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Diffstat (limited to '')
-rw-r--r-- | src/third-party/base64/lib/arch/avx2/enc_translate.c | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/src/third-party/base64/lib/arch/avx2/enc_translate.c b/src/third-party/base64/lib/arch/avx2/enc_translate.c new file mode 100644 index 0000000..46173cd --- /dev/null +++ b/src/third-party/base64/lib/arch/avx2/enc_translate.c @@ -0,0 +1,30 @@ +static inline __m256i +enc_translate (const __m256i in) +{ + // A lookup table containing the absolute offsets for all ranges: + const __m256i lut = _mm256_setr_epi8( + 65, 71, -4, -4, -4, -4, -4, -4, -4, -4, -4, -4, -19, -16, 0, 0, + 65, 71, -4, -4, -4, -4, -4, -4, -4, -4, -4, -4, -19, -16, 0, 0); + + // Translate values 0..63 to the Base64 alphabet. There are five sets: + // # From To Abs Index Characters + // 0 [0..25] [65..90] +65 0 ABCDEFGHIJKLMNOPQRSTUVWXYZ + // 1 [26..51] [97..122] +71 1 abcdefghijklmnopqrstuvwxyz + // 2 [52..61] [48..57] -4 [2..11] 0123456789 + // 3 [62] [43] -19 12 + + // 4 [63] [47] -16 13 / + + // Create LUT indices from the input. The index for range #0 is right, + // others are 1 less than expected: + __m256i indices = _mm256_subs_epu8(in, _mm256_set1_epi8(51)); + + // mask is 0xFF (-1) for range #[1..4] and 0x00 for range #0: + const __m256i mask = _mm256_cmpgt_epi8(in, _mm256_set1_epi8(25)); + + // Subtract -1, so add 1 to indices for range #[1..4]. All indices are + // now correct: + indices = _mm256_sub_epi8(indices, mask); + + // Add offsets to input values: + return _mm256_add_epi8(in, _mm256_shuffle_epi8(lut, indices)); +} |