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d-e-s-o
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As it turns out, the Rust compiler uses variable length LEB128 encoded integers internally. It so happens that they spent a fair amount of effort micro-optimizing the decoding functionality [0] [1], as it's in the hot path. With this change we replace our decoding routines with these optimized ones. To make that happen more easily (and to gain some base line speed up), also remove the "shift" return from the respective methods. As a result of these changes, we see a respectable speed up: System gimli-rs#1: Before: test bench_reading_leb128_unsigned ... bench: 235.83 ns/iter (+/- 32.53) After: test bench_reading_leb128_unsigned ... bench: 157.38 ns/iter (+/- 17.09) System gimli-rs#2: Before: test bench_reading_leb128_unsigned ... bench: 183.70 ns/iter (+/- 2.72) After: test bench_reading_leb128_unsigned ... bench: 109.08 ns/iter (+/- 3.11) [0] rust-lang/rust#69050 [1] rust-lang/rust#69157 Signed-off-by: Daniel Müller <deso@posteo.net>
d-e-s-o
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Sep 10, 2025
As it turns out, the Rust compiler uses variable length LEB128 encoded integers internally. It so happens that they spent a fair amount of effort micro-optimizing the decoding functionality [0] [1], as it's in the hot path. With this change we replace our decoding routines with these optimized ones. To make that happen more easily (and to gain some base line speed up), also remove the "shift" return from the respective methods. As a result of these changes, we see a respectable speed up: System gimli-rs#1: Before: test bench_reading_leb128_unsigned ... bench: 235.83 ns/iter (+/- 32.53) After: test bench_reading_leb128_unsigned ... bench: 157.38 ns/iter (+/- 17.09) System gimli-rs#2: Before: test bench_reading_leb128_unsigned ... bench: 183.70 ns/iter (+/- 2.72) After: test bench_reading_leb128_unsigned ... bench: 103.83 ns/iter (+/- 3.28) [0] rust-lang/rust#69050 [1] rust-lang/rust#69157 Signed-off-by: Daniel Müller <deso@posteo.net>
d-e-s-o
added a commit
to d-e-s-o/gimli
that referenced
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Sep 10, 2025
As it turns out, the Rust compiler uses variable length LEB128 encoded integers internally. It so happens that they spent a fair amount of effort micro-optimizing the decoding functionality [0] [1], as it's in the hot path. With this change we replace our decoding routines with these optimized ones. As a result of these changes, we see a respectable speed up: System gimli-rs#1: Before: test bench_reading_leb128_unsigned ... bench: 235.83 ns/iter (+/- 32.53) After: test bench_reading_leb128_unsigned ... bench: 157.38 ns/iter (+/- 17.09) System gimli-rs#2: Before: test bench_reading_leb128_unsigned ... bench: 183.70 ns/iter (+/- 2.72) After: test bench_reading_leb128_unsigned ... bench: 103.83 ns/iter (+/- 3.28) [0] rust-lang/rust#69050 [1] rust-lang/rust#69157 Signed-off-by: Daniel Müller <deso@posteo.net>
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I think DWARF 1 was different enough that it can't be parsed by a DWARF 2+ parser. So, reject it.