//===-- targetmachine.cpp -------------------------------------------------===//
//
//                         LDC – the LLVM D compiler
//
// This file is distributed under the BSD-style LDC license. See the LICENSE
// file for details.
//
//===----------------------------------------------------------------------===//
//
// Note: The target CPU detection logic has been adapted from Clang
// (Tools.cpp and ToolChain.cpp in lib/Driver, the latter seems to have the
// more up-to-date version).
//
//===----------------------------------------------------------------------===//

#include "driver/targetmachine.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/ADT/Triple.h"
#include "llvm/MC/SubtargetFeature.h"
#include "llvm/Support/Host.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/TargetRegistry.h"
#include "llvm/Support/TargetSelect.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#include "mars.h"
#include "gen/logger.h"

#if LDC_LLVM_VER >= 307
#include "driver/cl_options.h"

static const char *getABI(const llvm::Triple &triple) {
  llvm::StringRef ABIName(opts::mABI);
  if (ABIName != "") {
    switch (triple.getArch()) {
    case llvm::Triple::arm:
    case llvm::Triple::armeb:
      if (ABIName.startswith("aapcs"))
        return "aapcs";
      if (ABIName.startswith("eabi"))
        return "apcs";
      break;
    case llvm::Triple::mips:
    case llvm::Triple::mipsel:
    case llvm::Triple::mips64:
    case llvm::Triple::mips64el:
      if (ABIName.startswith("o32"))
        return "o32";
      if (ABIName.startswith("n32"))
        return "n32";
      if (ABIName.startswith("n64"))
        return "n64";
      if (ABIName.startswith("eabi"))
        return "eabi";
      break;
    case llvm::Triple::ppc64:
    case llvm::Triple::ppc64le:
      if (ABIName.startswith("elfv1"))
        return "elfv1";
      if (ABIName.startswith("elfv2"))
        return "elfv2";
      break;
    default:
      break;
    }
    warning(Loc(), "Unknown ABI %s - using default ABI instead",
            ABIName.str().c_str());
  }

  switch (triple.getArch()) {
  case llvm::Triple::mips64:
  case llvm::Triple::mips64el:
    return "n32";
  case llvm::Triple::ppc64:
    return "elfv1";
  case llvm::Triple::ppc64le:
    return "elfv2";
  default:
    return "";
  }
}
#endif

extern llvm::TargetMachine *gTargetMachine;

MipsABI::Type getMipsABI() {
#if LDC_LLVM_VER >= 307
  // eabi can only be set on the commandline
  if (strncmp(opts::mABI.c_str(), "eabi", 4) == 0)
    return MipsABI::EABI;
  else {
#if LDC_LLVM_VER >= 308
    const llvm::DataLayout dl = gTargetMachine->createDataLayout();
#else
    const llvm::DataLayout &dl = *gTargetMachine->getDataLayout();
#endif
    if (dl.getPointerSizeInBits() == 64)
      return MipsABI::N64;
#if LDC_LLVM_VER >= 309
    else if (dl.getLargestLegalIntTypeSizeInBits() == 64)
#else
    else if (dl.getLargestLegalIntTypeSize() == 64)
#endif
      return MipsABI::N32;
    else
      return MipsABI::O32;
  }
#else
  llvm::StringRef features = gTargetMachine->getTargetFeatureString();
  if (features.find("+o32") != std::string::npos) {
    return MipsABI::O32;
  }
  if (features.find("+n32") != std::string::npos) {
    return MipsABI::N32;
  }
  if (features.find("+n64") != std::string::npos) {
    return MipsABI::N32;
  }
  if (features.find("+eabi") != std::string::npos) {
    return MipsABI::EABI;
  }
  return MipsABI::Unknown;
#endif
}

static std::string getX86TargetCPU(const llvm::Triple &triple) {
  // Select the default CPU if none was given (or detection failed).

  // Intel Macs are relatively recent, take advantage of that.
  if (triple.isOSDarwin()) {
    return triple.isArch64Bit() ? "core2" : "yonah";
  }
  // Everything else goes to x86-64 in 64-bit mode.
  if (triple.isArch64Bit()) {
    return "x86-64";
  }
  if (triple.getOSName().startswith("haiku")) {
    return "i586";
  }
  if (triple.getOSName().startswith("openbsd")) {
    return "i486";
  }
  if (triple.getOSName().startswith("bitrig")) {
    return "i686";
  }
  if (triple.getOSName().startswith("freebsd")) {
    return "i486";
  }
  if (triple.getOSName().startswith("netbsd")) {
    return "i486";
  }
  if (triple.getOSName().startswith("openbsd")) {
    return "i486";
  }
  if (triple.getOSName().startswith("dragonfly")) {
    return "i486";
  }
  // All x86 devices running Android have core2 as their common
  // denominator. This makes a better choice than pentium4.
  if (triple.getEnvironment() == llvm::Triple::Android) {
    return "core2";

    // Fallback to p4.
  }
  return "pentium4";
}

static std::string getARMTargetCPU(const llvm::Triple &triple) {
  const char *result = llvm::StringSwitch<const char *>(triple.getArchName())
                           .Cases("armv2", "armv2a", "arm2")
                           .Case("armv3", "arm6")
                           .Case("armv3m", "arm7m")
                           .Case("armv4", "strongarm")
                           .Case("armv4t", "arm7tdmi")
                           .Cases("armv5", "armv5t", "arm10tdmi")
                           .Cases("armv5e", "armv5te", "arm1026ejs")
                           .Case("armv5tej", "arm926ej-s")
                           .Cases("armv6", "armv6k", "arm1136jf-s")
                           .Case("armv6j", "arm1136j-s")
                           .Cases("armv6z", "armv6zk", "arm1176jzf-s")
                           .Case("armv6t2", "arm1156t2-s")
                           .Cases("armv6m", "armv6-m", "cortex-m0")
                           .Cases("armv7", "armv7a", "armv7-a", "cortex-a8")
                           .Cases("armv7l", "armv7-l", "cortex-a8")
                           .Cases("armv7f", "armv7-f", "cortex-a9-mp")
                           .Cases("armv7s", "armv7-s", "swift")
                           .Cases("armv7r", "armv7-r", "cortex-r4")
                           .Cases("armv7m", "armv7-m", "cortex-m3")
                           .Cases("armv7em", "armv7e-m", "cortex-m4")
                           .Cases("armv8", "armv8a", "armv8-a", "cortex-a53")
                           .Case("ep9312", "ep9312")
                           .Case("iwmmxt", "iwmmxt")
                           .Case("xscale", "xscale")
                           // If all else failed, return the most base CPU with
                           // thumb interworking
                           // supported by LLVM.
                           .Default(nullptr);

  if (result) {
    return result;
  }

  return (triple.getEnvironment() == llvm::Triple::GNUEABIHF) ? "arm1176jzf-s"
                                                              : "arm7tdmi";
}

/// Returns the LLVM name of the target CPU to use given the provided
/// -mcpu argument and target triple.
static std::string getTargetCPU(const std::string &cpu,
                                const llvm::Triple &triple) {
  if (!cpu.empty()) {
    if (cpu != "native") {
      return cpu;
    }

    // FIXME: Reject attempts to use -mcpu=native unless the target matches
    // the host.
    std::string hostCPU = llvm::sys::getHostCPUName();
    if (!hostCPU.empty() && hostCPU != "generic") {
      return hostCPU;
    }
  }

  switch (triple.getArch()) {
  default:
    // We don't know about the specifics of this platform, just return the
    // empty string and let LLVM decide.
    return cpu;
  case llvm::Triple::x86:
  case llvm::Triple::x86_64:
    return getX86TargetCPU(triple);
  case llvm::Triple::arm:
    return getARMTargetCPU(triple);
  }
}

static const char *getLLVMArchSuffixForARM(llvm::StringRef CPU) {
  return llvm::StringSwitch<const char *>(CPU)
      .Case("strongarm", "v4")
      .Cases("arm7tdmi", "arm7tdmi-s", "arm710t", "v4t")
      .Cases("arm720t", "arm9", "arm9tdmi", "v4t")
      .Cases("arm920", "arm920t", "arm922t", "v4t")
      .Cases("arm940t", "ep9312", "v4t")
      .Cases("arm10tdmi", "arm1020t", "v5")
      .Cases("arm9e", "arm926ej-s", "arm946e-s", "v5e")
      .Cases("arm966e-s", "arm968e-s", "arm10e", "v5e")
      .Cases("arm1020e", "arm1022e", "xscale", "iwmmxt", "v5e")
      .Cases("arm1136j-s", "arm1136jf-s", "arm1176jz-s", "v6")
      .Cases("arm1176jzf-s", "mpcorenovfp", "mpcore", "v6")
      .Cases("arm1156t2-s", "arm1156t2f-s", "v6t2")
      .Cases("cortex-a5", "cortex-a7", "cortex-a8", "v7")
      .Cases("cortex-a9", "cortex-a12", "cortex-a15", "v7")
      .Cases("cortex-r4", "cortex-r5", "v7r")
      .Case("cortex-m0", "v6m")
      .Case("cortex-m3", "v7m")
      .Case("cortex-m4", "v7em")
      .Case("cortex-a9-mp", "v7f")
      .Case("swift", "v7s")
      .Case("cortex-a53", "v8")
      .Case("krait", "v7")
      .Default("");
}

static FloatABI::Type getARMFloatABI(const llvm::Triple &triple,
                                     const char *llvmArchSuffix) {
  switch (triple.getOS()) {
  case llvm::Triple::Darwin:
  case llvm::Triple::MacOSX:
  case llvm::Triple::IOS: {
    // Darwin defaults to "softfp" for v6 and v7.
    if (llvm::StringRef(llvmArchSuffix).startswith("v6") ||
        llvm::StringRef(llvmArchSuffix).startswith("v7")) {
      return FloatABI::SoftFP;
    }
    return FloatABI::Soft;
  }

  case llvm::Triple::FreeBSD:
    // FreeBSD defaults to soft float
    return FloatABI::Soft;

  default:
    if (triple.getVendorName().startswith("hardfloat"))
      return FloatABI::Hard;
    if (triple.getVendorName().startswith("softfloat"))
      return FloatABI::SoftFP;

    switch (triple.getEnvironment()) {
    case llvm::Triple::GNUEABIHF:
      return FloatABI::Hard;
    case llvm::Triple::GNUEABI:
      return FloatABI::SoftFP;
    case llvm::Triple::EABI:
      // EABI is always AAPCS, and if it was not marked 'hard', it's softfp
      return FloatABI::SoftFP;
    case llvm::Triple::Android: {
      if (llvm::StringRef(llvmArchSuffix).startswith("v7")) {
        return FloatABI::SoftFP;
      }
      return FloatABI::Soft;
    }
    default:
      // Assume "soft".
      // TODO: Warn the user we are guessing.
      return FloatABI::Soft;
    }
  }
}

#if LDC_LLVM_VER < 307
/// Sanitizes the MIPS ABI in the feature string.
static void addMipsABI(const llvm::Triple &triple,
                       std::vector<std::string> &attrs) {
  enum ABI { O32 = 1 << 0, N32 = 1 << 1, N64 = 1 << 2, EABI = 1 << 3 };
  const bool is64Bit = triple.getArch() == llvm::Triple::mips64 ||
                       triple.getArch() == llvm::Triple::mips64el;
  const uint32_t defaultABI = is64Bit ? N64 : O32;
  uint32_t bits = defaultABI;
  auto I = attrs.begin();
  while (I != attrs.end()) {
    std::string str = *I;
    bool enabled = str[0] == '+';
    std::string flag = (str[0] == '+' || str[0] == '-') ? str.substr(1) : str;
    uint32_t newBit = 0;
    if (flag == "o32") {
      newBit = O32;
    }
    if (flag == "n32") {
      newBit = N32;
    }
    if (flag == "n64") {
      newBit = N64;
    }
    if (flag == "eabi") {
      newBit = EABI;
    }
    if (newBit) {
      I = attrs.erase(I);
      if (enabled) {
        bits |= newBit;
      } else {
        bits &= ~newBit;
      }
    } else {
      ++I;
    }
  }
  switch (bits) {
  case O32:
    attrs.push_back("+o32");
    break;
  case N32:
    attrs.push_back("+n32");
    break;
  case N64:
    attrs.push_back("+n64");
    break;
  case EABI:
    attrs.push_back("+eabi");
    break;
  default:
    error(Loc(), "Only one ABI argument is supported");
    fatal();
  }
  if (bits != defaultABI) {
    attrs.push_back(is64Bit ? "-n64" : "-o32");
  }
}
#endif

/// Looks up a target based on an arch name and a target triple.
///
/// If the arch name is non-empty, then the lookup is done by arch. Otherwise,
/// the target triple is used.
///
/// This has been adapted from the corresponding LLVM 3.2+ overload of
/// llvm::TargetRegistry::lookupTarget. Once support for LLVM 3.1 is dropped,
/// the registry method can be used instead.
const llvm::Target *lookupTarget(const std::string &arch, llvm::Triple &triple,
                                 std::string &errorMsg) {
  // Allocate target machine. First, check whether the user has explicitly
  // specified an architecture to compile for. If so we have to look it up by
  // name, because it might be a backend that has no mapping to a target triple.
  const llvm::Target *target = nullptr;
  if (!arch.empty()) {
#if LDC_LLVM_VER >= 307
    for (const llvm::Target &T : llvm::TargetRegistry::targets()) {
#else
    for (auto it = llvm::TargetRegistry::begin(),
              ie = llvm::TargetRegistry::end();
         it != ie; ++it) {
      const llvm::Target &T = *it;
#endif
      if (arch == T.getName()) {
        target = &T;
        break;
      }
    }

    if (!target) {
      errorMsg = "invalid target architecture '" + arch +
                 "', see "
                 "-version for a list of supported targets.";
      return nullptr;
    }

    // Adjust the triple to match (if known), otherwise stick with the
    // given triple.
    llvm::Triple::ArchType Type = llvm::Triple::getArchTypeForLLVMName(arch);
    if (Type != llvm::Triple::UnknownArch) {
      triple.setArch(Type);
    }
  } else {
    std::string tempError;
    target = llvm::TargetRegistry::lookupTarget(triple.getTriple(), tempError);
    if (!target) {
      errorMsg = "unable to get target for '" + triple.getTriple() +
                 "', see -version and -mtriple.";
    }
  }

  return target;
}

llvm::TargetMachine *createTargetMachine(
    std::string targetTriple, std::string arch, std::string cpu,
    std::vector<std::string> attrs, ExplicitBitness::Type bitness,
    FloatABI::Type floatABI,
#if LDC_LLVM_VER >= 309
    llvm::Optional<llvm::Reloc::Model> relocModel,
#else
    llvm::Reloc::Model relocModel,
#endif
    llvm::CodeModel::Model codeModel, llvm::CodeGenOpt::Level codeGenOptLevel,
    bool noFramePointerElim, bool noLinkerStripDead) {
  // Determine target triple. If the user didn't explicitly specify one, use
  // the one set at LLVM configure time.
  llvm::Triple triple;
  if (targetTriple.empty()) {
    triple = llvm::Triple(llvm::sys::getDefaultTargetTriple());

    // We only support OSX, so darwin should really be macosx.
    if (triple.getOS() == llvm::Triple::Darwin) {
      triple.setOS(llvm::Triple::MacOSX);
    }

    // Handle -m32/-m64.
    if (sizeof(void *) == 4 && bitness == ExplicitBitness::M64) {
      triple = triple.get64BitArchVariant();
    } else if (sizeof(void *) == 8 && bitness == ExplicitBitness::M32) {
      triple = triple.get32BitArchVariant();
    }
  } else {
    triple = llvm::Triple(llvm::Triple::normalize(targetTriple));
  }

  // Look up the LLVM backend to use. This also updates triple with the
  // user-specified arch, if any.
  std::string errMsg;
  const llvm::Target *target = lookupTarget(arch, triple, errMsg);
  if (target == nullptr) {
    error(Loc(), "%s", errMsg.c_str());
    fatal();
  }

  // Package up features to be passed to target/subtarget.
  llvm::SubtargetFeatures features;
  features.getDefaultSubtargetFeatures(triple);
  if (cpu == "native") {
    llvm::StringMap<bool> hostFeatures;
    if (llvm::sys::getHostCPUFeatures(hostFeatures)) {
      for (const auto &hf : hostFeatures) {
        features.AddFeature(
            std::string(hf.second ? "+" : "-").append(hf.first()));
      }
    }
  }
#if LDC_LLVM_VER < 307
  if (triple.getArch() == llvm::Triple::mips ||
      triple.getArch() == llvm::Triple::mipsel ||
      triple.getArch() == llvm::Triple::mips64 ||
      triple.getArch() == llvm::Triple::mips64el) {
    addMipsABI(triple, attrs);
  }
#endif
  for (auto &attr : attrs) {
    features.AddFeature(attr);
  }

  // With an empty CPU string, LLVM will default to the host CPU, which is
  // usually not what we want (expected behavior from other compilers is
  // to default to "generic").
  cpu = getTargetCPU(cpu, triple);

  // cmpxchg16b is not available on old 64bit CPUs. Enable code generation
  // if the user did not make an explicit choice.
  if (cpu == "x86-64") {
    const char *cx16_plus = "+cx16";
    const char *cx16_minus = "-cx16";
    bool cx16 = false;
    for (auto &attr : attrs) {
      if (attr == cx16_plus || attr == cx16_minus) {
        cx16 = true;
      }
    }
    if (!cx16) {
      features.AddFeature(cx16_plus);
    }
  }

  if (Logger::enabled()) {
    Logger::println("Targeting '%s' (CPU '%s' with features '%s')",
                    triple.str().c_str(), cpu.c_str(),
                    features.getString().c_str());
  }

  // Handle cases where LLVM picks wrong default relocModel
#if LDC_LLVM_VER >= 309
  if (!relocModel.hasValue()) {
#else
  if (relocModel == llvm::Reloc::Default) {
#endif
    if (triple.isOSDarwin()) {
      // Darwin defaults to PIC (and as of 10.7.5/LLVM 3.1-3.3, TLS use leads
      // to crashes for non-PIC code). LLVM doesn't handle this.
      relocModel = llvm::Reloc::PIC_;
    } else if (triple.getEnvironment() == llvm::Triple::Android) {
      relocModel = llvm::Reloc::PIC_;
    } else {
      // ARM for other than Darwin or Android defaults to static
      switch (triple.getArch()) {
      default:
        break;
      case llvm::Triple::arm:
      case llvm::Triple::armeb:
      case llvm::Triple::thumb:
      case llvm::Triple::thumbeb:
        relocModel = llvm::Reloc::Static;
        break;
      }
    }
  }

  if (floatABI == FloatABI::Default) {
    switch (triple.getArch()) {
    default: // X86, ...
      floatABI = FloatABI::Hard;
      break;
    case llvm::Triple::arm:
    case llvm::Triple::thumb:
      floatABI = getARMFloatABI(triple, getLLVMArchSuffixForARM(cpu));
      break;
    }
  }

  llvm::TargetOptions targetOptions;
#if LDC_LLVM_VER < 307
  targetOptions.NoFramePointerElim = noFramePointerElim;
#endif
#if LDC_LLVM_VER >= 307
  targetOptions.MCOptions.ABIName = getABI(triple);
#endif

  switch (floatABI) {
  default:
    llvm_unreachable("Floating point ABI type unknown.");
  case FloatABI::Soft:
#if LDC_LLVM_VER < 307
    targetOptions.UseSoftFloat = true;
#endif
    targetOptions.FloatABIType = llvm::FloatABI::Soft;
    break;
  case FloatABI::SoftFP:
#if LDC_LLVM_VER < 307
    targetOptions.UseSoftFloat = false;
#endif
    targetOptions.FloatABIType = llvm::FloatABI::Soft;
    break;
  case FloatABI::Hard:
#if LDC_LLVM_VER < 307
    targetOptions.UseSoftFloat = false;
#endif
    targetOptions.FloatABIType = llvm::FloatABI::Hard;
    break;
  }

  // Right now, we only support linker-level dead code elimination on Linux
  // using the GNU toolchain (based on ld's --gc-sections flag). The Apple ld
  // on OS X supports a similar flag (-dead_strip) that doesn't require
  // emitting the symbols into different sections. The MinGW ld doesn't seem
  // to support --gc-sections at all, and FreeBSD needs more investigation.
  if (!noLinkerStripDead && (triple.getOS() == llvm::Triple::Linux ||
                             triple.getOS() == llvm::Triple::Win32)) {
    targetOptions.FunctionSections = true;
    targetOptions.DataSections = true;
  }

  return target->createTargetMachine(triple.str(), cpu, features.getString(),
                                     targetOptions, relocModel, codeModel,
                                     codeGenOptLevel);
}