| // Copyright 2022 The Abseil Authors. |
| // |
| // 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 |
| // |
| // https://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. |
| |
| // Hardware accelerated CRC32 computation on Intel and ARM architecture. |
| |
| #include <cstddef> |
| #include <cstdint> |
| #include <memory> |
| #include <vector> |
| |
| #include "absl/base/attributes.h" |
| #include "absl/base/config.h" |
| #include "absl/base/internal/endian.h" |
| #include "absl/base/prefetch.h" |
| #include "absl/crc/internal/cpu_detect.h" |
| #include "absl/crc/internal/crc32_x86_arm_combined_simd.h" |
| #include "absl/crc/internal/crc_internal.h" |
| #include "absl/memory/memory.h" |
| #include "absl/numeric/bits.h" |
| |
| #if defined(ABSL_CRC_INTERNAL_HAVE_ARM_SIMD) || \ |
| defined(ABSL_CRC_INTERNAL_HAVE_X86_SIMD) |
| #define ABSL_INTERNAL_CAN_USE_SIMD_CRC32C |
| #endif |
| |
| namespace absl { |
| ABSL_NAMESPACE_BEGIN |
| namespace crc_internal { |
| |
| #if defined(ABSL_INTERNAL_CAN_USE_SIMD_CRC32C) |
| |
| // Implementation details not exported outside of file |
| namespace { |
| |
| // Some machines have CRC acceleration hardware. |
| // We can do a faster version of Extend() on such machines. |
| class CRC32AcceleratedX86ARMCombined : public CRC32 { |
| public: |
| CRC32AcceleratedX86ARMCombined() {} |
| ~CRC32AcceleratedX86ARMCombined() override {} |
| void ExtendByZeroes(uint32_t* crc, size_t length) const override; |
| uint32_t ComputeZeroConstant(size_t length) const; |
| |
| private: |
| CRC32AcceleratedX86ARMCombined(const CRC32AcceleratedX86ARMCombined&) = |
| delete; |
| CRC32AcceleratedX86ARMCombined& operator=( |
| const CRC32AcceleratedX86ARMCombined&) = delete; |
| }; |
| |
| // Constants for switching between algorithms. |
| // Chosen by comparing speed at different powers of 2. |
| constexpr size_t kSmallCutoff = 256; |
| constexpr size_t kMediumCutoff = 2048; |
| |
| #define ABSL_INTERNAL_STEP1(crc) \ |
| do { \ |
| crc = CRC32_u8(static_cast<uint32_t>(crc), *p++); \ |
| } while (0) |
| #define ABSL_INTERNAL_STEP2(crc) \ |
| do { \ |
| crc = \ |
| CRC32_u16(static_cast<uint32_t>(crc), absl::little_endian::Load16(p)); \ |
| p += 2; \ |
| } while (0) |
| #define ABSL_INTERNAL_STEP4(crc) \ |
| do { \ |
| crc = \ |
| CRC32_u32(static_cast<uint32_t>(crc), absl::little_endian::Load32(p)); \ |
| p += 4; \ |
| } while (0) |
| #define ABSL_INTERNAL_STEP8(crc, data) \ |
| do { \ |
| crc = CRC32_u64(static_cast<uint32_t>(crc), \ |
| absl::little_endian::Load64(data)); \ |
| data += 8; \ |
| } while (0) |
| #define ABSL_INTERNAL_STEP8BY2(crc0, crc1, p0, p1) \ |
| do { \ |
| ABSL_INTERNAL_STEP8(crc0, p0); \ |
| ABSL_INTERNAL_STEP8(crc1, p1); \ |
| } while (0) |
| #define ABSL_INTERNAL_STEP8BY3(crc0, crc1, crc2, p0, p1, p2) \ |
| do { \ |
| ABSL_INTERNAL_STEP8(crc0, p0); \ |
| ABSL_INTERNAL_STEP8(crc1, p1); \ |
| ABSL_INTERNAL_STEP8(crc2, p2); \ |
| } while (0) |
| |
| namespace { |
| |
| uint32_t multiply(uint32_t a, uint32_t b) { |
| V128 power = V128_From64WithZeroFill(a); |
| V128 crc = V128_From64WithZeroFill(b); |
| V128 res = V128_PMulLow(power, crc); |
| |
| // Combine crc values. |
| // |
| // Adding res to itself is equivalent to multiplying by 2, |
| // or shifting left by 1. Addition is used as not all compilers |
| // are able to generate optimal code without this hint. |
| // https://godbolt.org/z/rr3fMnf39 |
| res = V128_Add64(res, res); |
| return static_cast<uint32_t>(V128_Extract32<1>(res)) ^ |
| CRC32_u32(0, static_cast<uint32_t>(V128_Low64(res))); |
| } |
| |
| // Powers of crc32c polynomial, for faster ExtendByZeros. |
| // Verified against folly: |
| // folly/hash/detail/Crc32CombineDetail.cpp |
| constexpr uint32_t kCRC32CPowers[] = { |
| 0x82f63b78, 0x6ea2d55c, 0x18b8ea18, 0x510ac59a, 0xb82be955, 0xb8fdb1e7, |
| 0x88e56f72, 0x74c360a4, 0xe4172b16, 0x0d65762a, 0x35d73a62, 0x28461564, |
| 0xbf455269, 0xe2ea32dc, 0xfe7740e6, 0xf946610b, 0x3c204f8f, 0x538586e3, |
| 0x59726915, 0x734d5309, 0xbc1ac763, 0x7d0722cc, 0xd289cabe, 0xe94ca9bc, |
| 0x05b74f3f, 0xa51e1f42, 0x40000000, 0x20000000, 0x08000000, 0x00800000, |
| 0x00008000, 0x82f63b78, 0x6ea2d55c, 0x18b8ea18, 0x510ac59a, 0xb82be955, |
| 0xb8fdb1e7, 0x88e56f72, 0x74c360a4, 0xe4172b16, 0x0d65762a, 0x35d73a62, |
| 0x28461564, 0xbf455269, 0xe2ea32dc, 0xfe7740e6, 0xf946610b, 0x3c204f8f, |
| 0x538586e3, 0x59726915, 0x734d5309, 0xbc1ac763, 0x7d0722cc, 0xd289cabe, |
| 0xe94ca9bc, 0x05b74f3f, 0xa51e1f42, 0x40000000, 0x20000000, 0x08000000, |
| 0x00800000, 0x00008000, |
| }; |
| |
| } // namespace |
| |
| // Compute a magic constant, so that multiplying by it is the same as |
| // extending crc by length zeros. |
| uint32_t CRC32AcceleratedX86ARMCombined::ComputeZeroConstant( |
| size_t length) const { |
| // Lowest 2 bits are handled separately in ExtendByZeroes |
| length >>= 2; |
| |
| int index = absl::countr_zero(length); |
| uint32_t prev = kCRC32CPowers[index]; |
| length &= length - 1; |
| |
| while (length) { |
| // For each bit of length, extend by 2**n zeros. |
| index = absl::countr_zero(length); |
| prev = multiply(prev, kCRC32CPowers[index]); |
| length &= length - 1; |
| } |
| return prev; |
| } |
| |
| void CRC32AcceleratedX86ARMCombined::ExtendByZeroes(uint32_t* crc, |
| size_t length) const { |
| uint32_t val = *crc; |
| // Don't bother with multiplication for small length. |
| switch (length & 3) { |
| case 0: |
| break; |
| case 1: |
| val = CRC32_u8(val, 0); |
| break; |
| case 2: |
| val = CRC32_u16(val, 0); |
| break; |
| case 3: |
| val = CRC32_u8(val, 0); |
| val = CRC32_u16(val, 0); |
| break; |
| } |
| if (length > 3) { |
| val = multiply(val, ComputeZeroConstant(length)); |
| } |
| *crc = val; |
| } |
| |
| // Taken from Intel paper "Fast CRC Computation for iSCSI Polynomial Using CRC32 |
| // Instruction" |
| // https://www.intel.com/content/dam/www/public/us/en/documents/white-papers/crc-iscsi-polynomial-crc32-instruction-paper.pdf |
| // We only need every 4th value, because we unroll loop by 4. |
| constexpr uint64_t kClmulConstants[] = { |
| 0x09e4addf8, 0x0ba4fc28e, 0x00d3b6092, 0x09e4addf8, 0x0ab7aff2a, |
| 0x102f9b8a2, 0x0b9e02b86, 0x00d3b6092, 0x1bf2e8b8a, 0x18266e456, |
| 0x0d270f1a2, 0x0ab7aff2a, 0x11eef4f8e, 0x083348832, 0x0dd7e3b0c, |
| 0x0b9e02b86, 0x0271d9844, 0x1b331e26a, 0x06b749fb2, 0x1bf2e8b8a, |
| 0x0e6fc4e6a, 0x0ce7f39f4, 0x0d7a4825c, 0x0d270f1a2, 0x026f6a60a, |
| 0x12ed0daac, 0x068bce87a, 0x11eef4f8e, 0x1329d9f7e, 0x0b3e32c28, |
| 0x0170076fa, 0x0dd7e3b0c, 0x1fae1cc66, 0x010746f3c, 0x086d8e4d2, |
| 0x0271d9844, 0x0b3af077a, 0x093a5f730, 0x1d88abd4a, 0x06b749fb2, |
| 0x0c9c8b782, 0x0cec3662e, 0x1ddffc5d4, 0x0e6fc4e6a, 0x168763fa6, |
| 0x0b0cd4768, 0x19b1afbc4, 0x0d7a4825c, 0x123888b7a, 0x00167d312, |
| 0x133d7a042, 0x026f6a60a, 0x000bcf5f6, 0x19d34af3a, 0x1af900c24, |
| 0x068bce87a, 0x06d390dec, 0x16cba8aca, 0x1f16a3418, 0x1329d9f7e, |
| 0x19fb2a8b0, 0x02178513a, 0x1a0f717c4, 0x0170076fa, |
| }; |
| |
| enum class CutoffStrategy { |
| // Use 3 CRC streams to fold into 1. |
| Fold3, |
| // Unroll CRC instructions for 64 bytes. |
| Unroll64CRC, |
| }; |
| |
| // Base class for CRC32AcceleratedX86ARMCombinedMultipleStreams containing the |
| // methods and data that don't need the template arguments. |
| class CRC32AcceleratedX86ARMCombinedMultipleStreamsBase |
| : public CRC32AcceleratedX86ARMCombined { |
| protected: |
| // Update partialCRC with crc of 64 byte block. Calling FinalizePclmulStream |
| // would produce a single crc checksum, but it is expensive. PCLMULQDQ has a |
| // high latency, so we run 4 128-bit partial checksums that can be reduced to |
| // a single value by FinalizePclmulStream later. Computing crc for arbitrary |
| // polynomialas with PCLMULQDQ is described in Intel paper "Fast CRC |
| // Computation for Generic Polynomials Using PCLMULQDQ Instruction" |
| // https://www.intel.com/content/dam/www/public/us/en/documents/white-papers/fast-crc-computation-generic-polynomials-pclmulqdq-paper.pdf |
| // We are applying it to CRC32C polynomial. |
| ABSL_ATTRIBUTE_ALWAYS_INLINE void Process64BytesPclmul( |
| const uint8_t* p, V128* partialCRC) const { |
| V128 loopMultiplicands = V128_Load(reinterpret_cast<const V128*>(k1k2)); |
| |
| V128 partialCRC1 = partialCRC[0]; |
| V128 partialCRC2 = partialCRC[1]; |
| V128 partialCRC3 = partialCRC[2]; |
| V128 partialCRC4 = partialCRC[3]; |
| |
| V128 tmp1 = V128_PMulHi(partialCRC1, loopMultiplicands); |
| V128 tmp2 = V128_PMulHi(partialCRC2, loopMultiplicands); |
| V128 tmp3 = V128_PMulHi(partialCRC3, loopMultiplicands); |
| V128 tmp4 = V128_PMulHi(partialCRC4, loopMultiplicands); |
| V128 data1 = V128_LoadU(reinterpret_cast<const V128*>(p + 16 * 0)); |
| V128 data2 = V128_LoadU(reinterpret_cast<const V128*>(p + 16 * 1)); |
| V128 data3 = V128_LoadU(reinterpret_cast<const V128*>(p + 16 * 2)); |
| V128 data4 = V128_LoadU(reinterpret_cast<const V128*>(p + 16 * 3)); |
| partialCRC1 = V128_PMulLow(partialCRC1, loopMultiplicands); |
| partialCRC2 = V128_PMulLow(partialCRC2, loopMultiplicands); |
| partialCRC3 = V128_PMulLow(partialCRC3, loopMultiplicands); |
| partialCRC4 = V128_PMulLow(partialCRC4, loopMultiplicands); |
| partialCRC1 = V128_Xor(tmp1, partialCRC1); |
| partialCRC2 = V128_Xor(tmp2, partialCRC2); |
| partialCRC3 = V128_Xor(tmp3, partialCRC3); |
| partialCRC4 = V128_Xor(tmp4, partialCRC4); |
| partialCRC1 = V128_Xor(partialCRC1, data1); |
| partialCRC2 = V128_Xor(partialCRC2, data2); |
| partialCRC3 = V128_Xor(partialCRC3, data3); |
| partialCRC4 = V128_Xor(partialCRC4, data4); |
| partialCRC[0] = partialCRC1; |
| partialCRC[1] = partialCRC2; |
| partialCRC[2] = partialCRC3; |
| partialCRC[3] = partialCRC4; |
| } |
| |
| // Reduce partialCRC produced by Process64BytesPclmul into a single value, |
| // that represents crc checksum of all the processed bytes. |
| ABSL_ATTRIBUTE_ALWAYS_INLINE uint64_t |
| FinalizePclmulStream(V128* partialCRC) const { |
| V128 partialCRC1 = partialCRC[0]; |
| V128 partialCRC2 = partialCRC[1]; |
| V128 partialCRC3 = partialCRC[2]; |
| V128 partialCRC4 = partialCRC[3]; |
| |
| // Combine 4 vectors of partial crc into a single vector. |
| V128 reductionMultiplicands = |
| V128_Load(reinterpret_cast<const V128*>(k5k6)); |
| |
| V128 low = V128_PMulLow(reductionMultiplicands, partialCRC1); |
| V128 high = V128_PMulHi(reductionMultiplicands, partialCRC1); |
| |
| partialCRC1 = V128_Xor(low, high); |
| partialCRC1 = V128_Xor(partialCRC1, partialCRC2); |
| |
| low = V128_PMulLow(reductionMultiplicands, partialCRC3); |
| high = V128_PMulHi(reductionMultiplicands, partialCRC3); |
| |
| partialCRC3 = V128_Xor(low, high); |
| partialCRC3 = V128_Xor(partialCRC3, partialCRC4); |
| |
| reductionMultiplicands = V128_Load(reinterpret_cast<const V128*>(k3k4)); |
| |
| low = V128_PMulLow(reductionMultiplicands, partialCRC1); |
| high = V128_PMulHi(reductionMultiplicands, partialCRC1); |
| V128 fullCRC = V128_Xor(low, high); |
| fullCRC = V128_Xor(fullCRC, partialCRC3); |
| |
| // Reduce fullCRC into scalar value. |
| reductionMultiplicands = V128_Load(reinterpret_cast<const V128*>(k5k6)); |
| |
| V128 mask = V128_Load(reinterpret_cast<const V128*>(kMask)); |
| |
| V128 tmp = V128_PMul01(reductionMultiplicands, fullCRC); |
| fullCRC = V128_ShiftRight<8>(fullCRC); |
| fullCRC = V128_Xor(fullCRC, tmp); |
| |
| reductionMultiplicands = V128_Load(reinterpret_cast<const V128*>(k7k0)); |
| |
| tmp = V128_ShiftRight<4>(fullCRC); |
| fullCRC = V128_And(fullCRC, mask); |
| fullCRC = V128_PMulLow(reductionMultiplicands, fullCRC); |
| fullCRC = V128_Xor(tmp, fullCRC); |
| |
| reductionMultiplicands = V128_Load(reinterpret_cast<const V128*>(kPoly)); |
| |
| tmp = V128_And(fullCRC, mask); |
| tmp = V128_PMul01(reductionMultiplicands, tmp); |
| tmp = V128_And(tmp, mask); |
| tmp = V128_PMulLow(reductionMultiplicands, tmp); |
| |
| fullCRC = V128_Xor(tmp, fullCRC); |
| |
| return static_cast<uint64_t>(V128_Extract32<1>(fullCRC)); |
| } |
| |
| // Update crc with 64 bytes of data from p. |
| ABSL_ATTRIBUTE_ALWAYS_INLINE uint64_t Process64BytesCRC(const uint8_t* p, |
| uint64_t crc) const { |
| for (int i = 0; i < 8; i++) { |
| crc = |
| CRC32_u64(static_cast<uint32_t>(crc), absl::little_endian::Load64(p)); |
| p += 8; |
| } |
| return crc; |
| } |
| |
| // Generated by crc32c_x86_test --crc32c_generate_constants=true |
| // and verified against constants in linux kernel for S390: |
| // https://github.com/torvalds/linux/blob/master/arch/s390/crypto/crc32le-vx.S |
| alignas(16) static constexpr uint64_t k1k2[2] = {0x0740eef02, 0x09e4addf8}; |
| alignas(16) static constexpr uint64_t k3k4[2] = {0x1384aa63a, 0x0ba4fc28e}; |
| alignas(16) static constexpr uint64_t k5k6[2] = {0x0f20c0dfe, 0x14cd00bd6}; |
| alignas(16) static constexpr uint64_t k7k0[2] = {0x0dd45aab8, 0x000000000}; |
| alignas(16) static constexpr uint64_t kPoly[2] = {0x105ec76f0, 0x0dea713f1}; |
| alignas(16) static constexpr uint32_t kMask[4] = {~0u, 0u, ~0u, 0u}; |
| |
| // Medium runs of bytes are broken into groups of kGroupsSmall blocks of same |
| // size. Each group is CRCed in parallel then combined at the end of the |
| // block. |
| static constexpr size_t kGroupsSmall = 3; |
| // For large runs we use up to kMaxStreams blocks computed with CRC |
| // instruction, and up to kMaxStreams blocks computed with PCLMULQDQ, which |
| // are combined in the end. |
| static constexpr size_t kMaxStreams = 3; |
| }; |
| |
| #ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL |
| alignas(16) constexpr uint64_t |
| CRC32AcceleratedX86ARMCombinedMultipleStreamsBase::k1k2[2]; |
| alignas(16) constexpr uint64_t |
| CRC32AcceleratedX86ARMCombinedMultipleStreamsBase::k3k4[2]; |
| alignas(16) constexpr uint64_t |
| CRC32AcceleratedX86ARMCombinedMultipleStreamsBase::k5k6[2]; |
| alignas(16) constexpr uint64_t |
| CRC32AcceleratedX86ARMCombinedMultipleStreamsBase::k7k0[2]; |
| alignas(16) constexpr uint64_t |
| CRC32AcceleratedX86ARMCombinedMultipleStreamsBase::kPoly[2]; |
| alignas(16) constexpr uint32_t |
| CRC32AcceleratedX86ARMCombinedMultipleStreamsBase::kMask[4]; |
| constexpr size_t |
| CRC32AcceleratedX86ARMCombinedMultipleStreamsBase::kGroupsSmall; |
| constexpr size_t CRC32AcceleratedX86ARMCombinedMultipleStreamsBase::kMaxStreams; |
| #endif // ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL |
| |
| template <size_t num_crc_streams, size_t num_pclmul_streams, |
| CutoffStrategy strategy> |
| class CRC32AcceleratedX86ARMCombinedMultipleStreams |
| : public CRC32AcceleratedX86ARMCombinedMultipleStreamsBase { |
| ABSL_ATTRIBUTE_HOT |
| void Extend(uint32_t* crc, const void* bytes, size_t length) const override { |
| static_assert(num_crc_streams >= 1 && num_crc_streams <= kMaxStreams, |
| "Invalid number of crc streams"); |
| static_assert(num_pclmul_streams >= 0 && num_pclmul_streams <= kMaxStreams, |
| "Invalid number of pclmul streams"); |
| const uint8_t* p = static_cast<const uint8_t*>(bytes); |
| const uint8_t* e = p + length; |
| uint32_t l = *crc; |
| uint64_t l64; |
| |
| // We have dedicated instruction for 1,2,4 and 8 bytes. |
| if (length & 8) { |
| ABSL_INTERNAL_STEP8(l, p); |
| length &= ~size_t{8}; |
| } |
| if (length & 4) { |
| ABSL_INTERNAL_STEP4(l); |
| length &= ~size_t{4}; |
| } |
| if (length & 2) { |
| ABSL_INTERNAL_STEP2(l); |
| length &= ~size_t{2}; |
| } |
| if (length & 1) { |
| ABSL_INTERNAL_STEP1(l); |
| length &= ~size_t{1}; |
| } |
| if (length == 0) { |
| *crc = l; |
| return; |
| } |
| // length is now multiple of 16. |
| |
| // For small blocks just run simple loop, because cost of combining multiple |
| // streams is significant. |
| if (strategy != CutoffStrategy::Unroll64CRC) { |
| if (length < kSmallCutoff) { |
| while (length >= 16) { |
| ABSL_INTERNAL_STEP8(l, p); |
| ABSL_INTERNAL_STEP8(l, p); |
| length -= 16; |
| } |
| *crc = l; |
| return; |
| } |
| } |
| |
| // For medium blocks we run 3 crc streams and combine them as described in |
| // Intel paper above. Running 4th stream doesn't help, because crc |
| // instruction has latency 3 and throughput 1. |
| if (length < kMediumCutoff) { |
| l64 = l; |
| if (strategy == CutoffStrategy::Fold3) { |
| uint64_t l641 = 0; |
| uint64_t l642 = 0; |
| const size_t blockSize = 32; |
| size_t bs = static_cast<size_t>(e - p) / kGroupsSmall / blockSize; |
| const uint8_t* p1 = p + bs * blockSize; |
| const uint8_t* p2 = p1 + bs * blockSize; |
| |
| for (size_t i = 0; i + 1 < bs; ++i) { |
| ABSL_INTERNAL_STEP8BY3(l64, l641, l642, p, p1, p2); |
| ABSL_INTERNAL_STEP8BY3(l64, l641, l642, p, p1, p2); |
| ABSL_INTERNAL_STEP8BY3(l64, l641, l642, p, p1, p2); |
| ABSL_INTERNAL_STEP8BY3(l64, l641, l642, p, p1, p2); |
| PrefetchToLocalCache( |
| reinterpret_cast<const char*>(p + kPrefetchHorizonMedium)); |
| PrefetchToLocalCache( |
| reinterpret_cast<const char*>(p1 + kPrefetchHorizonMedium)); |
| PrefetchToLocalCache( |
| reinterpret_cast<const char*>(p2 + kPrefetchHorizonMedium)); |
| } |
| // Don't run crc on last 8 bytes. |
| ABSL_INTERNAL_STEP8BY3(l64, l641, l642, p, p1, p2); |
| ABSL_INTERNAL_STEP8BY3(l64, l641, l642, p, p1, p2); |
| ABSL_INTERNAL_STEP8BY3(l64, l641, l642, p, p1, p2); |
| ABSL_INTERNAL_STEP8BY2(l64, l641, p, p1); |
| |
| V128 magic = *(reinterpret_cast<const V128*>(kClmulConstants) + bs - 1); |
| |
| V128 tmp = V128_From64WithZeroFill(l64); |
| |
| V128 res1 = V128_PMulLow(tmp, magic); |
| |
| tmp = V128_From64WithZeroFill(l641); |
| |
| V128 res2 = V128_PMul10(tmp, magic); |
| V128 x = V128_Xor(res1, res2); |
| l64 = static_cast<uint64_t>(V128_Low64(x)) ^ |
| absl::little_endian::Load64(p2); |
| l64 = CRC32_u64(static_cast<uint32_t>(l642), l64); |
| |
| p = p2 + 8; |
| } else if (strategy == CutoffStrategy::Unroll64CRC) { |
| while ((e - p) >= 64) { |
| l64 = Process64BytesCRC(p, l64); |
| p += 64; |
| } |
| } |
| } else { |
| // There is a lot of data, we can ignore combine costs and run all |
| // requested streams (num_crc_streams + num_pclmul_streams), |
| // using prefetch. CRC and PCLMULQDQ use different cpu execution units, |
| // so on some cpus it makes sense to execute both of them for different |
| // streams. |
| |
| // Point x at first 8-byte aligned byte in string. |
| const uint8_t* x = RoundUp<8>(p); |
| // Process bytes until p is 8-byte aligned, if that isn't past the end. |
| while (p != x) { |
| ABSL_INTERNAL_STEP1(l); |
| } |
| |
| size_t bs = static_cast<size_t>(e - p) / |
| (num_crc_streams + num_pclmul_streams) / 64; |
| const uint8_t* crc_streams[kMaxStreams]; |
| const uint8_t* pclmul_streams[kMaxStreams]; |
| // We are guaranteed to have at least one crc stream. |
| crc_streams[0] = p; |
| for (size_t i = 1; i < num_crc_streams; i++) { |
| crc_streams[i] = crc_streams[i - 1] + bs * 64; |
| } |
| pclmul_streams[0] = crc_streams[num_crc_streams - 1] + bs * 64; |
| for (size_t i = 1; i < num_pclmul_streams; i++) { |
| pclmul_streams[i] = pclmul_streams[i - 1] + bs * 64; |
| } |
| |
| // Per stream crc sums. |
| uint64_t l64_crc[kMaxStreams] = {l}; |
| uint64_t l64_pclmul[kMaxStreams] = {0}; |
| |
| // Peel first iteration, because PCLMULQDQ stream, needs setup. |
| for (size_t i = 0; i < num_crc_streams; i++) { |
| l64_crc[i] = Process64BytesCRC(crc_streams[i], l64_crc[i]); |
| crc_streams[i] += 16 * 4; |
| } |
| |
| V128 partialCRC[kMaxStreams][4]; |
| for (size_t i = 0; i < num_pclmul_streams; i++) { |
| partialCRC[i][0] = V128_LoadU( |
| reinterpret_cast<const V128*>(pclmul_streams[i] + 16 * 0)); |
| partialCRC[i][1] = V128_LoadU( |
| reinterpret_cast<const V128*>(pclmul_streams[i] + 16 * 1)); |
| partialCRC[i][2] = V128_LoadU( |
| reinterpret_cast<const V128*>(pclmul_streams[i] + 16 * 2)); |
| partialCRC[i][3] = V128_LoadU( |
| reinterpret_cast<const V128*>(pclmul_streams[i] + 16 * 3)); |
| pclmul_streams[i] += 16 * 4; |
| } |
| |
| for (size_t i = 1; i < bs; i++) { |
| // Prefetch data for next iterations. |
| for (size_t j = 0; j < num_crc_streams; j++) { |
| PrefetchToLocalCache( |
| reinterpret_cast<const char*>(crc_streams[j] + kPrefetchHorizon)); |
| } |
| for (size_t j = 0; j < num_pclmul_streams; j++) { |
| PrefetchToLocalCache(reinterpret_cast<const char*>(pclmul_streams[j] + |
| kPrefetchHorizon)); |
| } |
| |
| // We process each stream in 64 byte blocks. This can be written as |
| // for (int i = 0; i < num_pclmul_streams; i++) { |
| // Process64BytesPclmul(pclmul_streams[i], partialCRC[i]); |
| // pclmul_streams[i] += 16 * 4; |
| // } |
| // for (int i = 0; i < num_crc_streams; i++) { |
| // l64_crc[i] = Process64BytesCRC(crc_streams[i], l64_crc[i]); |
| // crc_streams[i] += 16*4; |
| // } |
| // But unrolling and interleaving PCLMULQDQ and CRC blocks manually |
| // gives ~2% performance boost. |
| l64_crc[0] = Process64BytesCRC(crc_streams[0], l64_crc[0]); |
| crc_streams[0] += 16 * 4; |
| if (num_pclmul_streams > 0) { |
| Process64BytesPclmul(pclmul_streams[0], partialCRC[0]); |
| pclmul_streams[0] += 16 * 4; |
| } |
| if (num_crc_streams > 1) { |
| l64_crc[1] = Process64BytesCRC(crc_streams[1], l64_crc[1]); |
| crc_streams[1] += 16 * 4; |
| } |
| if (num_pclmul_streams > 1) { |
| Process64BytesPclmul(pclmul_streams[1], partialCRC[1]); |
| pclmul_streams[1] += 16 * 4; |
| } |
| if (num_crc_streams > 2) { |
| l64_crc[2] = Process64BytesCRC(crc_streams[2], l64_crc[2]); |
| crc_streams[2] += 16 * 4; |
| } |
| if (num_pclmul_streams > 2) { |
| Process64BytesPclmul(pclmul_streams[2], partialCRC[2]); |
| pclmul_streams[2] += 16 * 4; |
| } |
| } |
| |
| // PCLMULQDQ based streams require special final step; |
| // CRC based don't. |
| for (size_t i = 0; i < num_pclmul_streams; i++) { |
| l64_pclmul[i] = FinalizePclmulStream(partialCRC[i]); |
| } |
| |
| // Combine all streams into single result. |
| uint32_t magic = ComputeZeroConstant(bs * 64); |
| l64 = l64_crc[0]; |
| for (size_t i = 1; i < num_crc_streams; i++) { |
| l64 = multiply(static_cast<uint32_t>(l64), magic); |
| l64 ^= l64_crc[i]; |
| } |
| for (size_t i = 0; i < num_pclmul_streams; i++) { |
| l64 = multiply(static_cast<uint32_t>(l64), magic); |
| l64 ^= l64_pclmul[i]; |
| } |
| |
| // Update p. |
| if (num_pclmul_streams > 0) { |
| p = pclmul_streams[num_pclmul_streams - 1]; |
| } else { |
| p = crc_streams[num_crc_streams - 1]; |
| } |
| } |
| l = static_cast<uint32_t>(l64); |
| |
| while ((e - p) >= 16) { |
| ABSL_INTERNAL_STEP8(l, p); |
| ABSL_INTERNAL_STEP8(l, p); |
| } |
| // Process the last few bytes |
| while (p != e) { |
| ABSL_INTERNAL_STEP1(l); |
| } |
| |
| #undef ABSL_INTERNAL_STEP8BY3 |
| #undef ABSL_INTERNAL_STEP8BY2 |
| #undef ABSL_INTERNAL_STEP8 |
| #undef ABSL_INTERNAL_STEP4 |
| #undef ABSL_INTERNAL_STEP2 |
| #undef ABSL_INTERNAL_STEP1 |
| |
| *crc = l; |
| } |
| }; |
| |
| } // namespace |
| |
| // Intel processors with SSE4.2 have an instruction for one particular |
| // 32-bit CRC polynomial: crc32c |
| CRCImpl* TryNewCRC32AcceleratedX86ARMCombined() { |
| CpuType type = GetCpuType(); |
| switch (type) { |
| case CpuType::kIntelHaswell: |
| case CpuType::kAmdRome: |
| case CpuType::kAmdNaples: |
| case CpuType::kAmdMilan: |
| return new CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 3, 1, CutoffStrategy::Fold3>(); |
| // PCLMULQDQ is fast, use combined PCLMULQDQ + CRC implementation. |
| case CpuType::kIntelCascadelakeXeon: |
| case CpuType::kIntelSkylakeXeon: |
| case CpuType::kIntelBroadwell: |
| case CpuType::kIntelSkylake: |
| return new CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 3, 2, CutoffStrategy::Fold3>(); |
| // PCLMULQDQ is slow, don't use it. |
| case CpuType::kIntelIvybridge: |
| case CpuType::kIntelSandybridge: |
| case CpuType::kIntelWestmere: |
| return new CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 3, 0, CutoffStrategy::Fold3>(); |
| case CpuType::kArmNeoverseN1: |
| case CpuType::kArmNeoverseN2: |
| case CpuType::kArmNeoverseV1: |
| return new CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 1, 1, CutoffStrategy::Unroll64CRC>(); |
| case CpuType::kAmpereSiryn: |
| return new CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 3, 2, CutoffStrategy::Fold3>(); |
| case CpuType::kArmNeoverseV2: |
| return new CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 1, 2, CutoffStrategy::Unroll64CRC>(); |
| #if defined(__aarch64__) |
| default: |
| // Not all ARM processors support the needed instructions, so check here |
| // before trying to use an accelerated implementation. |
| if (SupportsArmCRC32PMULL()) { |
| return new CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 1, 1, CutoffStrategy::Unroll64CRC>(); |
| } else { |
| return nullptr; |
| } |
| #else |
| default: |
| // Something else, play it safe and assume slow PCLMULQDQ. |
| return new CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 3, 0, CutoffStrategy::Fold3>(); |
| #endif |
| } |
| } |
| |
| std::vector<std::unique_ptr<CRCImpl>> NewCRC32AcceleratedX86ARMCombinedAll() { |
| auto ret = std::vector<std::unique_ptr<CRCImpl>>(); |
| ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 1, 0, CutoffStrategy::Fold3>>()); |
| ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 1, 1, CutoffStrategy::Fold3>>()); |
| ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 1, 2, CutoffStrategy::Fold3>>()); |
| ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 1, 3, CutoffStrategy::Fold3>>()); |
| ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 2, 0, CutoffStrategy::Fold3>>()); |
| ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 2, 1, CutoffStrategy::Fold3>>()); |
| ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 2, 2, CutoffStrategy::Fold3>>()); |
| ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 2, 3, CutoffStrategy::Fold3>>()); |
| ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 3, 0, CutoffStrategy::Fold3>>()); |
| ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 3, 1, CutoffStrategy::Fold3>>()); |
| ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 3, 2, CutoffStrategy::Fold3>>()); |
| ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 3, 3, CutoffStrategy::Fold3>>()); |
| ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 1, 0, CutoffStrategy::Unroll64CRC>>()); |
| ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 1, 1, CutoffStrategy::Unroll64CRC>>()); |
| ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 1, 2, CutoffStrategy::Unroll64CRC>>()); |
| ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 1, 3, CutoffStrategy::Unroll64CRC>>()); |
| ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 2, 0, CutoffStrategy::Unroll64CRC>>()); |
| ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 2, 1, CutoffStrategy::Unroll64CRC>>()); |
| ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 2, 2, CutoffStrategy::Unroll64CRC>>()); |
| ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 2, 3, CutoffStrategy::Unroll64CRC>>()); |
| ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 3, 0, CutoffStrategy::Unroll64CRC>>()); |
| ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 3, 1, CutoffStrategy::Unroll64CRC>>()); |
| ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 3, 2, CutoffStrategy::Unroll64CRC>>()); |
| ret.push_back(absl::make_unique<CRC32AcceleratedX86ARMCombinedMultipleStreams< |
| 3, 3, CutoffStrategy::Unroll64CRC>>()); |
| |
| return ret; |
| } |
| |
| #else // !ABSL_INTERNAL_CAN_USE_SIMD_CRC32C |
| |
| std::vector<std::unique_ptr<CRCImpl>> NewCRC32AcceleratedX86ARMCombinedAll() { |
| return std::vector<std::unique_ptr<CRCImpl>>(); |
| } |
| |
| // no hardware acceleration available |
| CRCImpl* TryNewCRC32AcceleratedX86ARMCombined() { return nullptr; } |
| |
| #endif |
| |
| } // namespace crc_internal |
| ABSL_NAMESPACE_END |
| } // namespace absl |
