blake2: add Cargo feature to optimize for code size. #440
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The implementation uses some
inline(always)
to force inline theround
andquarter_round
functions for performance. This PR adds an opt-in Cargo feature to disable them, to allow optimizing for size instead.Building for
thumbv6m-none-eabi
:size_opt
disabled: 5772 bytessize_opt
enabled: 2372 bytesThis saves 3.4kb of code size, which is 60%.
I'm trying to use blake2 on a microcontroller with 32kb of Flash memory (where the code is stored), so saving 3.4kb is quite substantial.