lib/Target/SubtargetFeature.cpp

//===- SubtargetFeature.cpp - CPU characteristics Implementation ----------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file was developed by Jim Laskey and is distributed under the 
// University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the SubtargetFeature interface.
//
//===----------------------------------------------------------------------===//

#include "llvm/Target/SubtargetFeature.h"
#include "llvm/ADT/StringExtras.h"
#include <algorithm>
#include <cassert>
#include <cctype>
#include <iostream>
using namespace llvm;

//===----------------------------------------------------------------------===//
//                          Static Helper Functions
//===----------------------------------------------------------------------===//

/// hasFlag - Determine if a feature has a flag; '+' or '-'
///
static inline bool hasFlag(const std::string &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(const std::string &Feature) {
  return hasFlag(Feature) ? Feature.substr(1) : Feature;
}

/// isEnabled - Return true if enable flag; '+'.
///
static inline bool isEnabled(const std::string &Feature) {
  assert(!Feature.empty() && "Empty string");
  // Get first character
  char Ch = Feature[0];
  // Check if first character is '+' for enabled
  return Ch == '+';
}

/// PrependFlag - Return a string with a prepended flag; '+' or '-'.
///
static inline std::string PrependFlag(const std::string &Feature,
                                      bool IsEnabled) {
  assert(!Feature.empty() && "Empty string");
  if (hasFlag(Feature)) return Feature;
  return std::string(IsEnabled ? "+" : "-") + Feature;
}

/// Split - Splits a string of comma separated items in to a vector of strings.
///
static void Split(std::vector<std::string> &V, const std::string &S) {
  // Start at beginning of string.
  size_t Pos = 0;
  while (true) {
    // Find the next comma
    size_t Comma = S.find(',', Pos);
    // If no comma found then the the rest of the string is used
    if (Comma == std::string::npos) {
      // Add string to vector
      V.push_back(S.substr(Pos));
      break;
    }
    // Otherwise add substring to vector
    V.push_back(S.substr(Pos, Comma - Pos));
    // Advance to next item
    Pos = Comma + 1;
  }
}

/// Join a vector of strings to a string with a comma separating each element.
///
static std::string Join(const std::vector<std::string> &V) {
  // Start with empty string.
  std::string Result;
  // If the vector is not empty 
  if (!V.empty()) {
    // Start with the CPU feature
    Result = V[0];
    // For each successive feature
    for (size_t i = 1; i < V.size(); i++) {
      // Add a comma
      Result += ",";
      // Add the feature
      Result += V[i];
    }
  }
  // Return the features string 
  return Result;
}

/// Adding features.
void SubtargetFeatures::AddFeature(const std::string &String,
                                   bool IsEnabled) {
  // Don't add empty features
  if (!String.empty()) {
    // Convert to lowercase, prepend flag and add to vector
    Features.push_back(PrependFlag(LowercaseString(String), IsEnabled));
  }
}

/// Find item in array using binary search.
static const SubtargetFeatureKV *Find(const std::string &S,
                                      const SubtargetFeatureKV *A, size_t L) {
  // Determine the end of the array
  const SubtargetFeatureKV *Hi = A + L;
  // Binary search the array
  const SubtargetFeatureKV *F = std::lower_bound(A, Hi, S);
  // If not found then return NULL
  if (F == Hi || std::string(F->Key) != S) return NULL;
  // Return the found array item
  return F;
}

/// Display help for feature choices.
///
static void Help(bool isFeature, const SubtargetFeatureKV *Table,
                 size_t TableSize) {
  // Determine the length of the longest key.
  size_t MaxLen = 0;
  for (size_t i = 0; i < TableSize; i++)
    MaxLen = std::max(MaxLen, std::strlen(Table[i].Key));
  
  std::cerr << "Available " << (isFeature ? "features" : "CPUs")
            << " for this target:\n\n";

  for (size_t i = 0; i < TableSize; i++) {
    // Compute required padding
    size_t Pad = MaxLen - std::strlen(Table[i].Key);
    std::cerr << Table[i].Key << std::string(Pad, ' ') << " - "
              << Table[i].Desc << ".\n";
  }

  std::cerr << "\n";
  if (isFeature) {
    std::cerr
      << "Use +feature to enable a feature, or -feature to disable it.\n"
      << "For example, llc -mcpu=mycpu -mattr=+feature1,-feature2\n";
  }
  exit(1);
}

//===----------------------------------------------------------------------===//
//                    SubtargetFeatures Implementation
//===----------------------------------------------------------------------===//

SubtargetFeatures::SubtargetFeatures(const std::string &Initial) {
  // Break up string into separate features
  Split(Features, Initial);
}


std::string SubtargetFeatures::getString() const {
  return Join(Features);
}
void SubtargetFeatures::setString(const std::string &Initial) {
  // Throw out old features
  Features.clear();
  // Break up string into separate features
  Split(Features, LowercaseString(Initial));
}

/// setCPU - Set the CPU string.  Replaces previous setting.  Setting to "" 
/// clears CPU.
void SubtargetFeatures::setCPU(const std::string &String) {
  Features[0] = LowercaseString(String);
}



/// Parse feature string for quick usage.
///
uint32_t SubtargetFeatures::Parse(const std::string &String,
                                  const std::string &DefaultCPU,
                                  const SubtargetFeatureKV *CPUTable,
                                  size_t CPUTableSize,
                                  const SubtargetFeatureKV *FeatureTable,
                                  size_t FeatureTableSize) {
  assert(CPUTable && "missing CPU table");
  assert(FeatureTable && "missing features table");
#ifndef NDEBUG
  for (size_t i = 1; i < CPUTableSize; i++) {
    assert(strcmp(CPUTable[i - 1].Key, CPUTable[i].Key) < 0 &&
           "CPU table is not sorted");
  }
  for (size_t i = 1; i < FeatureTableSize; i++) {
    assert(strcmp(FeatureTable[i - 1].Key, FeatureTable[i].Key) < 0 &&
          "CPU features table is not sorted");
  }
#endif
  std::vector<std::string> Features;    // Subtarget features as a vector
  uint32_t Bits = 0;                    // Resulting bits
  // Split up features
  Split(Features, String);
  // Check if default is needed
  if (Features[0].empty()) Features[0] = DefaultCPU;
  // Check for help
  if (Features[0] == "help") Help(false, CPUTable, CPUTableSize);
  // Find CPU entry
  const SubtargetFeatureKV *CPUEntry =
                            Find(Features[0], CPUTable, CPUTableSize);
  // If there is a match
  if (CPUEntry) {
    // Set base feature bits
    Bits = CPUEntry->Value;
  } else {
    std::cerr << "'" << Features[0]
              << "' is not a recognized processor for this target"
              << " (ignoring processor)"
              << "\n";
  }
  // Iterate through each feature
  for (size_t i = 1; i < Features.size(); i++) {
    // Get next feature
    const std::string &Feature = Features[i];
    // Check for help
    if (Feature == "+help") Help(true, FeatureTable, FeatureTableSize);
    // Find feature in table.
    const SubtargetFeatureKV *FeatureEntry =
                       Find(StripFlag(Feature), FeatureTable, FeatureTableSize);
    // If there is a match
    if (FeatureEntry) {
      // Enable/disable feature in bits
      if (isEnabled(Feature)) Bits |=  FeatureEntry->Value;
      else                    Bits &= ~FeatureEntry->Value;
    } else {
      std::cerr << "'" << Feature
                << "' is not a recognized feature for this target"
                << " (ignoring feature)"
                << "\n";
    }
  }
  return Bits;
}

/// Print feature string.
void SubtargetFeatures::print(std::ostream &OS) const {
  for (size_t i = 0; i < Features.size(); i++) {
    OS << Features[i] << "  ";
  }
  OS << "\n";
}

/// Dump feature info.
void SubtargetFeatures::dump() const {
  print(std::cerr);
}