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ircd::json: Reduce string serialized/stringify branch complex and improve layout.

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This commit is contained in:
Jason Volk 2020-07-15 17:26:59 -07:00
parent 0e37275773
commit ba5a97821c
1 changed files with 121 additions and 101 deletions
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138
ircd/json.cc
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@ -3416,17 +3416,20 @@ ircd::json::string_stringify(u8x16 &__restrict__ block,
regular_prefix_count, regular_prefix_count,
};
// Slow-path; decide what to do based on the next character.
switch(block[0])
// Unescaped quote case
if(is_quote[0])
{
// Covers the ctrl 0x00-0x20 range only; no other character here.
default:
block[0] = '\\';
block[1] = '"';
return u64x2
{
assert(block[0] < 0x20);
#if __has_builtin(__builtin_assume)
__builtin_assume(block[0] < 0x20);
#endif
1, 2
};
}
// Control character case
if(is_ctrl[0])
{
const u8 idx{block[0]};
block = *reinterpret_cast<const u128x1 *>(ctrl_tab + idx);
return u64x2
@ -3435,46 +3438,56 @@ ircd::json::string_stringify(u8x16 &__restrict__ block,
};
}
// Unescaped quote
case '"':
block[0] = '\\';
block[1] = '"';
return u64x2
// Escape sequence case
assert(block[0] == '\\');
// Legitimately escaped sequence bank
const u8x16 cases
{
1, 2
'b', 't', 'n', 'f', 'r', '"', '\\', 'u'
};
// Escape sequence
case '\\': switch(block[1] & block_mask[1])
const u8x16 subject
{
simd::broad_cast(block, block[1]) &
simd::broad_cast(block_mask, block_mask[1])
};
const u8x16 match
(
subject == cases
);
const u64 match_depth
{
simd::clz(u64x2(match)) / 8
};
// Legitimately escaped single char
if(match_depth < 7)
{
// Legitimately escaped single chars
case '\\':
case '"':
case 'b':
case 't':
case 'n':
case 'f':
case 'r':
block[0] = '\\';
block[1] = block[1];
return u64x2
{
2, 2
};
case 'u': // Possible utf-16 surrogate(s)
return string_stringify_utf16(block, block_mask);
}
// Unnecessary escape; unless it's the last char.
default:
if(match_depth > 7)
{
block[0] = '\\';
block[1] = '\\';
return u64x2
{
1, block_mask[1]? 0UL: 2UL
};
};
}
// Possible utf-16 surrogate(s)
assert(block[1] == 'u');
return string_stringify_utf16(block, block_mask);
}
ircd::u64x2
@ -3610,6 +3623,8 @@ ircd::u64x2
ircd::json::string_serialized(const u8x16 block,
const u8x16 block_mask)
{
assert(block_mask[0] == 0xff);
const u8x16 is_esc
(
block == '\\'
@ -3643,54 +3658,59 @@ ircd::json::string_serialized(const u8x16 block,
regular_prefix_count, regular_prefix_count,
};
// Slow-path; decide what to do based on the next character.
switch(block[0])
{
// Covers the ctrl 0x00-0x20 range only; no other character here.
default:
{
assert(block[0] < 0x20);
#if __has_builtin(__builtin_assume)
__builtin_assume(block[0] < 0x20);
#endif
return string_serialized_ctrl(block, block_mask, is_ctrl);
}
// Unescaped quote: +1
case '"':
if(is_quote[0])
return u64x2
{
1, 2
};
// Covers the ctrl 0x00-0x20 range only; no other character here.
if(is_ctrl[0])
return string_serialized_ctrl(block, block_mask, is_ctrl);
// Escape sequence
case '\\': switch(block[1] & block_mask[1])
assert(block[0] == '\\');
// Legitimate escape bank
const u8x16 cases
{
// Legitimately escaped single chars
case '\\':
case '"':
case 'b':
case 't':
case 'n':
case 'f':
case 'r':
'b', 't', 'n', 'f', 'r', '"', '\\', 'u'
};
const u8x16 subject
{
simd::broad_cast(block, block[1]) &
simd::broad_cast(block_mask, block_mask[1])
};
const u8x16 match
(
subject == cases
);
const u64 match_depth
{
simd::clz(u64x2(match)) / 8
};
// Legitimately escaped single char
if(match_depth < 7)
return u64x2
{
2, 2
};
case 'u': // Possible utf-16 surrogate(s)
return string_serialized_utf16(block, block_mask);
// Unnecessary escape; unless it's the last char: -1
default:
if(match_depth > 7)
return u64x2
{
1, block_mask[1]? 0UL: 2UL
};
};
}
// Possible utf-16 surrogate(s)
assert(block[1] == 'u');
return string_serialized_utf16(block, block_mask);
}
ircd::u64x2