YJIT: Specialize String#[]
(String#slice
) with fixnum arguments
#12069
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String#[]
is in the top few C calls of several YJIT benchmarks:liquid-compile rubocop mail sudoku
While it has 5 different argument scenarios the most common by far are one fixnum and two fixnums
so we match those argument types and write the ccall directly to the corresponding C function.
This speeds up these benchmarks by 1-5%.
This is similar to the
String#byteslice
specialization #9939but it works harder to find the type info which was necessary for the specialization to apply in the large generated code of the
mail
gem.