSinkOperands(Instruction *I,
   }
   return true;
 }
-
-unsigned ARMTTIImpl::getNumBytesToPadGlobalArray(unsigned Size,
-                                                 Type *ArrayType) const {
-  if (!UseWidenGlobalArrays) {
-    LLVM_DEBUG(dbgs() << "Padding global arrays disabled\n");
-    return false;
-  }
-
-  // Don't modify none integer array types
-  if (!ArrayType || !ArrayType->isArrayTy() ||
-      !ArrayType->getArrayElementType()->isIntegerTy())
-    return 0;
-
-  // We pad to 4 byte boundaries
-  if (Size % 4 == 0)
-    return 0;
-
-  unsigned NumBytesToPad = 4 - (Size % 4);
-  unsigned NewSize = Size + NumBytesToPad;
-
-  // Max number of bytes that memcpy allows for lowering to load/stores before
-  // it uses library function (__aeabi_memcpy).
-  unsigned MaxMemIntrinsicSize = getMaxMemIntrinsicInlineSizeThreshold();
-
-  if (NewSize > MaxMemIntrinsicSize)
-    return 0;
-
-  return NumBytesToPad;
-}

llvm/lib/Target/ARM/ARMTargetTransformInfo.h

@@ -337,9 +337,6 @@ class ARMTTIImpl : public BasicTTIImplBase<ARMTTIImpl> {
 
   bool isProfitableToSinkOperands(Instruction *I,
                                   SmallVectorImpl<Use *> &Ops) const;
-
-  unsigned getNumBytesToPadGlobalArray(unsigned Size, Type *ArrayType) const;
-
   /// @}
 };
 

llvm/lib/Transforms/IPO/GlobalOpt.cpp

@@ -92,8 +92,6 @@ STATISTIC(NumInternalFunc, "Number of internal functions");
 STATISTIC(NumColdCC, "Number of functions marked coldcc");
 STATISTIC(NumIFuncsResolved, "Number of statically resolved IFuncs");
 STATISTIC(NumIFuncsDeleted, "Number of IFuncs removed");
-STATISTIC(NumGlobalArraysPadded,
-          "Number of global arrays padded to alignment boundary");
 
 static cl::opt<bool>
     EnableColdCCStressTest("enable-coldcc-stress-test",
@@ -2031,165 +2029,6 @@ OptimizeFunctions(Module &M,
   return Changed;
 }
 
-static bool callInstIsMemcpy(CallInst *CI) {
-  if (!CI)
-    return false;
-
-  Function *F = CI->getCalledFunction();
-  if (!F || !F->isIntrinsic() || F->getIntrinsicID() != Intrinsic::memcpy)
-    return false;
-
-  return true;
-}
-
-static bool destArrayCanBeWidened(CallInst *CI) {
-  auto *IsVolatile = dyn_cast<ConstantInt>(CI->getArgOperand(3));
-  auto *Alloca = dyn_cast<AllocaInst>(CI->getArgOperand(0));
-
-  if (!Alloca || !IsVolatile || IsVolatile->isOne())
-    return false;
-
-  if (!Alloca->isStaticAlloca())
-    return false;
-
-  if (!Alloca->getAllocatedType()->isArrayTy())
-    return false;
-
-  return true;
-}
-
-static GlobalVariable *widenGlobalVariable(GlobalVariable *OldVar, Function *F,
-                                           unsigned NumBytesToPad,
-                                           unsigned NumBytesToCopy) {
-  if (!OldVar->hasInitializer())
-    return nullptr;
-
-  ConstantDataArray *DataArray =
-      dyn_cast<ConstantDataArray>(OldVar->getInitializer());
-  if (!DataArray)
-    return nullptr;
-
-  // Update to be word aligned (memcpy(...,X,...))
-  // create replacement with padded null bytes.
-  StringRef Data = DataArray->getRawDataValues();
-  std::vector<uint8_t> StrData(Data.begin(), Data.end());
-  for (unsigned int p = 0; p < NumBytesToPad; p++)
-    StrData.push_back('\0');
-  auto Arr = ArrayRef(StrData.data(), NumBytesToCopy + NumBytesToPad);
-  // Create new padded version of global variable.
-  Constant *SourceReplace = ConstantDataArray::get(F->getContext(), Arr);
-  GlobalVariable *NewGV = new GlobalVariable(
-      *(F->getParent()), SourceReplace->getType(), true, OldVar->getLinkage(),
-      SourceReplace, SourceReplace->getName());
-  // Copy any other attributes from original global variable
-  // e.g. unamed_addr
-  NewGV->copyAttributesFrom(OldVar);
-  NewGV->takeName(OldVar);
-  return NewGV;
-}
-
-static void widenDestArray(CallInst *CI, const unsigned NumBytesToPad,
-                           const unsigned NumBytesToCopy,
-                           ConstantDataArray *SourceDataArray) {
-
-  auto *Alloca = dyn_cast<AllocaInst>(CI->getArgOperand(0));
-  if (Alloca) {
-    unsigned ElementByteWidth = SourceDataArray->getElementByteSize();
-    unsigned int TotalBytes = NumBytesToCopy + NumBytesToPad;
-    unsigned NumElementsToCopy = divideCeil(TotalBytes, ElementByteWidth);
-    // Update destination array to be word aligned (memcpy(X,...,...))
-    IRBuilder<> BuildAlloca(Alloca);
-    AllocaInst *NewAlloca = BuildAlloca.CreateAlloca(ArrayType::get(
-        Alloca->getAllocatedType()->getArrayElementType(), NumElementsToCopy));
-    NewAlloca->takeName(Alloca);
-    NewAlloca->setAlignment(Alloca->getAlign());
-    Alloca->replaceAllUsesWith(NewAlloca);
-    Alloca->eraseFromParent();
-  }
-}
-
-static bool tryWidenGlobalArrayAndDests(Function *F, GlobalVariable *SourceVar,
-                                        const unsigned NumBytesToPad,
-                                        const unsigned NumBytesToCopy,
-                                        ConstantInt *BytesToCopyOp,
-                                        ConstantDataArray *SourceDataArray) {
-  auto *NewSourceGV =
-      widenGlobalVariable(SourceVar, F, NumBytesToPad, NumBytesToCopy);
-  if (!NewSourceGV)
-    return false;
-
-  // Update arguments of remaining uses  that
-  // are memcpys.
-  for (auto *User : SourceVar->users()) {
-    auto *CI = dyn_cast<CallInst>(User);
-    if (!callInstIsMemcpy(CI) || !destArrayCanBeWidened(CI))
-      continue;
-
-    if (CI->getArgOperand(1) != SourceVar)
-      continue;
-
-    widenDestArray(CI, NumBytesToPad, NumBytesToCopy, SourceDataArray);
-
-    CI->setArgOperand(2, ConstantInt::get(BytesToCopyOp->getType(),
-                                          NumBytesToCopy + NumBytesToPad));
-  }
-  SourceVar->replaceAllUsesWith(NewSourceGV);
-
-  NumGlobalArraysPadded++;
-  return true;
-}
-
-static bool tryWidenGlobalArraysUsedByMemcpy(
-    GlobalVariable *GV,
-    function_ref<TargetTransformInfo &(Function &)> GetTTI) {
-
-  if (!GV->hasInitializer() || !GV->isConstant() || !GV->hasLocalLinkage() ||
-      !GV->hasGlobalUnnamedAddr())
-    return false;
-
-  for (auto *User : GV->users()) {
-    CallInst *CI = dyn_cast<CallInst>(User);
-    if (!callInstIsMemcpy(CI) || !destArrayCanBeWidened(CI))
-      continue;
-
-    Function *F = CI->getCalledFunction();
-
-    auto *BytesToCopyOp = dyn_cast<ConstantInt>(CI->getArgOperand(2));
-    if (!BytesToCopyOp)
-      continue;
-
-    ConstantDataArray *SourceDataArray =
-        dyn_cast<ConstantDataArray>(GV->getInitializer());
-    if (!SourceDataArray)
-      continue;
-
-    unsigned NumBytesToCopy = BytesToCopyOp->getZExtValue();
-
-    auto *Alloca = dyn_cast<AllocaInst>(CI->getArgOperand(0));
-    uint64_t DZSize = Alloca->getAllocatedType()->getArrayNumElements();
-    uint64_t SZSize = SourceDataArray->getType()->getNumElements();
-    unsigned ElementByteWidth = SourceDataArray->getElementByteSize();
-    // Calculate the number of elements to copy while avoiding floored
-    // division of integers returning wrong values i.e. copying one byte
-    // from an array of i16 would yield 0 elements to copy as supposed to 1.
-    unsigned NumElementsToCopy = divideCeil(NumBytesToCopy, ElementByteWidth);
-
-    // For safety purposes lets add a constraint and only pad when
-    // NumElementsToCopy == destination array size ==
-    // source which is a constant
-    if (NumElementsToCopy != DZSize || DZSize != SZSize)
-      continue;
-
-    unsigned NumBytesToPad = GetTTI(*F).getNumBytesToPadGlobalArray(
-        NumBytesToCopy, SourceDataArray->getType());
-    if (NumBytesToPad) {
-      return tryWidenGlobalArrayAndDests(F, GV, NumBytesToPad, NumBytesToCopy,
-                                         BytesToCopyOp, SourceDataArray);
-    }
-  }
-  return false;
-}
-
 static bool
 OptimizeGlobalVars(Module &M,
                    function_ref<TargetTransformInfo &(Function &)> GetTTI,
@@ -2219,10 +2058,6 @@ OptimizeGlobalVars(Module &M,
       continue;
     }
 
-    // For global variable arrays called in a memcpy
-    // we try to pad to nearest valid alignment boundary
-    Changed |= tryWidenGlobalArraysUsedByMemcpy(&GV, GetTTI);
-
     Changed |= processGlobal(GV, GetTTI, GetTLI, LookupDomTree);
   }
   return Changed;