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https://github.com/matrix-construct/construct
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ircd::utf: Complete the branchless UTF-8 decoder.
This commit is contained in:
Jason Volk
parent
1eec9bfd64
commit
f1e76604d0
1 changed files with 70 additions and 50 deletions
120
ircd/utf.cc
120
ircd/utf.cc
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@ -302,82 +302,102 @@ noexcept
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//
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ircd::u32x16
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ircd::utf8::decode(const u8x16 string)
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ircd::utf8::decode(const u8x16 in)
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noexcept
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{
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const u32x16 in
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(
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simd::lane_cast<u32x16, u8x16>(string)
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);
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const u32x16 is_single
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const u8x16 is_single
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(
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(in & 0x80) == 0
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);
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const u32x16 is_lead
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const u8x16 is_lead
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(
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(in - 0xc2) <= 0x32
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);
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const u32x16 is_trail
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const u8x16 is_trail
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(
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in >= 0x80 && in < 0xbf
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);
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const u32x16 expect_trail
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const u8x16 is_head
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(
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is_lead | is_single
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);
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const u8x16 len_mask[3]
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{
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(((in >= 0xe0) & 1) + ((in >= 0xf0) & 1) + 1) & is_lead
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in >= 0xc0, in >= 0xe0, in >= 0xf0,
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};
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const u32x16 expect_length
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const u8x16 expect_trail
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(
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1 + (len_mask[0] & 1) + (len_mask[1] & 1) + (len_mask[2] & 1)
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);
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const u8x16 len
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(
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(is_single & 1) | (is_lead & expect_trail)
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);
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const u8x16 head
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(
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in & is_head
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);
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const u8x16 lead[]
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{
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expect_trail + 1
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0x3f & in & is_trail,
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0xff & head & is_single,
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0x1f & head & len_mask[0] & ~len_mask[1],
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0x0f & head & len_mask[1] & ~len_mask[2],
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0x07 & head & len_mask[2],
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};
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const u32x16 shift[4]
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u8x16 full;
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for(uint i(0); i < 16; ++i)
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full[i] = lead[len[i]][i];
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u8x16 shift {len & is_head};
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shift |= (shl<0x20>(len) == 4) & 0;
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shift |= (shl<0x20>(len) == 3) & 0;
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shift |= (shl<0x20>(len) == 2) & 0;
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shift |= (shl<0x20>(len) == 1) & 0;
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shift |= (shl<0x18>(len) == 4) & 1;
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shift |= (shl<0x18>(len) == 3) & 0;
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shift |= (shl<0x18>(len) == 2) & 0;
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shift |= (shl<0x18>(len) == 1) & 0;
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shift |= (shl<0x10>(len) == 4) & 2;
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shift |= (shl<0x10>(len) == 3) & 1;
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shift |= (shl<0x10>(len) == 2) & 0;
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shift |= (shl<0x10>(len) == 1) & 0;
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shift |= (shl<0x08>(len) == 4) & 3;
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shift |= (shl<0x08>(len) == 3) & 2;
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shift |= (shl<0x08>(len) == 2) & 1;
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shift |= (shl<0x08>(len) == 1) & 0;
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shift -= 1U;
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shift &= 0x03U;
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shift *= 6U;
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const u32x16 val
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{
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in << 0,
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in << 8,
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in << 16,
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in << 24,
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lane_cast<u32x16>(full) << lane_cast<u32x16>(shift)
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};
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const u32x16 multibyte_packs
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{
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in[0x00] | shift[0x01][0x01] | shift[0x02][0x02] | shift[0x03][0x03],
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in[0x01] | shift[0x01][0x02] | shift[0x02][0x03] | shift[0x03][0x04],
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in[0x02] | shift[0x01][0x03] | shift[0x02][0x04] | shift[0x03][0x05],
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in[0x03] | shift[0x01][0x04] | shift[0x02][0x05] | shift[0x03][0x06],
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in[0x04] | shift[0x01][0x05] | shift[0x02][0x06] | shift[0x03][0x07],
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in[0x05] | shift[0x01][0x06] | shift[0x02][0x07] | shift[0x03][0x08],
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in[0x06] | shift[0x01][0x07] | shift[0x02][0x08] | shift[0x03][0x09],
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in[0x07] | shift[0x01][0x08] | shift[0x02][0x09] | shift[0x03][0x0a],
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in[0x08] | shift[0x01][0x09] | shift[0x02][0x0a] | shift[0x03][0x0b],
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in[0x09] | shift[0x01][0x0a] | shift[0x02][0x0b] | shift[0x03][0x0c],
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in[0x0a] | shift[0x01][0x0b] | shift[0x02][0x0c] | shift[0x03][0x0d],
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in[0x0b] | shift[0x01][0x0c] | shift[0x02][0x0d] | shift[0x03][0x0e],
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in[0x0c] | shift[0x01][0x0d] | shift[0x02][0x0e] | shift[0x03][0x0f],
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in[0x0d] | shift[0x01][0x0e] | shift[0x02][0x0f] | shift[0x03][0x0f],
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in[0x0e] | shift[0x01][0x0f] | shift[0x02][0x0f] | shift[0x03][0x0f],
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in[0x0f] | shift[0x01][0x0f] | shift[0x02][0x0f] | shift[0x03][0x0f],
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};
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const u8x16 incr
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(
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(shift == 0) & 1U
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);
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const u32x16 multibyte
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{
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0
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| (multibyte_packs & (expect_length == 1) & 0x000000ffU)
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| (multibyte_packs & (expect_length == 2) & 0x0000ffffU)
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| (multibyte_packs & (expect_length == 3) & 0x00ffffffU)
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| (multibyte_packs & (expect_length == 4) & 0xffffffffU)
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};
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u8x16 idx {0};
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for(uint i(1); i < 16; ++i)
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idx[i] = idx[i - 1] + incr[i - 1];
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const u32x16 integers
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{
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(in & is_single) | (multibyte & is_lead)
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};
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u32x16 ret {0};
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for(uint i(0); i < 16; ++i)
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ret[idx[i]] |= val[i];
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return integers;
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return ret;
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}
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namespace ircd::utf8
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