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| 1 | +static inline int |
| 2 | +is_nonzero (const uint8x16_t v) |
| 3 | +{ |
| 4 | + uint64_t u64; |
| 5 | + const uint64x2_t v64 = vreinterpretq_u64_u8(v); |
| 6 | + const uint32x2_t v32 = vqmovn_u64(v64); |
| 7 | + |
| 8 | + vst1_u64(&u64, vreinterpret_u64_u32(v32)); |
| 9 | + return u64 != 0; |
| 10 | +} |
| 11 | + |
| 12 | +static inline uint8x16_t |
| 13 | +delta_lookup (const uint8x16_t v) |
| 14 | +{ |
| 15 | + const uint8x8_t lut = { |
| 16 | + 0, 16, 19, 4, (uint8_t) -65, (uint8_t) -65, (uint8_t) -71, (uint8_t) -71, |
| 17 | + }; |
| 18 | + |
| 19 | + return vcombine_u8( |
| 20 | + vtbl1_u8(lut, vget_low_u8(v)), |
| 21 | + vtbl1_u8(lut, vget_high_u8(v))); |
| 22 | +} |
| 23 | + |
| 24 | +static inline uint8x16_t |
| 25 | +dec_loop_neon32_lane (uint8x16_t *lane) |
| 26 | +{ |
| 27 | + // See the SSSE3 decoder for an explanation of the algorithm. |
| 28 | + const uint8x16_t lut_lo = { |
| 29 | + 0x15, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11, |
| 30 | + 0x11, 0x11, 0x13, 0x1A, 0x1B, 0x1B, 0x1B, 0x1A |
| 31 | + }; |
| 32 | + |
| 33 | + const uint8x16_t lut_hi = { |
| 34 | + 0x10, 0x10, 0x01, 0x02, 0x04, 0x08, 0x04, 0x08, |
| 35 | + 0x10, 0x10, 0x10, 0x10, 0x10, 0x10, 0x10, 0x10 |
| 36 | + }; |
| 37 | + |
| 38 | + const uint8x16_t mask_0F = vdupq_n_u8(0x0F); |
| 39 | + const uint8x16_t mask_2F = vdupq_n_u8(0x2F); |
| 40 | + |
| 41 | + const uint8x16_t hi_nibbles = vshrq_n_u8(*lane, 4); |
| 42 | + const uint8x16_t lo_nibbles = vandq_u8(*lane, mask_0F); |
| 43 | + const uint8x16_t eq_2F = vceqq_u8(*lane, mask_2F); |
| 44 | + |
| 45 | + const uint8x16_t hi = vqtbl1q_u8(lut_hi, hi_nibbles); |
| 46 | + const uint8x16_t lo = vqtbl1q_u8(lut_lo, lo_nibbles); |
| 47 | + |
| 48 | + // Now simply add the delta values to the input: |
| 49 | + *lane = vaddq_u8(*lane, delta_lookup(vaddq_u8(eq_2F, hi_nibbles))); |
| 50 | + |
| 51 | + // Return the validity mask: |
| 52 | + return vandq_u8(lo, hi); |
| 53 | +} |
| 54 | + |
| 55 | +static inline void |
| 56 | +dec_loop_neon32 (const uint8_t **s, size_t *slen, uint8_t **o, size_t *olen) |
| 57 | +{ |
| 58 | + if (*slen < 64) { |
| 59 | + return; |
| 60 | + } |
| 61 | + |
| 62 | + // Process blocks of 64 bytes per round. Unlike the SSE codecs, no |
| 63 | + // extra trailing zero bytes are written, so it is not necessary to |
| 64 | + // reserve extra input bytes: |
| 65 | + size_t rounds = *slen / 64; |
| 66 | + |
| 67 | + *slen -= rounds * 64; // 64 bytes consumed per round |
| 68 | + *olen += rounds * 48; // 48 bytes produced per round |
| 69 | + |
| 70 | + do { |
| 71 | + uint8x16x3_t dec; |
| 72 | + |
| 73 | + // Load 64 bytes and deinterleave: |
| 74 | + uint8x16x4_t str = vld4q_u8(*s); |
| 75 | + |
| 76 | + // Decode each lane, collect a mask of invalid inputs: |
| 77 | + const uint8x16_t classified |
| 78 | + = dec_loop_neon32_lane(&str.val[0]) |
| 79 | + | dec_loop_neon32_lane(&str.val[1]) |
| 80 | + | dec_loop_neon32_lane(&str.val[2]) |
| 81 | + | dec_loop_neon32_lane(&str.val[3]); |
| 82 | + |
| 83 | + // Check for invalid input: if any of the delta values are |
| 84 | + // zero, fall back on bytewise code to do error checking and |
| 85 | + // reporting: |
| 86 | + if (is_nonzero(classified)) { |
| 87 | + break; |
| 88 | + } |
| 89 | + |
| 90 | + // Compress four bytes into three: |
| 91 | + dec.val[0] = vorrq_u8(vshlq_n_u8(str.val[0], 2), vshrq_n_u8(str.val[1], 4)); |
| 92 | + dec.val[1] = vorrq_u8(vshlq_n_u8(str.val[1], 4), vshrq_n_u8(str.val[2], 2)); |
| 93 | + dec.val[2] = vorrq_u8(vshlq_n_u8(str.val[2], 6), str.val[3]); |
| 94 | + |
| 95 | + // Interleave and store decoded result: |
| 96 | + vst3q_u8(*o, dec); |
| 97 | + |
| 98 | + *s += 64; |
| 99 | + *o += 48; |
| 100 | + |
| 101 | + } while (--rounds > 0); |
| 102 | + |
| 103 | + // Adjust for any rounds that were skipped: |
| 104 | + *slen += rounds * 64; |
| 105 | + *olen -= rounds * 48; |
| 106 | +} |
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