// delta-plus-1 is implemented, and only 32-bit docids are tested),
// but aim to be more portable and (ideally) easier-to-understand.
// In particular, they will compile on x86 without SSE4.1 or AVX support.
+// Unlike the reference code, only GCC and GCC-compatible compilers
+// (e.g. Clang) are supported.
//
// The main reference is https://michael.stapelberg.ch/posts/2019-02-05-turbopfor-analysis/,
// although some implementation details have been worked out by studying the
// TurboPFor code.
-
-#include <assert.h>
-#include <endian.h>
-#include <stdint.h>
-#include <string.h>
-#include <limits.h>
-
-#include <algorithm>
-
-#if defined(__i386__) || defined(__x86_64__)
-#define COULD_HAVE_SSE2
-#include <immintrin.h>
-#endif
-
-// Forward declarations to declare to the template code below that they exist.
-// (These must seemingly be non-templates for function multiversioning to work.)
-__attribute__((target("default")))
-const unsigned char *decode_for_interleaved_128_32(const unsigned char *in, uint32_t *out);
-__attribute__((target("default")))
-const unsigned char *decode_pfor_bitmap_interleaved_128_32(const unsigned char *in, uint32_t *out);
-__attribute__((target("default")))
-const unsigned char *decode_pfor_vb_interleaved_128_32(const unsigned char *in, uint32_t *out);
-
-#ifdef COULD_HAVE_SSE2
-__attribute__((target("sse2")))
-const unsigned char *decode_for_interleaved_128_32(const unsigned char *in, uint32_t *out);
-__attribute__((target("sse2")))
-const unsigned char *decode_pfor_bitmap_interleaved_128_32(const unsigned char *in, uint32_t *out);
-__attribute__((target("sse2")))
-const unsigned char *decode_pfor_vb_interleaved_128_32(const unsigned char *in, uint32_t *out);
-#endif
-
-constexpr uint32_t mask_for_bits(unsigned bit_width)
-{
- if (bit_width == 32) {
- return 0xFFFFFFFF;
- } else {
- return (1U << bit_width) - 1;
- }
-}
-
-template<class Docid>
-Docid read_le(const void *in)
-{
- Docid val;
- memcpy(&val, in, sizeof(val));
- if constexpr (sizeof(Docid) == 8) {
- return le64toh(val);
- } else if constexpr (sizeof(Docid) == 4) {
- return le32toh(val);
- } else if constexpr (sizeof(Docid) == 2) {
- return le16toh(val);
- } else if constexpr (sizeof(Docid) == 1) {
- return val;
- } else {
- assert(false);
- }
-}
-
-// Reads a single value with an encoding that looks a bit like PrefixVarint.
-// It's unclear why this doesn't use the varbyte encoding.
-template<class Docid>
-const unsigned char *read_baseval(const unsigned char *in, Docid *out)
-{
- //fprintf(stderr, "baseval: 0x%02x 0x%02x 0x%02x 0x%02x\n", in[0], in[1], in[2], in[3]);
- if (*in < 128) {
- *out = *in;
- return in + 1;
- } else if (*in < 192) {
- *out = ((uint32_t(in[0]) << 8) | uint32_t(in[1])) & 0x3fff;
- return in + 2;
- } else if (*in < 224) {
- *out = ((uint32_t(in[0]) << 16) |
- (uint32_t(in[2]) << 8) |
- (uint32_t(in[1]))) & 0x1fffff;
- return in + 3;
- } else {
- assert(false); // Not implemented.
- }
-}
-
-template<class Docid>
-const unsigned char *read_vb(const unsigned char *in, Docid *out)
-{
- if (*in <= 176) {
- *out = *in;
- return in + 1;
- } else if (*in <= 240) {
- *out = ((uint32_t(in[0] - 177) << 8) | uint32_t(in[1])) + 177;
- return in + 2;
- } else if (*in <= 248) {
- *out = ((uint32_t(in[0] - 241) << 16) | read_le<uint16_t>(in + 1)) + 16561;
- return in + 3;
- } else if (*in == 249) {
- *out = (uint32_t(in[1])) |
- (uint32_t(in[2]) << 8) |
- (uint32_t(in[3]) << 16);
- return in + 4;
- } else if (*in == 250) {
- *out = read_le<uint32_t>(in + 1);
- return in + 5;
- } else {
- assert(false);
- }
-}
-
-struct BitReader {
-public:
- BitReader(const unsigned char *in, unsigned bits)
- : in(in), bits(bits), mask(mask_for_bits(bits)) {}
- uint32_t read()
- {
- uint32_t val = (read_le<uint32_t>(in) >> bits_used) & mask;
-
- bits_used += bits;
- in += bits_used / 8;
- bits_used %= 8;
-
- return val;
- }
-
-private:
- const unsigned char *in;
- const unsigned bits;
- const unsigned mask;
- unsigned bits_used = 0;
-};
-
-template<unsigned NumStreams>
-struct InterleavedBitReader {
-public:
- InterleavedBitReader(const unsigned char *in, unsigned bits)
- : in(in), bits(bits), mask(mask_for_bits(bits)) {}
- uint32_t read()
- {
- uint32_t val;
- if (bits_used + bits > 32) {
- val = (read_le<uint32_t>(in) >> bits_used) | (read_le<uint32_t>(in + Stride) << (32 - bits_used));
- } else {
- val = (read_le<uint32_t>(in) >> bits_used);
- }
-
- bits_used += bits;
- in += Stride * (bits_used / 32);
- bits_used %= 32;
-
- return val & mask;
- }
-
-private:
- static constexpr unsigned Stride = NumStreams * sizeof(uint32_t);
- const unsigned char *in;
- const unsigned bits;
- const unsigned mask;
- unsigned bits_used = 0;
-};
-
-#ifdef COULD_HAVE_SSE2
-struct InterleavedBitReaderSSE2 {
-public:
- InterleavedBitReaderSSE2(const unsigned char *in, unsigned bits)
- : in(reinterpret_cast<const __m128i *>(in)), bits(bits), mask(_mm_set1_epi32(mask_for_bits(bits))) {}
- __m128i read() {
- __m128i val = _mm_srli_epi32(_mm_loadu_si128(in), bits_used);
- if (bits_used + bits > 32) {
- __m128i val_upper = _mm_slli_epi32(_mm_loadu_si128(in + 1), 32 - bits_used);
- val = _mm_or_si128(val, val_upper);
- }
- val = _mm_and_si128(val, mask);
-
- bits_used += bits;
- in += bits_used / 32;
- bits_used %= 32;
- return val;
- }
-
-private:
- const __m128i *in;
- const unsigned bits;
- const __m128i mask;
- unsigned bits_used = 0;
-};
-#endif
-
-// Does not properly account for overflow.
-inline unsigned div_round_up(unsigned val, unsigned div)
-{
- return (val + div - 1) / div;
-}
-
-inline unsigned bytes_for_packed_bits(unsigned num, unsigned bit_width)
-{
- return div_round_up(num * bit_width, CHAR_BIT);
-}
-
-// Constant block. Layout:
//
-// - Bit width (6 bits) | type << 6
-// - Base values (<bits> bits, rounded up to nearest byte)
-template<class Docid>
-const unsigned char *decode_constant(const unsigned char *in, unsigned num, Docid *out)
-{
- const unsigned bit_width = *in++ & 0x3f;
- Docid val = read_le<Docid>(in);
- if (bit_width < sizeof(Docid) * 8) {
- val &= mask_for_bits(bit_width);
- }
-
- Docid prev_val = out[-1];
- for (unsigned i = 0; i < num; ++i) {
- out[i] = prev_val = val + prev_val + 1;
- }
- return in + div_round_up(bit_width, 8);
-}
-
-// FOR block (ie., PFor without exceptions). Layout:
+// The decoder, like the reference implementation, is not robust against
+// malicious of corrupted. Several functions (again like the reference
+// implementation) can read N bytes past the end, so you need to have some slop
+// in the input buffers; this is documented for each function (unlike
+// the reference implementation), but the documented slop assumes a
+// non-malicious encoder.
//
-// - Bit width (6 bits) | type << 6
-// - Base values (<num> values of <bits> bits, rounded up to a multiple of 32 values)
-template<class Docid>
-const unsigned char *decode_for(const unsigned char *in, unsigned num, Docid *out)
-{
- const unsigned bit_width = *in++ & 0x3f;
-
- Docid prev_val = out[-1];
- BitReader bs(in, bit_width);
- for (unsigned i = 0; i < num; ++i) {
- prev_val = out[i] = bs.read() + prev_val + 1;
- }
- return in + bytes_for_packed_bits(num, bit_width);
-}
-
-#ifdef COULD_HAVE_SSE2
-class DeltaDecoderSSE2 {
-public:
- DeltaDecoderSSE2(uint32_t prev_val) : prev_val(_mm_set1_epi32(prev_val)) {}
- __m128i decode(__m128i val) {
- val = _mm_add_epi32(val, _mm_slli_si128(val, 4));
- val = _mm_add_epi32(val, _mm_slli_si128(val, 8));
- val = _mm_add_epi32(val, _mm_add_epi32(prev_val, delta));
- prev_val = _mm_shuffle_epi32(val, _MM_SHUFFLE(3, 3, 3, 3));
- return val;
- }
-
-private:
- // Use 4/3/2/1 as delta instead of fixed 1, so that we can do the prev_val + delta
- // in parallel with something else.
- const __m128i delta = _mm_set_epi32(4, 3, 2, 1);
-
- __m128i prev_val;
-};
-
-template<unsigned BlockSize>
-__attribute__((target("sse2")))
-inline void delta_decode_sse2(uint32_t *out)
-{
- DeltaDecoderSSE2 delta(out[-1]);
- __m128i *outvec = reinterpret_cast<__m128i *>(out);
- for (unsigned i = 0; i < BlockSize / 4; ++i) {
- __m128i val = _mm_loadu_si128(outvec + i);
- _mm_storeu_si128(outvec + i, delta.decode(val));
- }
-}
-
-template<unsigned BlockSize, bool OrWithExisting, bool DeltaDecode, unsigned bit_width>
-__attribute__((target("sse2")))
-const unsigned char *decode_bitmap_sse2_unrolled(const unsigned char *in, uint32_t *out)
-{
- __m128i *outvec = reinterpret_cast<__m128i *>(out);
- DeltaDecoderSSE2 delta(out[-1]);
- InterleavedBitReaderSSE2 bs(in, bit_width);
- #pragma GCC unroll 32
- for (unsigned i = 0; i < BlockSize / 4; ++i) {
- __m128i val = bs.read();
- if constexpr (OrWithExisting) {
- val = _mm_or_si128(val, _mm_slli_epi32(_mm_loadu_si128(outvec + i), bit_width));
- }
- if constexpr (DeltaDecode) {
- val = delta.decode(val);
- }
- _mm_storeu_si128(outvec + i, val);
- }
- in += bytes_for_packed_bits(BlockSize, bit_width);
- return in;
-}
-
-template<unsigned BlockSize, bool OrWithExisting, bool DeltaDecode>
-__attribute__((target("sse2")))
-const unsigned char *decode_bitmap_sse2(const unsigned char *in, unsigned bit_width, uint32_t *out)
-{
- switch (bit_width) {
- case 0: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 0>(in, out);
- case 1: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 1>(in, out);
- case 2: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 2>(in, out);
- case 3: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 3>(in, out);
- case 4: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 4>(in, out);
- case 5: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 5>(in, out);
- case 6: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 6>(in, out);
- case 7: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 7>(in, out);
- case 8: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 8>(in, out);
- case 9: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 9>(in, out);
- case 10: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 10>(in, out);
- case 11: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 11>(in, out);
- case 12: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 12>(in, out);
- case 13: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 13>(in, out);
- case 14: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 14>(in, out);
- case 15: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 15>(in, out);
- case 16: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 16>(in, out);
- case 17: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 17>(in, out);
- case 18: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 18>(in, out);
- case 19: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 19>(in, out);
- case 20: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 20>(in, out);
- case 21: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 21>(in, out);
- case 22: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 22>(in, out);
- case 23: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 23>(in, out);
- case 24: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 24>(in, out);
- case 25: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 25>(in, out);
- case 26: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 26>(in, out);
- case 27: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 27>(in, out);
- case 28: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 28>(in, out);
- case 29: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 29>(in, out);
- case 30: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 30>(in, out);
- case 31: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 31>(in, out);
- case 32: return decode_bitmap_sse2_unrolled<BlockSize, OrWithExisting, DeltaDecode, 32>(in, out);
- }
- assert(false);
-}
-#endif
-
-// Like decode_for(), but the values are organized in four independent streams,
-// for SIMD (presumably SSE2). Supports a whole block only.
-template<unsigned BlockSize, class Docid>
-const unsigned char *decode_for_interleaved_generic(const unsigned char *in, Docid *out)
-{
- const unsigned bit_width = *in++ & 0x3f;
-
- InterleavedBitReader<4> bs0(in + 0 * sizeof(uint32_t), bit_width);
- InterleavedBitReader<4> bs1(in + 1 * sizeof(uint32_t), bit_width);
- InterleavedBitReader<4> bs2(in + 2 * sizeof(uint32_t), bit_width);
- InterleavedBitReader<4> bs3(in + 3 * sizeof(uint32_t), bit_width);
- for (unsigned i = 0; i < BlockSize / 4; ++i) {
- out[i * 4 + 0] = bs0.read();
- out[i * 4 + 1] = bs1.read();
- out[i * 4 + 2] = bs2.read();
- out[i * 4 + 3] = bs3.read();
- }
- Docid prev_val = out[-1];
- for (unsigned i = 0; i < BlockSize; ++i) {
- out[i] = prev_val = out[i] + prev_val + 1;
- }
- return in + bytes_for_packed_bits(BlockSize, bit_width);
-}
-
-template<unsigned BlockSize, class Docid>
-const unsigned char *decode_for_interleaved(const unsigned char *in, Docid *out)
-{
- if constexpr (BlockSize == 128 && sizeof(Docid) == sizeof(uint32_t)) {
- return decode_for_interleaved_128_32(in, out);
- } else {
- return decode_for_interleaved_generic(in, out);
- }
-}
-
-__attribute__((target("default")))
-const unsigned char *decode_for_interleaved_128_32(const unsigned char *in, uint32_t *out)
-{
- return decode_for_interleaved_generic<128>(in, out);
-}
-
-#ifdef COULD_HAVE_SSE2
-// Specialized version for SSE2.
-__attribute__((target("sse2")))
-const unsigned char *decode_for_interleaved_128_32(const unsigned char *in, uint32_t *out)
-{
- constexpr unsigned BlockSize = 128;
-
- const unsigned bit_width = *in++ & 0x3f;
-
- in = decode_bitmap_sse2<BlockSize, /*OrWithExisting=*/false, /*DeltaDecode=*/true>(in, bit_width, out);
-
- return in;
-}
-#endif
-
-template<class Docid>
-const unsigned char *decode_pfor_bitmap_exceptions(const unsigned char *in, unsigned num, Docid *out)
-{
- const unsigned exception_bit_width = *in++;
- const uint64_t *exception_bitmap_ptr = reinterpret_cast<const uint64_t *>(in);
- in += div_round_up(num, 8);
-
- int num_exceptions = 0;
-
- BitReader bs(in, exception_bit_width);
- for (unsigned i = 0; i < num; i += 64, ++exception_bitmap_ptr) {
- uint64_t exceptions = read_le<uint64_t>(exception_bitmap_ptr);
- if (num - i < 64) {
- // We've read some bytes past the end, so clear out the junk bits.
- exceptions &= (1ULL << (num - i)) - 1;
- }
- for (; exceptions != 0; exceptions &= exceptions - 1, ++num_exceptions) {
- unsigned idx = (ffsll(exceptions) - 1) + i;
- out[idx] = bs.read();
- }
- }
- in += bytes_for_packed_bits(num_exceptions, exception_bit_width);
- return in;
-}
-
-// PFor block with bitmap exceptions. Layout:
-//
-// - Bit width (6 bits) | type << 6
-// - Exception bit width (8 bits)
-// - Bitmap of which values have exceptions (<num> bits, rounded up to a byte)
-// - Exceptions (<num_exc> values of <bits_exc> bits, rounded up to a byte)
-// - Base values (<num> values of <bits> bits, rounded up to a byte)
-template<class Docid>
-const unsigned char *decode_pfor_bitmap(const unsigned char *in, unsigned num, Docid *out)
-{
- memset(out, 0, num * sizeof(Docid));
-
- const unsigned bit_width = *in++ & 0x3f;
-
- in = decode_pfor_bitmap_exceptions(in, num, out);
-
- // Decode the base values, and delta-decode.
- Docid prev_val = out[-1];
- BitReader bs(in, bit_width);
- for (unsigned i = 0; i < num; ++i) {
- out[i] = prev_val = ((out[i] << bit_width) | bs.read()) + prev_val + 1;
- }
- return in + bytes_for_packed_bits(num, bit_width);
-}
-
-// Like decode_pfor_bitmap(), but the base values are organized in four
-// independent streams, for SIMD (presumably SSE2). Supports a whole block only.
-template<unsigned BlockSize, class Docid>
-const unsigned char *decode_pfor_bitmap_interleaved_generic(const unsigned char *in, Docid *out)
-{
- memset(out, 0, BlockSize * sizeof(Docid));
-
- const unsigned bit_width = *in++ & 0x3f;
-
- in = decode_pfor_bitmap_exceptions(in, BlockSize, out);
-
- // Decode the base values.
- InterleavedBitReader<4> bs0(in + 0 * sizeof(uint32_t), bit_width);
- InterleavedBitReader<4> bs1(in + 1 * sizeof(uint32_t), bit_width);
- InterleavedBitReader<4> bs2(in + 2 * sizeof(uint32_t), bit_width);
- InterleavedBitReader<4> bs3(in + 3 * sizeof(uint32_t), bit_width);
- for (unsigned i = 0; i < BlockSize / 4; ++i) {
- out[i * 4 + 0] = bs0.read() | (out[i * 4 + 0] << bit_width);
- out[i * 4 + 1] = bs1.read() | (out[i * 4 + 1] << bit_width);
- out[i * 4 + 2] = bs2.read() | (out[i * 4 + 2] << bit_width);
- out[i * 4 + 3] = bs3.read() | (out[i * 4 + 3] << bit_width);
- }
-
- // Delta-decode.
- Docid prev_val = out[-1];
- for (unsigned i = 0; i < BlockSize; ++i) {
- out[i] = prev_val = out[i] + prev_val + 1;
- }
- return in + bytes_for_packed_bits(BlockSize, bit_width);
-}
-
-template<unsigned BlockSize, class Docid>
-const unsigned char *decode_pfor_bitmap_interleaved(const unsigned char *in, Docid *out)
-{
- if constexpr (BlockSize == 128 && sizeof(Docid) == sizeof(uint32_t)) {
- return decode_pfor_bitmap_interleaved_128_32(in, out);
- } else {
- return decode_pfor_bitmap_interleaved_generic(in, out);
- }
-}
-
-__attribute__((target("default")))
-const unsigned char *decode_pfor_bitmap_interleaved_128_32(const unsigned char *in, uint32_t *out)
-{
- return decode_pfor_bitmap_interleaved_generic<128>(in, out);
-}
-
-#ifdef COULD_HAVE_SSE2
-// Specialized version for SSE2.
-__attribute__((target("sse2")))
-const unsigned char *decode_pfor_bitmap_interleaved_128_32(const unsigned char *in, uint32_t *out)
-{
- constexpr unsigned BlockSize = 128;
- using Docid = uint32_t;
-
- memset(out, 0, BlockSize * sizeof(Docid));
-
- const unsigned bit_width = *in++ & 0x3f;
-
- in = decode_pfor_bitmap_exceptions(in, BlockSize, out);
- in = decode_bitmap_sse2<BlockSize, /*OrWithExisting=*/true, /*DeltaDecode=*/true>(in, bit_width, out);
-
- return in;
-}
-#endif
-
-// PFor block with variable-byte exceptions. Layout:
-//
-// - Bit width (6 bits) | type << 6
-// - Number of exceptions (8 bits)
-// - Base values (<num> values of <bits> bits, rounded up to a byte)
-// - Exceptions:
-// - If first byte is 255, <num_exc> 32-bit values (does not include the 255 byte)
-// - Else, <num_exc> varbyte-encoded values (includes the non-255 byte)
-// - Indexes of exceptions (<num_exc> bytes).
-template<unsigned BlockSize, class Docid>
-const unsigned char *decode_pfor_vb(const unsigned char *in, unsigned num, Docid *out)
-{
- //fprintf(stderr, "in=%p out=%p num=%u\n", in, out, num);
-
- const unsigned bit_width = *in++ & 0x3f;
- unsigned num_exceptions = *in++;
-
- // Decode the base values.
- BitReader bs(in, bit_width);
- for (unsigned i = 0; i < num; ++i) {
- out[i] = bs.read();
- }
- in += bytes_for_packed_bits(num, bit_width);
-
- // Decode exceptions.
- Docid exceptions[BlockSize];
- if (*in == 255) {
- ++in;
- for (unsigned i = 0; i < num_exceptions; ++i) {
- exceptions[i] = read_le<Docid>(in);
- in += sizeof(Docid);
- }
- } else {
- for (unsigned i = 0; i < num_exceptions; ++i) {
- in = read_vb(in, &exceptions[i]);
- }
- }
- // Apply exceptions.
- for (unsigned i = 0; i < num_exceptions; ++i) {
- unsigned idx = *in++;
- out[idx] |= exceptions[i] << bit_width;
- }
-
- // Delta-decode.
- Docid prev_val = out[-1];
- for (unsigned i = 0; i < num; ++i) {
- out[i] = prev_val = out[i] + prev_val + 1;
- }
-
- return in;
-}
-
-// Like decode_pfor_vb(), but the base values are organized in four
-// independent streams, for SIMD (presumably SSE2). Supports a whole block only.
-template<unsigned BlockSize, class Docid>
-const unsigned char *decode_pfor_vb_interleaved_generic(const unsigned char *in, Docid *out)
-{
- const unsigned bit_width = *in++ & 0x3f;
- unsigned num_exceptions = *in++;
-
- // Decode the base values.
- InterleavedBitReader<4> bs0(in + 0 * sizeof(uint32_t), bit_width);
- InterleavedBitReader<4> bs1(in + 1 * sizeof(uint32_t), bit_width);
- InterleavedBitReader<4> bs2(in + 2 * sizeof(uint32_t), bit_width);
- InterleavedBitReader<4> bs3(in + 3 * sizeof(uint32_t), bit_width);
- for (unsigned i = 0; i < BlockSize / 4; ++i) {
- out[i * 4 + 0] = bs0.read();
- out[i * 4 + 1] = bs1.read();
- out[i * 4 + 2] = bs2.read();
- out[i * 4 + 3] = bs3.read();
- }
- in += bytes_for_packed_bits(BlockSize, bit_width);
-
- // Decode exceptions.
- Docid exceptions[BlockSize];
- if (*in == 255) {
- ++in;
- for (unsigned i = 0; i < num_exceptions; ++i) {
- exceptions[i] = read_le<Docid>(in);
- in += sizeof(Docid);
- }
- } else {
- for (unsigned i = 0; i < num_exceptions; ++i) {
- in = read_vb(in, &exceptions[i]);
- }
- }
-
- // Apply exceptions.
- for (unsigned i = 0; i < num_exceptions; ++i) {
- unsigned idx = *in++;
- out[idx] |= exceptions[i] << bit_width;
- }
-
- // Delta-decode.
- Docid prev_val = out[-1];
- for (unsigned i = 0; i < BlockSize; ++i) {
- out[i] = prev_val = out[i] + prev_val + 1;
- }
-
- return in;
-}
-
-template<unsigned BlockSize, class Docid>
-const unsigned char *decode_pfor_vb_interleaved(const unsigned char *in, Docid *out)
-{
- if constexpr (BlockSize == 128 && sizeof(Docid) == sizeof(uint32_t)) {
- return decode_pfor_vb_interleaved_128_32(in, out);
- } else {
- return decode_pfor_vb_interleaved_generic(in, out);
- }
-}
-
-__attribute__((target("default")))
-const unsigned char *decode_pfor_vb_interleaved_128_32(const unsigned char *in, uint32_t *out)
-{
- return decode_pfor_vb_interleaved_generic<128>(in, out);
-}
-
-// Specialized version for SSE2.
-__attribute__((target("sse2")))
-const unsigned char *decode_pfor_vb_interleaved_128_32(const unsigned char *in, uint32_t *out)
-{
- constexpr unsigned BlockSize = 128;
- using Docid = uint32_t;
-
- const unsigned bit_width = *in++ & 0x3f;
- unsigned num_exceptions = *in++;
-
- // Decode the base values.
- in = decode_bitmap_sse2<BlockSize, /*OrWithExisting=*/false, /*DeltaDecode=*/false>(in, bit_width, out);
-
- // Decode exceptions.
- Docid exceptions[BlockSize];
- if (*in == 255) {
- ++in;
- for (unsigned i = 0; i < num_exceptions; ++i) {
- exceptions[i] = read_le<Docid>(in);
- in += sizeof(Docid);
- }
- } else {
- for (unsigned i = 0; i < num_exceptions; ++i) {
- in = read_vb(in, &exceptions[i]);
- }
- }
-
- // Apply exceptions.
- for (unsigned i = 0; i < num_exceptions; ++i) {
- unsigned idx = *in++;
- out[idx] |= exceptions[i] << bit_width;
- }
-
- delta_decode_sse2<BlockSize>(out);
-
- return in;
-}
-
-enum BlockType {
- FOR = 0,
- PFOR_VB = 1,
- PFOR_BITMAP = 2,
- CONSTANT = 3
-};
-
-template<unsigned BlockSize, class Docid>
-const unsigned char *decode_pfor_delta1(const unsigned char *in, unsigned num, bool interleaved, Docid *out)
-{
- if (num == 0) {
- return in;
- }
- in = read_baseval(in, out++);
-
- for (unsigned i = 1; i < num; i += BlockSize, out += BlockSize) {
- const unsigned num_this_block = std::min<unsigned>(num - i, BlockSize);
- switch (in[0] >> 6) {
- case BlockType::FOR:
- if (interleaved && num_this_block == BlockSize) {
- dprintf("%d+%d: blocktype=%d (for, interleaved), bitwidth=%d\n", i, num_this_block, in[0] >> 6, in[0] & 0x3f);
- in = decode_for_interleaved<BlockSize>(in, out);
- } else {
- dprintf("%d+%d: blocktype=%d (for), bitwidth=%d\n", i, num_this_block, in[0] >> 6, in[0] & 0x3f);
- in = decode_for(in, num_this_block, out);
- }
- break;
- case BlockType::PFOR_VB:
- if (interleaved && num_this_block == BlockSize) {
- dprintf("%d+%d: blocktype=%d (pfor + vb, interleaved), bitwidth=%d\n", i, num_this_block, in[0] >> 6, in[0] & 0x3f);
- in = decode_pfor_vb_interleaved<BlockSize>(in, out);
- } else {
- dprintf("%d+%d: blocktype=%d (pfor + vb), bitwidth=%d\n", i, num_this_block, in[0] >> 6, in[0] & 0x3f);
- in = decode_pfor_vb<BlockSize>(in, num_this_block, out);
- }
- break;
- case BlockType::PFOR_BITMAP:
- if (interleaved && num_this_block == BlockSize) {
- dprintf("%d+%d: blocktype=%d (pfor + bitmap, interleaved), bitwidth=%d\n", i, num_this_block, in[0] >> 6, in[0] & 0x3f);
- in = decode_pfor_bitmap_interleaved<BlockSize>(in, out);
- } else {
- dprintf("%d+%d: blocktype=%d (pfor + bitmap), bitwidth=%d\n", i, num_this_block, in[0] >> 6, in[0] & 0x3f);
- in = decode_pfor_bitmap(in, num_this_block, out);
- }
- break;
- case BlockType::CONSTANT:
- dprintf("%d+%d: blocktype=%d (constant), bitwidth=%d\n", i, num_this_block, in[0] >> 6, in[0] & 0x3f);
- in = decode_constant(in, num_this_block, out);
- break;
- }
- }
+// Although all of these algorithms are templatized, we expose only
+// the single specialization that we need, in order to increase the
+// speed of incremental compilation.
- return in;
-}
+const unsigned char *decode_pfor_delta1_128(const unsigned char *in, unsigned num, bool interleaved, uint32_t *out);
#endif // !defined(_TURBOPFOR_H)
projects / plocate / blobdiff