Use NonZeroU64 to optimize encoded_len_varint
#1192
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The leading zeros count may perform better on many architectures when the zero case is excluded. Also use ilog2 as shorthand for the leading zeros trick because it makes more clearly what we mean to get, and should be ideally optimized by the compiler.
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Give the compiler all the leverage to optimize
encoded_len_varint:NonZeroU64to count leading zeros, as that can be faster on many platforms;ilog2instead of a handwritten expression to compute the base 2 algorithm, as the core library developers and the compiler would probably be in the best position to fine-tune it for all supported platforms.With the
varintbenchmarks, I see slight improvements (1-3%) or no reproducible performance changes on 11th gen Intel Core and Mac M3.