clang: Tokenize more lazily. #1466
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Instead of converting all the tokens to utf-8 before-hand, which is costly, and allocating a new vector unconditionally (on top of the one clang already allocates), just do the tokenization more lazily. There's actually only one place in the codebase which needs the utf-8 string, all the others can just work with the byte slice from clang. This should have no behavior change, other than be faster. In particular, this halves the time on my machine spent on the test-case from rust-lang#1465. I'm not completely sure that this is going to be enough to make it acceptable, but we should probably do it regardless.
MihirLuthra
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Although, bindgen needs .enable_function_attribute_detection() to process __attribute__((__warn_unused_result__)) because parsing attrs can be really slow in certain cases. Benches were performed to confirm our case doesn't face that issue. References: rust-lang/rust-bindgen#2149 rust-lang/rust-bindgen#1465 rust-lang/rust-bindgen#1466 rust-lang/rust-bindgen#1467
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Instead of converting all the tokens to utf-8 before-hand, which is costly, and
allocating a new vector unconditionally (on top of the one clang already
allocates), just do the tokenization more lazily.
There's actually only one place in the codebase which needs the utf-8 string,
all the others can just work with the byte slice from clang.
This should have no behavior change, other than be faster. In particular, this
halves the time on my machine spent on the test-case from #1465.
I'm not completely sure that this is going to be enough to make it acceptable,
but we should probably do it regardless.