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Optimize decimal formatting of 128-bit integers ## Description This PR optimizes the `udivmod_1e19` function, which is used for formatting 128-bit integers, based on the algorithm provided in \[1\]. This optimization improves performance of formatting 128-bit integers, especially on 64-bit architectures. It also slightly reduces the output binary size. ## Assembler comparison https://godbolt.org/z/YrG5zY ## Performance #### previous results ``` test fmt::write_u128_max ... bench: 552 ns/iter (+/- 4) test fmt::write_u128_min ... bench: 125 ns/iter (+/- 2) ``` #### new results ``` test fmt::write_u128_max ... bench: 205 ns/iter (+/- 13) test fmt::write_u128_min ... bench: 129 ns/iter (+/- 5) ``` ## Reference \[1\] T. Granlund and P. Montgomery, “Division by Invariant Integers Using Multiplication” in Proc. of the SIGPLAN94 Conference on Programming Language Design and Implementation, 1994, pp. 61–72 |
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