Remove tzcnt from audited BMI1 instructions
#1380
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As it turns out [^1], compilers will emit this instruction in some circumstances even when BMI1 is not technically available on your architecture, since by happy-accident older CPU's decode this instruction in backward-compatible way for non-zero inputs. [^1]: https://stackoverflow.com/questions/61422827/does-x64-support-imply-bmi1-support
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It'd be better to update the script https://github.com/JuliaPackaging/BinaryBuilder.jl/blob/2a5e7117be9ade099cd1092e7a444bdcffc37500/contrib/generate_instructions_list.jl which generates that file, otherwise this change risks of being overwritten. |
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By happy-accident, older CPU's decode this instruction in a backwards-compatible way for non-zero inputs 1, so it can be used even without feature support. In fact, compilers will emit this instruction in some circumstances even when BMI1 is not technically available on your architecture.
I hit this on JuliaPackaging/Yggdrasil#11124
Footnotes
https://stackoverflow.com/questions/61422827/does-x64-support-imply-bmi1-support ↩