llvm/Analysis/TargetLibraryInfo.h

//===-- TargetLibraryInfo.h - Library information ---------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_ANALYSIS_TARGETLIBRARYINFO_H
#define LLVM_ANALYSIS_TARGETLIBRARYINFO_H

#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/Optional.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/PassManager.h"
#include "llvm/Pass.h"

namespace llvm {
template <typename T> class ArrayRef;
class Triple;

/// Describes a possible vectorization of a function.
/// Function 'VectorFnName' is equivalent to 'ScalarFnName' vectorized
/// by a factor 'VectorizationFactor'.
struct VecDesc {
  StringRef ScalarFnName;
  StringRef VectorFnName;
  unsigned VectorizationFactor;
};

  enum LibFunc : unsigned {
#define TLI_DEFINE_ENUM
#include "llvm/Analysis/TargetLibraryInfo.def"

    NumLibFuncs,
    NotLibFunc
  };

/// Implementation of the target library information.
///
/// This class constructs tables that hold the target library information and
/// make it available. However, it is somewhat expensive to compute and only
/// depends on the triple. So users typically interact with the \c
/// TargetLibraryInfo wrapper below.
class TargetLibraryInfoImpl {
  friend class TargetLibraryInfo;

  unsigned char AvailableArray[(NumLibFuncs+3)/4];
  llvm::DenseMap<unsigned, std::string> CustomNames;
  static StringLiteral const StandardNames[NumLibFuncs];
  bool ShouldExtI32Param, ShouldExtI32Return, ShouldSignExtI32Param;

  enum AvailabilityState {
    StandardName = 3, // (memset to all ones)
    CustomName = 1,
    Unavailable = 0  // (memset to all zeros)
  };
  void setState(LibFunc F, AvailabilityState State) {
    AvailableArray[F/4] &= ~(3 << 2*(F&3));
    AvailableArray[F/4] |= State << 2*(F&3);
  }
  AvailabilityState getState(LibFunc F) const {
    return static_cast<AvailabilityState>((AvailableArray[F/4] >> 2*(F&3)) & 3);
  }

  /// Vectorization descriptors - sorted by ScalarFnName.
  std::vector<VecDesc> VectorDescs;
  /// Scalarization descriptors - same content as VectorDescs but sorted based
  /// on VectorFnName rather than ScalarFnName.
  std::vector<VecDesc> ScalarDescs;

  /// Return true if the function type FTy is valid for the library function
  /// F, regardless of whether the function is available.
  bool isValidProtoForLibFunc(const FunctionType &FTy, LibFunc F,
                              const DataLayout *DL) const;

public:
  /// List of known vector-functions libraries.
  ///
  /// The vector-functions library defines, which functions are vectorizable
  /// and with which factor. The library can be specified by either frontend,
  /// or a commandline option, and then used by
  /// addVectorizableFunctionsFromVecLib for filling up the tables of
  /// vectorizable functions.
  enum VectorLibrary {
    NoLibrary,  // Don't use any vector library.
    Accelerate, // Use Accelerate framework.
    MASSV,      // IBM MASS vector library.
    SVML        // Intel short vector math library.
  };

  TargetLibraryInfoImpl();
  explicit TargetLibraryInfoImpl(const Triple &T);

  // Provide value semantics.
  TargetLibraryInfoImpl(const TargetLibraryInfoImpl &TLI);
  TargetLibraryInfoImpl(TargetLibraryInfoImpl &&TLI);
  TargetLibraryInfoImpl &operator=(const TargetLibraryInfoImpl &TLI);
  TargetLibraryInfoImpl &operator=(TargetLibraryInfoImpl &&TLI);

  /// Searches for a particular function name.
  ///
  /// If it is one of the known library functions, return true and set F to the
  /// corresponding value.
  bool getLibFunc(StringRef funcName, LibFunc &F) const;

  /// Searches for a particular function name, also checking that its type is
  /// valid for the library function matching that name.
  ///
  /// If it is one of the known library functions, return true and set F to the
  /// corresponding value.
  bool getLibFunc(const Function &FDecl, LibFunc &F) const;

  /// Forces a function to be marked as unavailable.
  void setUnavailable(LibFunc F) {
    setState(F, Unavailable);
  }

  /// Forces a function to be marked as available.
  void setAvailable(LibFunc F) {
    setState(F, StandardName);
  }

  /// Forces a function to be marked as available and provide an alternate name
  /// that must be used.
  void setAvailableWithName(LibFunc F, StringRef Name) {
    if (StandardNames[F] != Name) {
      setState(F, CustomName);
      CustomNames[F] = std::string(Name);
      assert(CustomNames.find(F) != CustomNames.end());
    } else {
      setState(F, StandardName);
    }
  }

  /// Disables all builtins.
  ///
  /// This can be used for options like -fno-builtin.
  void disableAllFunctions();

  /// Add a set of scalar -> vector mappings, queryable via
  /// getVectorizedFunction and getScalarizedFunction.
  void addVectorizableFunctions(ArrayRef<VecDesc> Fns);

  /// Calls addVectorizableFunctions with a known preset of functions for the
  /// given vector library.
  void addVectorizableFunctionsFromVecLib(enum VectorLibrary VecLib);

  /// Return true if the function F has a vector equivalent with vectorization
  /// factor VF.
  bool isFunctionVectorizable(StringRef F, unsigned VF) const {
    return !getVectorizedFunction(F, VF).empty();
  }

  /// Return true if the function F has a vector equivalent with any
  /// vectorization factor.
  bool isFunctionVectorizable(StringRef F) const;

  /// Return the name of the equivalent of F, vectorized with factor VF. If no
  /// such mapping exists, return the empty string.
  StringRef getVectorizedFunction(StringRef F, unsigned VF) const;

  /// Return true if the function F has a scalar equivalent, and set VF to be
  /// the vectorization factor.
  bool isFunctionScalarizable(StringRef F, unsigned &VF) const {
    return !getScalarizedFunction(F, VF).empty();
  }

  /// Return the name of the equivalent of F, scalarized. If no such mapping
  /// exists, return the empty string.
  ///
  /// Set VF to the vectorization factor.
  StringRef getScalarizedFunction(StringRef F, unsigned &VF) const;

  /// Set to true iff i32 parameters to library functions should have signext
  /// or zeroext attributes if they correspond to C-level int or unsigned int,
  /// respectively.
  void setShouldExtI32Param(bool Val) {
    ShouldExtI32Param = Val;
  }

  /// Set to true iff i32 results from library functions should have signext
  /// or zeroext attributes if they correspond to C-level int or unsigned int,
  /// respectively.
  void setShouldExtI32Return(bool Val) {
    ShouldExtI32Return = Val;
  }

  /// Set to true iff i32 parameters to library functions should have signext
  /// attribute if they correspond to C-level int or unsigned int.
  void setShouldSignExtI32Param(bool Val) {
    ShouldSignExtI32Param = Val;
  }

  /// Returns the size of the wchar_t type in bytes or 0 if the size is unknown.
  /// This queries the 'wchar_size' metadata.
  unsigned getWCharSize(const Module &M) const;

  /// Returns the largest vectorization factor used in the list of
  /// vector functions.
  unsigned getWidestVF(StringRef ScalarF) const;
};

/// Provides information about what library functions are available for
/// the current target.
///
/// This both allows optimizations to handle them specially and frontends to
/// disable such optimizations through -fno-builtin etc.
class TargetLibraryInfo {
  friend class TargetLibraryAnalysis;
  friend class TargetLibraryInfoWrapperPass;

  /// The global (module level) TLI info.
  const TargetLibraryInfoImpl *Impl;

  /// Support for -fno-builtin* options as function attributes, overrides
  /// information in global TargetLibraryInfoImpl.
  BitVector OverrideAsUnavailable;

public:
  explicit TargetLibraryInfo(const TargetLibraryInfoImpl &Impl,
                             Optional<const Function *> F = None)
      : Impl(&Impl), OverrideAsUnavailable(NumLibFuncs) {
    if (!F)
      return;
    if ((*F)->hasFnAttribute("no-builtins"))
      disableAllFunctions();
    else {
      // Disable individual libc/libm calls in TargetLibraryInfo.
      LibFunc LF;
      AttributeSet FnAttrs = (*F)->getAttributes().getFnAttributes();
      for (const Attribute &Attr : FnAttrs) {
        if (!Attr.isStringAttribute())
          continue;
        auto AttrStr = Attr.getKindAsString();
        if (!AttrStr.consume_front("no-builtin-"))
          continue;
        if (getLibFunc(AttrStr, LF))
          setUnavailable(LF);
      }
    }
  }

  // Provide value semantics.
  TargetLibraryInfo(const TargetLibraryInfo &TLI)
      : Impl(TLI.Impl), OverrideAsUnavailable(TLI.OverrideAsUnavailable) {}
  TargetLibraryInfo(TargetLibraryInfo &&TLI)
      : Impl(TLI.Impl), OverrideAsUnavailable(TLI.OverrideAsUnavailable) {}
  TargetLibraryInfo &operator=(const TargetLibraryInfo &TLI) {
    Impl = TLI.Impl;
    OverrideAsUnavailable = TLI.OverrideAsUnavailable;
    return *this;
  }
  TargetLibraryInfo &operator=(TargetLibraryInfo &&TLI) {
    Impl = TLI.Impl;
    OverrideAsUnavailable = TLI.OverrideAsUnavailable;
    return *this;
  }

  /// Determine whether a callee with the given TLI can be inlined into
  /// caller with this TLI, based on 'nobuiltin' attributes. When requested,
  /// allow inlining into a caller with a superset of the callee's nobuiltin
  /// attributes, which is conservatively correct.
  bool areInlineCompatible(const TargetLibraryInfo &CalleeTLI,
                           bool AllowCallerSuperset) const {
    if (!AllowCallerSuperset)
      return OverrideAsUnavailable == CalleeTLI.OverrideAsUnavailable;
    BitVector B = OverrideAsUnavailable;
    B |= CalleeTLI.OverrideAsUnavailable;
    // We can inline if the union of the caller and callee's nobuiltin
    // attributes is no stricter than the caller's nobuiltin attributes.
    return B == OverrideAsUnavailable;
  }

  /// Searches for a particular function name.
  ///
  /// If it is one of the known library functions, return true and set F to the
  /// corresponding value.
  bool getLibFunc(StringRef funcName, LibFunc &F) const {
    return Impl->getLibFunc(funcName, F);
  }

  bool getLibFunc(const Function &FDecl, LibFunc &F) const {
    return Impl->getLibFunc(FDecl, F);
  }

  /// If a callbase does not have the 'nobuiltin' attribute, return if the
  /// called function is a known library function and set F to that function.
  bool getLibFunc(const CallBase &CB, LibFunc &F) const {
    return !CB.isNoBuiltin() && CB.getCalledFunction() &&
           getLibFunc(*(CB.getCalledFunction()), F);
  }

  /// Disables all builtins.
  ///
  /// This can be used for options like -fno-builtin.
  void disableAllFunctions() LLVM_ATTRIBUTE_UNUSED {
    OverrideAsUnavailable.set();
  }

  /// Forces a function to be marked as unavailable.
  void setUnavailable(LibFunc F) LLVM_ATTRIBUTE_UNUSED {
    OverrideAsUnavailable.set(F);
  }

  TargetLibraryInfoImpl::AvailabilityState getState(LibFunc F) const {
    if (OverrideAsUnavailable[F])
      return TargetLibraryInfoImpl::Unavailable;
    return Impl->getState(F);
  }

  /// Tests whether a library function is available.
  bool has(LibFunc F) const {
    return getState(F) != TargetLibraryInfoImpl::Unavailable;
  }
  bool isFunctionVectorizable(StringRef F, unsigned VF) const {
    return Impl->isFunctionVectorizable(F, VF);
  }
  bool isFunctionVectorizable(StringRef F) const {
    return Impl->isFunctionVectorizable(F);
  }
  StringRef getVectorizedFunction(StringRef F, unsigned VF) const {
    return Impl->getVectorizedFunction(F, VF);
  }

  /// Tests if the function is both available and a candidate for optimized code
  /// generation.
  bool hasOptimizedCodeGen(LibFunc F) const {
    if (getState(F) == TargetLibraryInfoImpl::Unavailable)
      return false;
    switch (F) {
    default: break;
    case LibFunc_copysign:     case LibFunc_copysignf:  case LibFunc_copysignl:
    case LibFunc_fabs:         case LibFunc_fabsf:      case LibFunc_fabsl:
    case LibFunc_sin:          case LibFunc_sinf:       case LibFunc_sinl:
    case LibFunc_cos:          case LibFunc_cosf:       case LibFunc_cosl:
    case LibFunc_sqrt:         case LibFunc_sqrtf:      case LibFunc_sqrtl:
    case LibFunc_sqrt_finite:  case LibFunc_sqrtf_finite:
                                                   case LibFunc_sqrtl_finite:
    case LibFunc_fmax:         case LibFunc_fmaxf:      case LibFunc_fmaxl:
    case LibFunc_fmin:         case LibFunc_fminf:      case LibFunc_fminl:
    case LibFunc_floor:        case LibFunc_floorf:     case LibFunc_floorl:
    case LibFunc_nearbyint:    case LibFunc_nearbyintf: case LibFunc_nearbyintl:
    case LibFunc_ceil:         case LibFunc_ceilf:      case LibFunc_ceill:
    case LibFunc_rint:         case LibFunc_rintf:      case LibFunc_rintl:
    case LibFunc_round:        case LibFunc_roundf:     case LibFunc_roundl:
    case LibFunc_trunc:        case LibFunc_truncf:     case LibFunc_truncl:
    case LibFunc_log2:         case LibFunc_log2f:      case LibFunc_log2l:
    case LibFunc_exp2:         case LibFunc_exp2f:      case LibFunc_exp2l:
    case LibFunc_memcpy:       case LibFunc_memset:     case LibFunc_memmove:
    case LibFunc_memcmp:       case LibFunc_bcmp:       case LibFunc_strcmp:
    case LibFunc_strcpy:       case LibFunc_stpcpy:     case LibFunc_strlen:
    case LibFunc_strnlen:      case LibFunc_memchr:     case LibFunc_mempcpy:
      return true;
    }
    return false;
  }

  StringRef getName(LibFunc F) const {
    auto State = getState(F);
    if (State == TargetLibraryInfoImpl::Unavailable)
      return StringRef();
    if (State == TargetLibraryInfoImpl::StandardName)
      return Impl->StandardNames[F];
    assert(State == TargetLibraryInfoImpl::CustomName);
    return Impl->CustomNames.find(F)->second;
  }

  /// Returns extension attribute kind to be used for i32 parameters
  /// corresponding to C-level int or unsigned int.  May be zeroext, signext,
  /// or none.
  Attribute::AttrKind getExtAttrForI32Param(bool Signed = true) const {
    if (Impl->ShouldExtI32Param)
      return Signed ? Attribute::SExt : Attribute::ZExt;
    if (Impl->ShouldSignExtI32Param)
      return Attribute::SExt;
    return Attribute::None;
  }

  /// Returns extension attribute kind to be used for i32 return values
  /// corresponding to C-level int or unsigned int.  May be zeroext, signext,
  /// or none.
  Attribute::AttrKind getExtAttrForI32Return(bool Signed = true) const {
    if (Impl->ShouldExtI32Return)
      return Signed ? Attribute::SExt : Attribute::ZExt;
    return Attribute::None;
  }

  /// \copydoc TargetLibraryInfoImpl::getWCharSize()
  unsigned getWCharSize(const Module &M) const {
    return Impl->getWCharSize(M);
  }

  /// Handle invalidation from the pass manager.
  ///
  /// If we try to invalidate this info, just return false. It cannot become
  /// invalid even if the module or function changes.
  bool invalidate(Module &, const PreservedAnalyses &,
                  ModuleAnalysisManager::Invalidator &) {
    return false;
  }
  bool invalidate(Function &, const PreservedAnalyses &,
                  FunctionAnalysisManager::Invalidator &) {
    return false;
  }
  /// Returns the largest vectorization factor used in the list of
  /// vector functions.
  unsigned getWidestVF(StringRef ScalarF) const {
    return Impl->getWidestVF(ScalarF);
  }

  /// Check if the function "F" is listed in a library known to LLVM.
  bool isKnownVectorFunctionInLibrary(StringRef F) const {
    return this->isFunctionVectorizable(F);
  }
};

/// Analysis pass providing the \c TargetLibraryInfo.
///
/// Note that this pass's result cannot be invalidated, it is immutable for the
/// life of the module.
class TargetLibraryAnalysis : public AnalysisInfoMixin<TargetLibraryAnalysis> {
public:
  typedef TargetLibraryInfo Result;

  /// Default construct the library analysis.
  ///
  /// This will use the module's triple to construct the library info for that
  /// module.
  TargetLibraryAnalysis() {}

  /// Construct a library analysis with baseline Module-level info.
  ///
  /// This will be supplemented with Function-specific info in the Result.
  TargetLibraryAnalysis(TargetLibraryInfoImpl BaselineInfoImpl)
      : BaselineInfoImpl(std::move(BaselineInfoImpl)) {}

  TargetLibraryInfo run(const Function &F, FunctionAnalysisManager &);

private:
  friend AnalysisInfoMixin<TargetLibraryAnalysis>;
  static AnalysisKey Key;

  Optional<TargetLibraryInfoImpl> BaselineInfoImpl;
};

class TargetLibraryInfoWrapperPass : public ImmutablePass {
  TargetLibraryAnalysis TLA;
  Optional<TargetLibraryInfo> TLI;

  virtual void anchor();

public:
  static char ID;
  TargetLibraryInfoWrapperPass();
  explicit TargetLibraryInfoWrapperPass(const Triple &T);
  explicit TargetLibraryInfoWrapperPass(const TargetLibraryInfoImpl &TLI);

  TargetLibraryInfo &getTLI(const Function &F) {
    FunctionAnalysisManager DummyFAM;
    TLI = TLA.run(F, DummyFAM);
    return *TLI;
  }
};

} // end namespace llvm

#endif