// Copyright 2019 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "hwy/targets.h"

#include <stdarg.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>

#include <atomic>

#include "hwy/base.h"

#if HWY_IS_ASAN || HWY_IS_MSAN || HWY_IS_TSAN
#include "sanitizer/common_interface_defs.h"  // __sanitizer_print_stack_trace
#endif

#include <stdlib.h>  // abort / exit

#if HWY_ARCH_X86
#include <xmmintrin.h>
#if HWY_COMPILER_MSVC
#include <intrin.h>
#else  // !HWY_COMPILER_MSVC
#include <cpuid.h>
#endif  // HWY_COMPILER_MSVC
#endif  // HWY_ARCH_X86

namespace hwy {
namespace {

#if HWY_ARCH_X86

HWY_INLINE bool IsBitSet(const uint32_t reg, const int index) {
  return (reg & (1U << index)) != 0;
}

// Calls CPUID instruction with eax=level and ecx=count and returns the result
// in abcd array where abcd = {eax, ebx, ecx, edx} (hence the name abcd).
HWY_INLINE void Cpuid(const uint32_t level, const uint32_t count,
                      uint32_t* HWY_RESTRICT abcd) {
#if HWY_COMPILER_MSVC
  int regs[4];
  __cpuidex(regs, level, count);
  for (int i = 0; i < 4; ++i) {
    abcd[i] = regs[i];
  }
#else  // HWY_COMPILER_MSVC
  uint32_t a;
  uint32_t b;
  uint32_t c;
  uint32_t d;
  __cpuid_count(level, count, a, b, c, d);
  abcd[0] = a;
  abcd[1] = b;
  abcd[2] = c;
  abcd[3] = d;
#endif  // HWY_COMPILER_MSVC
}

// Returns the lower 32 bits of extended control register 0.
// Requires CPU support for "OSXSAVE" (see below).
uint32_t ReadXCR0() {
#if HWY_COMPILER_MSVC
  return static_cast<uint32_t>(_xgetbv(0));
#else  // HWY_COMPILER_MSVC
  uint32_t xcr0, xcr0_high;
  const uint32_t index = 0;
  asm volatile(".byte 0x0F, 0x01, 0xD0"
               : "=a"(xcr0), "=d"(xcr0_high)
               : "c"(index));
  return xcr0;
#endif  // HWY_COMPILER_MSVC
}

#endif  // HWY_ARCH_X86

// Not function-local => no compiler-generated locking.
std::atomic<uint32_t> supported_{0};  // Not yet initialized

// When running tests, this value can be set to the mocked supported targets
// mask. Only written to from a single thread before the test starts.
uint32_t supported_targets_for_test_ = 0;

// Mask of targets disabled at runtime with DisableTargets.
uint32_t supported_mask_{LimitsMax<uint32_t>()};

#if HWY_ARCH_X86
// Arbritrary bit indices indicating which instruction set extensions are
// supported. Use enum to ensure values are distinct.
enum class FeatureIndex : uint32_t {
  kSSE = 0,
  kSSE2,
  kSSE3,
  kSSSE3,

  kSSE41,
  kSSE42,
  kCLMUL,
  kAES,

  kAVX,
  kAVX2,
  kF16C,
  kFMA,
  kLZCNT,
  kBMI,
  kBMI2,

  kAVX512F,
  kAVX512VL,
  kAVX512DQ,
  kAVX512BW,

  kVNNI,
  kVPCLMULQDQ,
  kVBMI2,
  kVAES,
  kPOPCNTDQ,
  kBITALG,

  kSentinel
};
static_assert(static_cast<size_t>(FeatureIndex::kSentinel) < 64,
              "Too many bits for u64");

HWY_INLINE constexpr uint64_t Bit(FeatureIndex index) {
  return 1ull << static_cast<size_t>(index);
}

constexpr uint64_t kGroupSSSE3 =
    Bit(FeatureIndex::kSSE) | Bit(FeatureIndex::kSSE2) |
    Bit(FeatureIndex::kSSE3) | Bit(FeatureIndex::kSSSE3);

constexpr uint64_t kGroupSSE4 =
    Bit(FeatureIndex::kSSE41) | Bit(FeatureIndex::kSSE42) |
    Bit(FeatureIndex::kCLMUL) | Bit(FeatureIndex::kAES) | kGroupSSSE3;

// We normally assume BMI/BMI2/FMA are available if AVX2 is. This allows us to
// use BZHI and (compiler-generated) MULX. However, VirtualBox lacks them
// [https://www.virtualbox.org/ticket/15471]. Thus we provide the option of
// avoiding using and requiring these so AVX2 can still be used.
#ifdef HWY_DISABLE_BMI2_FMA
constexpr uint64_t kGroupBMI2_FMA = 0;
#else
constexpr uint64_t kGroupBMI2_FMA = Bit(FeatureIndex::kBMI) |
                                    Bit(FeatureIndex::kBMI2) |
                                    Bit(FeatureIndex::kFMA);
#endif

#ifdef HWY_DISABLE_F16C
constexpr uint64_t kGroupF16C = 0;
#else
constexpr uint64_t kGroupF16C = Bit(FeatureIndex::kF16C);
#endif

constexpr uint64_t kGroupAVX2 =
    Bit(FeatureIndex::kAVX) | Bit(FeatureIndex::kAVX2) |
    Bit(FeatureIndex::kLZCNT) | kGroupBMI2_FMA | kGroupF16C | kGroupSSE4;

constexpr uint64_t kGroupAVX3 =
    Bit(FeatureIndex::kAVX512F) | Bit(FeatureIndex::kAVX512VL) |
    Bit(FeatureIndex::kAVX512DQ) | Bit(FeatureIndex::kAVX512BW) | kGroupAVX2;

constexpr uint64_t kGroupAVX3_DL =
    Bit(FeatureIndex::kVNNI) | Bit(FeatureIndex::kVPCLMULQDQ) |
    Bit(FeatureIndex::kVBMI2) | Bit(FeatureIndex::kVAES) |
    Bit(FeatureIndex::kPOPCNTDQ) | Bit(FeatureIndex::kBITALG) | kGroupAVX3;

#endif  // HWY_ARCH_X86

}  // namespace

HWY_NORETURN void HWY_FORMAT(3, 4)
    Abort(const char* file, int line, const char* format, ...) {
  char buf[2000];
  va_list args;
  va_start(args, format);
  vsnprintf(buf, sizeof(buf), format, args);
  va_end(args);

  fprintf(stderr, "Abort at %s:%d: %s\n", file, line, buf);

// If compiled with any sanitizer, they can also print a stack trace.
#if HWY_IS_ASAN || HWY_IS_MSAN || HWY_IS_TSAN
  __sanitizer_print_stack_trace();
#endif  // HWY_IS_*
  fflush(stderr);

// Now terminate the program:
#if HWY_ARCH_RVV
  exit(1);  // trap/abort just freeze Spike.
#elif HWY_IS_DEBUG_BUILD && !HWY_COMPILER_MSVC
  // Facilitates breaking into a debugger, but don't use this in non-debug
  // builds because it looks like "illegal instruction", which is misleading.
  __builtin_trap();
#else
  abort();  // Compile error without this due to HWY_NORETURN.
#endif
}

void DisableTargets(uint32_t disabled_targets) {
  supported_mask_ = ~(disabled_targets & ~uint32_t(HWY_ENABLED_BASELINE));
  // We can call Update() here to initialize the mask but that will trigger a
  // call to SupportedTargets() which we use in tests to tell whether any of the
  // highway dynamic dispatch functions were used.
  GetChosenTarget().DeInit();
}

void SetSupportedTargetsForTest(uint32_t targets) {
  // Reset the cached supported_ value to 0 to force a re-evaluation in the
  // next call to SupportedTargets() which will use the mocked value set here
  // if not zero.
  supported_.store(0, std::memory_order_release);
  supported_targets_for_test_ = targets;
  GetChosenTarget().DeInit();
}

bool SupportedTargetsCalledForTest() {
  return supported_.load(std::memory_order_acquire) != 0;
}

uint32_t SupportedTargets() {
  uint32_t bits = supported_.load(std::memory_order_acquire);
  // Already initialized?
  if (HWY_LIKELY(bits != 0)) {
    return bits & supported_mask_;
  }

  // When running tests, this allows to mock the current supported targets.
  if (HWY_UNLIKELY(supported_targets_for_test_ != 0)) {
    // Store the value to signal that this was used.
    supported_.store(supported_targets_for_test_, std::memory_order_release);
    return supported_targets_for_test_ & supported_mask_;
  }

  bits = HWY_SCALAR;

#if HWY_ARCH_X86
  bool has_osxsave = false;
  {  // ensures we do not accidentally use flags outside this block
    uint64_t flags = 0;
    uint32_t abcd[4];

    Cpuid(0, 0, abcd);
    const uint32_t max_level = abcd[0];

    // Standard feature flags
    Cpuid(1, 0, abcd);
    flags |= IsBitSet(abcd[3], 25) ? Bit(FeatureIndex::kSSE) : 0;
    flags |= IsBitSet(abcd[3], 26) ? Bit(FeatureIndex::kSSE2) : 0;
    flags |= IsBitSet(abcd[2], 0) ? Bit(FeatureIndex::kSSE3) : 0;
    flags |= IsBitSet(abcd[2], 1) ? Bit(FeatureIndex::kCLMUL) : 0;
    flags |= IsBitSet(abcd[2], 9) ? Bit(FeatureIndex::kSSSE3) : 0;
    flags |= IsBitSet(abcd[2], 12) ? Bit(FeatureIndex::kFMA) : 0;
    flags |= IsBitSet(abcd[2], 19) ? Bit(FeatureIndex::kSSE41) : 0;
    flags |= IsBitSet(abcd[2], 20) ? Bit(FeatureIndex::kSSE42) : 0;
    flags |= IsBitSet(abcd[2], 25) ? Bit(FeatureIndex::kAES) : 0;
    flags |= IsBitSet(abcd[2], 28) ? Bit(FeatureIndex::kAVX) : 0;
    flags |= IsBitSet(abcd[2], 29) ? Bit(FeatureIndex::kF16C) : 0;
    has_osxsave = IsBitSet(abcd[2], 27);

    // Extended feature flags
    Cpuid(0x80000001U, 0, abcd);
    flags |= IsBitSet(abcd[2], 5) ? Bit(FeatureIndex::kLZCNT) : 0;

    // Extended features
    if (max_level >= 7) {
      Cpuid(7, 0, abcd);
      flags |= IsBitSet(abcd[1], 3) ? Bit(FeatureIndex::kBMI) : 0;
      flags |= IsBitSet(abcd[1], 5) ? Bit(FeatureIndex::kAVX2) : 0;
      flags |= IsBitSet(abcd[1], 8) ? Bit(FeatureIndex::kBMI2) : 0;

      flags |= IsBitSet(abcd[1], 16) ? Bit(FeatureIndex::kAVX512F) : 0;
      flags |= IsBitSet(abcd[1], 17) ? Bit(FeatureIndex::kAVX512DQ) : 0;
      flags |= IsBitSet(abcd[1], 30) ? Bit(FeatureIndex::kAVX512BW) : 0;
      flags |= IsBitSet(abcd[1], 31) ? Bit(FeatureIndex::kAVX512VL) : 0;

      flags |= IsBitSet(abcd[2], 6) ? Bit(FeatureIndex::kVBMI2) : 0;
      flags |= IsBitSet(abcd[2], 9) ? Bit(FeatureIndex::kVAES) : 0;
      flags |= IsBitSet(abcd[2], 10) ? Bit(FeatureIndex::kVPCLMULQDQ) : 0;
      flags |= IsBitSet(abcd[2], 11) ? Bit(FeatureIndex::kVNNI) : 0;
      flags |= IsBitSet(abcd[2], 12) ? Bit(FeatureIndex::kBITALG) : 0;
      flags |= IsBitSet(abcd[2], 14) ? Bit(FeatureIndex::kPOPCNTDQ) : 0;
    }

    // Set target bit(s) if all their group's flags are all set.
    if ((flags & kGroupAVX3_DL) == kGroupAVX3_DL) {
      bits |= HWY_AVX3_DL;
    }
    if ((flags & kGroupAVX3) == kGroupAVX3) {
      bits |= HWY_AVX3;
    }
    if ((flags & kGroupAVX2) == kGroupAVX2) {
      bits |= HWY_AVX2;
    }
    if ((flags & kGroupSSE4) == kGroupSSE4) {
      bits |= HWY_SSE4;
    }
    if ((flags & kGroupSSSE3) == kGroupSSSE3) {
      bits |= HWY_SSSE3;
    }
  }

  // Clear bits if the OS does not support XSAVE - otherwise, registers
  // are not preserved across context switches.
  if (has_osxsave) {
    const uint32_t xcr0 = ReadXCR0();
    // XMM
    if (!IsBitSet(xcr0, 1)) {
      bits &=
          ~uint32_t(HWY_SSSE3 | HWY_SSE4 | HWY_AVX2 | HWY_AVX3 | HWY_AVX3_DL);
    }
    // YMM
    if (!IsBitSet(xcr0, 2)) {
      bits &= ~uint32_t(HWY_AVX2 | HWY_AVX3 | HWY_AVX3_DL);
    }
    // ZMM + opmask
    if ((xcr0 & 0x70) != 0x70) {
      bits &= ~uint32_t(HWY_AVX3 | HWY_AVX3_DL);
    }
  }

#else
  // TODO(janwas): detect for other platforms
  bits = HWY_ENABLED_BASELINE;
#endif  // HWY_ARCH_X86

  if ((bits & HWY_ENABLED_BASELINE) != HWY_ENABLED_BASELINE) {
    fprintf(stderr, "WARNING: CPU supports %zx but software requires %x\n",
            size_t(bits), HWY_ENABLED_BASELINE);
  }

  supported_.store(bits, std::memory_order_release);
  return bits & supported_mask_;
}

HWY_DLLEXPORT ChosenTarget& GetChosenTarget() {
  static ChosenTarget chosen_target;
  return chosen_target;
}

void ChosenTarget::Update() {
  // The supported variable contains the current CPU supported targets shifted
  // to the location expected by the ChosenTarget mask. We enabled SCALAR
  // regardless of whether it was compiled since it is also used as the
  // fallback mechanism to the baseline target.
  uint32_t supported = HWY_CHOSEN_TARGET_SHIFT(hwy::SupportedTargets()) |
                       HWY_CHOSEN_TARGET_MASK_SCALAR;
  mask_.store(supported);
}

}  // namespace hwy