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Replace TODOs with comments about why we DIDNTDO

This commit is contained in:
John Keiser 2020-07-01 10:31:10 -07:00
parent d3c089130d
commit 7a9f6b48f4
1 changed files with 8 additions and 4 deletions
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12
src/generic/stage2/numberparsing.h
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@ -358,9 +358,10 @@ really_inline bool write_float(const uint8_t *const src, bool negative, uint64_t
return success;
}
}
// TODO unlikely wraps the wrong thing here
if (unlikely(exponent < FASTFLOAT_SMALLEST_POWER) ||
(exponent > FASTFLOAT_LARGEST_POWER)) { // this is uncommon!!!
// NOTE: it's weird that the unlikely() only wraps half the if, but it seems to get slower any other
// way we've tried: https://github.com/simdjson/simdjson/pull/990#discussion_r448497331
// To future reader: we'd love if someone found a better way, or at least could explain this result!
if (unlikely(exponent < FASTFLOAT_SMALLEST_POWER) || (exponent > FASTFLOAT_LARGEST_POWER)) {
// this is almost never going to get called!!!
// we start anew, going slowly!!!
bool success = slow_float_parsing((const char *) src, writer);
@ -403,7 +404,6 @@ really_inline bool parse_number(UNUSED const uint8_t *const src,
++p;
negative = true;
// a negative sign must be followed by an integer
// TODO this is a redundant check
if (!is_integer(*p)) { return INVALID_NUMBER(src); }
}
const char *const start_digits = p;
@ -414,6 +414,10 @@ really_inline bool parse_number(UNUSED const uint8_t *const src,
if (is_integer(*p)) { return INVALID_NUMBER(src); } // 0 cannot be followed by an integer
i = 0;
} else {
// NOTE: This is a redundant check--either we're negative, in which case we checked whether this
// is a digit above, or the caller already determined we start with a digit. But removing this
// check seems to make things slower: https://github.com/simdjson/simdjson/pull/990#discussion_r448512448
// Please do try yourself, or think of ways to explain it--we'd love to understand :)
if (!is_integer(*p)) { return INVALID_NUMBER(src); } // must start with an integer
unsigned char digit = static_cast<unsigned char>(*p - '0');
i = digit;