On Wed, 29 Jan 2025 16:30:46 GMT, Shaojin Wen <s...@openjdk.org> wrote:
>> This is an optimization for decimal Integer.parseInt and Long.parseLong, >> which improves performance by about 10%. The optimization includes: >> 1. Improve performance by parsing 2 numbers at a time, which has performance >> improvements for numbers with length >= 3. >> 2. It uses charAt(0) for the first number. Assuming that the optimization >> can eliminate boundary checks, this will be more friendly to parsing numbers >> with length 1. >> 3. It removes the reliance on the Character.digit method and eliminates the >> reliance on the CharacterDataLatin1#DIGITS cache array, which avoids >> performance degradation caused by cache misses. > > Shaojin Wen has updated the pull request incrementally with one additional > commit since the last revision: > > copyright src/java.base/share/classes/jdk/internal/util/DecimalDigits.java line 181: > 179: return -1; > 180: } > 181: return ((d & 0xF) << 3) + ((d & 0xF) << 1) // (d & 0xF) * 10 Is simply using `(d & 0xF) * 10` any worse? I expect the compiler knows this trick and would use it when appropriate. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/22919#discussion_r1934408496
