//===- SubtargetFeature.cpp - CPU characteristics Implementation ----------===//

//

//                     The LLVM Compiler Infrastructure

//

// This file is distributed under the University of Illinois Open Source

// License. See LICENSE.TXT for details.

//

//===----------------------------------------------------------------------===//

//

// This file implements the SubtargetFeature interface.

//

//===----------------------------------------------------------------------===//

#include "llvm/MC/SubtargetFeature.h"

#include "llvm/ADT/StringExtras.h"

#include "llvm/Support/Debug.h"

#include "llvm/Support/Format.h"

#include "llvm/Support/raw_ostream.h"

#include <algorithm>

#include <cassert>

#include <cctype>

#include <cstdlib>

using namespace llvm_ks;

//===----------------------------------------------------------------------===//

//                          Static Helper Functions

//===----------------------------------------------------------------------===//

/// hasFlag - Determine if a feature has a flag; '+' or '-'

///

static inline bool hasFlag(StringRef Feature) {

  assert(!Feature.empty() && "Empty string");

  // Get first character

  char Ch = Feature[0];

  // Check if first character is '+' or '-' flag

  return Ch == '+' || Ch =='-';

}

/// StripFlag - Return string stripped of flag.

///

static inline std::string StripFlag(StringRef Feature) {

  return hasFlag(Feature) ? Feature.substr(1) : Feature;

}

/// isEnabled - Return true if enable flag; '+'.

///

static inline bool isEnabled(StringRef Feature) {

  assert(!Feature.empty() && "Empty string");

  // Get first character

  char Ch = Feature[0];

  // Check if first character is '+' for enabled

  return Ch == '+';

}

/// Split - Splits a string of comma separated items in to a vector of strings.

///

static void Split(std::vector<std::string> &V, StringRef S) {

  SmallVector<StringRef, 3> Tmp;

  S.split(Tmp, ',', -1, false /* KeepEmpty */);

  V.assign(Tmp.begin(), Tmp.end());

}

/// Adding features.

void SubtargetFeatures::AddFeature(StringRef String, bool Enable) {

  // Don't add empty features.

  if (!String.empty())

    // Convert to lowercase, prepend flag if we don't already have a flag.

    Features.push_back(hasFlag(String) ? String.lower()

                                       : (Enable ? "+" : "-") + String.lower());

}

/// Find KV in array using binary search.

static const SubtargetFeatureKV *Find(StringRef S,

                                      ArrayRef<SubtargetFeatureKV> A) {

  // Binary search the array

  auto F = std::lower_bound(A.begin(), A.end(), S);

  // If not found then return NULL

  if (F == A.end() || StringRef(F->Key) != S) return nullptr;

  // Return the found array item

  return F;

}

/// getLongestEntryLength - Return the length of the longest entry in the table.

///

static size_t getLongestEntryLength(ArrayRef<SubtargetFeatureKV> Table) {

  size_t MaxLen = 0;

  for (auto &I : Table)

    MaxLen = std::max(MaxLen, std::strlen(I.Key));

  return MaxLen;

}

/// Display help for feature choices.

///

static void Help(ArrayRef<SubtargetFeatureKV> CPUTable,

                 ArrayRef<SubtargetFeatureKV> FeatTable) {

  // Determine the length of the longest CPU and Feature entries.

  unsigned MaxCPULen  = getLongestEntryLength(CPUTable);

  unsigned MaxFeatLen = getLongestEntryLength(FeatTable);

  // Print the CPU table.

  errs() << "Available CPUs for this target:\n\n";

  for (auto &CPU : CPUTable)

    errs() << format("  %-*s - %s.\n", MaxCPULen, CPU.Key, CPU.Desc);

  errs() << '\n';

  // Print the Feature table.

  errs() << "Available features for this target:\n\n";

  for (auto &Feature : FeatTable)

    errs() << format("  %-*s - %s.\n", MaxFeatLen, Feature.Key, Feature.Desc);

  errs() << '\n';

  errs() << "Use +feature to enable a feature, or -feature to disable it.\n"

            "For example, llc -mcpu=mycpu -mattr=+feature1,-feature2\n";

}

//===----------------------------------------------------------------------===//

//                    SubtargetFeatures Implementation

//===----------------------------------------------------------------------===//

SubtargetFeatures::SubtargetFeatures(StringRef Initial) {

  // Break up string into separate features

  Split(Features, Initial);

}

std::string SubtargetFeatures::getString() const {

  return join(Features.begin(), Features.end(), ",");

}

/// SetImpliedBits - For each feature that is (transitively) implied by this

/// feature, set it.

///

static

void SetImpliedBits(FeatureBitset &Bits, const SubtargetFeatureKV *FeatureEntry,

                    ArrayRef<SubtargetFeatureKV> FeatureTable) {

  for (auto &FE : FeatureTable) {

    if (FeatureEntry->Value == FE.Value) continue;

    if ((FeatureEntry->Implies & FE.Value).any()) {

      Bits |= FE.Value;

      SetImpliedBits(Bits, &FE, FeatureTable);

    }

  }

}

/// ClearImpliedBits - For each feature that (transitively) implies this

/// feature, clear it.

///

static

void ClearImpliedBits(FeatureBitset &Bits, 

                      const SubtargetFeatureKV *FeatureEntry,

                      ArrayRef<SubtargetFeatureKV> FeatureTable) {

  for (auto &FE : FeatureTable) {

    if (FeatureEntry->Value == FE.Value) continue;

    if ((FE.Implies & FeatureEntry->Value).any()) {

      Bits &= ~FE.Value;

      ClearImpliedBits(Bits, &FE, FeatureTable);

    }

  }

}

/// ToggleFeature - Toggle a feature and update the feature bits.

void

SubtargetFeatures::ToggleFeature(FeatureBitset &Bits, StringRef Feature,

                                 ArrayRef<SubtargetFeatureKV> FeatureTable) {

  // Find feature in table.

  const SubtargetFeatureKV *FeatureEntry =

      Find(StripFlag(Feature), FeatureTable);

  // If there is a match

  if (FeatureEntry) {

    if ((Bits & FeatureEntry->Value) == FeatureEntry->Value) {

      Bits &= ~FeatureEntry->Value;

      // For each feature that implies this, clear it.

      ClearImpliedBits(Bits, FeatureEntry, FeatureTable);

    } else {

      Bits |=  FeatureEntry->Value;

      // For each feature that this implies, set it.

      SetImpliedBits(Bits, FeatureEntry, FeatureTable);

    }

  } else {

    errs() << "'" << Feature

           << "' is not a recognized feature for this target"

           << " (ignoring feature)\n";

  }

}

void SubtargetFeatures::ApplyFeatureFlag(FeatureBitset &Bits, StringRef Feature,

                                    ArrayRef<SubtargetFeatureKV> FeatureTable) {

  assert(hasFlag(Feature));

  // Find feature in table.

  const SubtargetFeatureKV *FeatureEntry =

      Find(StripFlag(Feature), FeatureTable);

  // If there is a match

  if (FeatureEntry) {

    // Enable/disable feature in bits

    if (isEnabled(Feature)) {

      Bits |= FeatureEntry->Value;

      // For each feature that this implies, set it.

      SetImpliedBits(Bits, FeatureEntry, FeatureTable);

    } else {

      Bits &= ~FeatureEntry->Value;

      // For each feature that implies this, clear it.

      ClearImpliedBits(Bits, FeatureEntry, FeatureTable);

    }

  } else {

    errs() << "'" << Feature

           << "' is not a recognized feature for this target"

           << " (ignoring feature)\n";

  }

}

/// getFeatureBits - Get feature bits a CPU.

///

FeatureBitset

SubtargetFeatures::getFeatureBits(StringRef CPU,

                                  ArrayRef<SubtargetFeatureKV> CPUTable,

                                  ArrayRef<SubtargetFeatureKV> FeatureTable) {

  if (CPUTable.empty() || FeatureTable.empty())

    return FeatureBitset();

#ifndef NDEBUG

  assert(std::is_sorted(std::begin(CPUTable), std::end(CPUTable)) &&

         "CPU table is not sorted");

  assert(std::is_sorted(std::begin(FeatureTable), std::end(FeatureTable)) &&

         "CPU features table is not sorted");

#endif

  // Resulting bits

  FeatureBitset Bits;

  // Check if help is needed

  if (CPU == "help")

    Help(CPUTable, FeatureTable);

  // Find CPU entry if CPU name is specified.

  else if (!CPU.empty()) {

    const SubtargetFeatureKV *CPUEntry = Find(CPU, CPUTable);

    // If there is a match

    if (CPUEntry) {

      // Set base feature bits

      Bits = CPUEntry->Value;

      // Set the feature implied by this CPU feature, if any.

      for (auto &FE : FeatureTable) {

        if ((CPUEntry->Value & FE.Value).any())

          SetImpliedBits(Bits, &FE, FeatureTable);

      }

    } else {

      errs() << "'" << CPU

             << "' is not a recognized processor for this target"

             << " (ignoring processor)\n";

    }

  }

  // Iterate through each feature

  for (auto &Feature : Features) {

    // Check for help

    if (Feature == "+help")

      Help(CPUTable, FeatureTable);

    ApplyFeatureFlag(Bits, Feature, FeatureTable);

  }

  return Bits;

}

/// print - Print feature string.

///

void SubtargetFeatures::print(raw_ostream &OS) const {

  for (auto &F : Features)

    OS << F << " ";

  OS << "\n";

}

#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)

/// dump - Dump feature info.

///

LLVM_DUMP_METHOD void SubtargetFeatures::dump() const {

}

#endif

/// Adds the default features for the specified target triple.

///

/// FIXME: This is an inelegant way of specifying the features of a

/// subtarget. It would be better if we could encode this information

/// into the IR. See <rdar://5972456>.

///

void SubtargetFeatures::getDefaultSubtargetFeatures(const Triple& Triple) {

  if (Triple.getVendor() == Triple::Apple) {

    if (Triple.getArch() == Triple::ppc) {

      // powerpc-apple-*

      AddFeature("altivec");

    } else if (Triple.getArch() == Triple::ppc64) {

      // powerpc64-apple-*

      AddFeature("64bit");

      AddFeature("altivec");

    }

  }

}