Builtins.cpp

//===--- Builtins.cpp - Builtin function implementation -------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
//  This file implements various things for builtin functions.
//
//===----------------------------------------------------------------------===//

#include "clang/Basic/Builtins.h"
#include "BuiltinTargetFeatures.h"
#include "clang/Basic/IdentifierTable.h"
#include "clang/Basic/LangOptions.h"
#include "clang/Basic/TargetInfo.h"
#include "llvm/ADT/StringRef.h"
using namespace clang;

const char *HeaderDesc::getName() const {
  switch (ID) {
#define HEADER(ID, NAME)                                                       \
  case ID:                                                                     \
    return NAME;
#include "clang/Basic/BuiltinHeaders.def"
#undef HEADER
  };
  llvm_unreachable("Unknown HeaderDesc::HeaderID enum");
}

static constexpr auto BuiltinStorage =
    Builtin::Storage<Builtin::FirstTSBuiltin>::Make(
        CLANG_BUILTIN_STR_TABLE("not a builtin function", "", "")
#define BUILTIN CLANG_BUILTIN_STR_TABLE
#include "clang/Basic/Builtins.inc"
            ,
        {CLANG_BUILTIN_ENTRY("not a builtin function", "", "")
#define BUILTIN CLANG_BUILTIN_ENTRY
#define LANGBUILTIN CLANG_LANGBUILTIN_ENTRY
#define LIBBUILTIN CLANG_LIBBUILTIN_ENTRY
#include "clang/Basic/Builtins.inc"
        });

std::pair<const char *, const Builtin::Info &>
Builtin::Context::getStrTableAndInfo(unsigned ID) const {
  if (ID < Builtin::FirstTSBuiltin)
    return {BuiltinStorage.StringTable, BuiltinStorage.Infos[ID]};
  assert(
      ((ID - Builtin::FirstTSBuiltin) < (TSInfos.size() + AuxTSInfos.size())) &&
      "Invalid builtin ID!");
  if (isAuxBuiltinID(ID))
    return {AuxTSStrTable,
            AuxTSInfos[getAuxBuiltinID(ID) - Builtin::FirstTSBuiltin]};
  return {TSStrTable, TSInfos[ID - Builtin::FirstTSBuiltin]};
}

static llvm::StringRef getStrFromTable(const char *StrTable, int Offset) {
  return &StrTable[Offset];
}

/// Return the identifier name for the specified builtin,
/// e.g. "__builtin_abs".
llvm::StringRef Builtin::Context::getName(unsigned ID) const {
  const auto &[StrTable, I] = getStrTableAndInfo(ID);
  return getStrFromTable(StrTable, I.Offsets.Name);
}

const char *Builtin::Context::getTypeString(unsigned ID) const {
  const auto &[StrTable, I] = getStrTableAndInfo(ID);
  return getStrFromTable(StrTable, I.Offsets.Type).data();
}

const char *Builtin::Context::getAttributesString(unsigned ID) const {
  const auto &[StrTable, I] = getStrTableAndInfo(ID);
  return getStrFromTable(StrTable, I.Offsets.Attributes).data();
}

const char *Builtin::Context::getRequiredFeatures(unsigned ID) const {
  const auto &[StrTable, I] = getStrTableAndInfo(ID);
  return getStrFromTable(StrTable, I.Offsets.Features).data();
}

void Builtin::Context::InitializeTarget(const TargetInfo &Target,
                                        const TargetInfo *AuxTarget) {
  assert(TSStrTable == nullptr && "Already initialized target?");
  assert(TSInfos.empty() && "Already initialized target?");
  std::tie(TSStrTable, TSInfos) = Target.getTargetBuiltinStorage();
  if (AuxTarget) {
    std::tie(AuxTSStrTable, AuxTSInfos) = AuxTarget->getTargetBuiltinStorage();
  }
}

bool Builtin::Context::isBuiltinFunc(llvm::StringRef FuncName) {
  bool InStdNamespace = FuncName.consume_front("std-");
  const char *StrTable = BuiltinStorage.StringTable;
  for (unsigned i = Builtin::NotBuiltin + 1; i != Builtin::FirstTSBuiltin;
       ++i) {
    const auto &I = BuiltinStorage.Infos[i];
    if (FuncName == getStrFromTable(StrTable, I.Offsets.Name) &&
        (bool)strchr(getStrFromTable(StrTable, I.Offsets.Attributes).data(),
                     'z') == InStdNamespace)
      return strchr(getStrFromTable(StrTable, I.Offsets.Attributes).data(),
                    'f') != nullptr;
  }

  return false;
}

/// Is this builtin supported according to the given language options?
static bool builtinIsSupported(const char *StrTable,
                               const Builtin::Info &BuiltinInfo,
                               const LangOptions &LangOpts) {
  auto AttributesStr =
      getStrFromTable(StrTable, BuiltinInfo.Offsets.Attributes);

  /* Builtins Unsupported */
  if (LangOpts.NoBuiltin && strchr(AttributesStr.data(), 'f') != nullptr)
    return false;
  /* CorBuiltins Unsupported */
  if (!LangOpts.Coroutines && (BuiltinInfo.Langs & COR_LANG))
    return false;
  /* MathBuiltins Unsupported */
  if (LangOpts.NoMathBuiltin && BuiltinInfo.Header.ID == HeaderDesc::MATH_H)
    return false;
  /* GnuMode Unsupported */
  if (!LangOpts.GNUMode && (BuiltinInfo.Langs & GNU_LANG))
    return false;
  /* MSMode Unsupported */
  if (!LangOpts.MicrosoftExt && (BuiltinInfo.Langs & MS_LANG))
    return false;
  /* HLSLMode Unsupported */
  if (!LangOpts.HLSL && (BuiltinInfo.Langs & HLSL_LANG))
    return false;
  /* ObjC Unsupported */
  if (!LangOpts.ObjC && BuiltinInfo.Langs == OBJC_LANG)
    return false;
  /* OpenCLC Unsupported */
  if (!LangOpts.OpenCL && (BuiltinInfo.Langs & ALL_OCL_LANGUAGES))
    return false;
  /* OopenCL GAS Unsupported */
  if (!LangOpts.OpenCLGenericAddressSpace && (BuiltinInfo.Langs & OCL_GAS))
    return false;
  /* OpenCL Pipe Unsupported */
  if (!LangOpts.OpenCLPipes && (BuiltinInfo.Langs & OCL_PIPE))
    return false;

  // Device side enqueue is not supported until OpenCL 2.0. In 2.0 and higher
  // support is indicated with language option for blocks.

  /* OpenCL DSE Unsupported */
  if ((LangOpts.getOpenCLCompatibleVersion() < 200 || !LangOpts.Blocks) &&
      (BuiltinInfo.Langs & OCL_DSE))
    return false;
  /* OpenMP Unsupported */
  if (!LangOpts.OpenMP && BuiltinInfo.Langs == OMP_LANG)
    return false;
  /* CUDA Unsupported */
  if (!LangOpts.CUDA && BuiltinInfo.Langs == CUDA_LANG)
    return false;
  /* CPlusPlus Unsupported */
  if (!LangOpts.CPlusPlus && BuiltinInfo.Langs == CXX_LANG)
    return false;
  /* consteval Unsupported */
  if (!LangOpts.CPlusPlus20 && strchr(AttributesStr.data(), 'G') != nullptr)
    return false;
  return true;
}

/// initializeBuiltins - Mark the identifiers for all the builtins with their
/// appropriate builtin ID # and mark any non-portable builtin identifiers as
/// such.
void Builtin::Context::initializeBuiltins(IdentifierTable &Table,
                                          const LangOptions& LangOpts) {
  // Step #1: mark all target-independent builtins with their ID's.
  for (const auto &&[Index, I] :
       llvm::enumerate(llvm::ArrayRef(BuiltinStorage.Infos).drop_front()))
    if (builtinIsSupported(BuiltinStorage.StringTable, I, LangOpts)) {
      Table.get(getStrFromTable(BuiltinStorage.StringTable, I.Offsets.Name))
          .setBuiltinID(Index + 1);
    }

  // Step #2: Register target-specific builtins.
  for (const auto &&[Index, I] : llvm::enumerate(TSInfos))
    if (builtinIsSupported(TSStrTable, I, LangOpts))
      Table.get(getStrFromTable(TSStrTable, I.Offsets.Name))
          .setBuiltinID(Index + Builtin::FirstTSBuiltin);

  // Step #3: Register target-specific builtins for AuxTarget.
  for (const auto &&[Index, I] : llvm::enumerate(AuxTSInfos))
    Table.get(getStrFromTable(AuxTSStrTable, I.Offsets.Name))
        .setBuiltinID(Index + Builtin::FirstTSBuiltin + TSInfos.size());

  // Step #4: Unregister any builtins specified by -fno-builtin-foo.
  for (llvm::StringRef Name : LangOpts.NoBuiltinFuncs) {
    bool InStdNamespace = Name.consume_front("std-");
    auto NameIt = Table.find(Name);
    if (NameIt != Table.end()) {
      unsigned ID = NameIt->second->getBuiltinID();
      if (ID != Builtin::NotBuiltin && isPredefinedLibFunction(ID) &&
          isInStdNamespace(ID) == InStdNamespace) {
        NameIt->second->clearBuiltinID();
      }
    }
  }
}

unsigned Builtin::Context::getRequiredVectorWidth(unsigned ID) const {
  const char *WidthPos = ::strchr(getAttributesString(ID), 'V');
  if (!WidthPos)
    return 0;

  ++WidthPos;
  assert(*WidthPos == ':' &&
         "Vector width specifier must be followed by a ':'");
  ++WidthPos;

  char *EndPos;
  unsigned Width = ::strtol(WidthPos, &EndPos, 10);
  assert(*EndPos == ':' && "Vector width specific must end with a ':'");
  return Width;
}

bool Builtin::Context::isLike(unsigned ID, unsigned &FormatIdx,
                              bool &HasVAListArg, const char *Fmt) const {
  assert(Fmt && "Not passed a format string");
  assert(::strlen(Fmt) == 2 &&
         "Format string needs to be two characters long");
  assert(::toupper(Fmt[0]) == Fmt[1] &&
         "Format string is not in the form \"xX\"");

  const char *Like = ::strpbrk(getAttributesString(ID), Fmt);
  if (!Like)
    return false;

  HasVAListArg = (*Like == Fmt[1]);

  ++Like;
  assert(*Like == ':' && "Format specifier must be followed by a ':'");
  ++Like;

  assert(::strchr(Like, ':') && "Format specifier must end with a ':'");
  FormatIdx = ::strtol(Like, nullptr, 10);
  return true;
}

bool Builtin::Context::isPrintfLike(unsigned ID, unsigned &FormatIdx,
                                    bool &HasVAListArg) {
  return isLike(ID, FormatIdx, HasVAListArg, "pP");
}

bool Builtin::Context::isScanfLike(unsigned ID, unsigned &FormatIdx,
                                   bool &HasVAListArg) {
  return isLike(ID, FormatIdx, HasVAListArg, "sS");
}

bool Builtin::Context::performsCallback(unsigned ID,
                                        SmallVectorImpl<int> &Encoding) const {
  const char *CalleePos = ::strchr(getAttributesString(ID), 'C');
  if (!CalleePos)
    return false;

  ++CalleePos;
  assert(*CalleePos == '<' &&
         "Callback callee specifier must be followed by a '<'");
  ++CalleePos;

  char *EndPos;
  int CalleeIdx = ::strtol(CalleePos, &EndPos, 10);
  assert(CalleeIdx >= 0 && "Callee index is supposed to be positive!");
  Encoding.push_back(CalleeIdx);

  while (*EndPos == ',') {
    const char *PayloadPos = EndPos + 1;

    int PayloadIdx = ::strtol(PayloadPos, &EndPos, 10);
    Encoding.push_back(PayloadIdx);
  }

  assert(*EndPos == '>' && "Callback callee specifier must end with a '>'");
  return true;
}

bool Builtin::Context::canBeRedeclared(unsigned ID) const {
  return ID == Builtin::NotBuiltin || ID == Builtin::BI__va_start ||
         ID == Builtin::BI__builtin_assume_aligned ||
         (!hasReferenceArgsOrResult(ID) && !hasCustomTypechecking(ID)) ||
         isInStdNamespace(ID);
}

bool Builtin::evaluateRequiredTargetFeatures(
    StringRef RequiredFeatures, const llvm::StringMap<bool> &TargetFetureMap) {
  // Return true if the builtin doesn't have any required features.
  if (RequiredFeatures.empty())
    return true;
  assert(!RequiredFeatures.contains(' ') && "Space in feature list");

  TargetFeatures TF(TargetFetureMap);
  return TF.hasRequiredFeatures(RequiredFeatures);
}