<bit>: fix countl_zero on arm64 - #2647
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Stephan T. Lavavej (StephanTLavavej) merged 3 commits intoApr 16, 2022
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Casey Carter (CaseyCarter)
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Casey Carter (CaseyCarter)
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Apr 11, 2022
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<bit>: fix countl_zero on arm64
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Did the buggy version make it into a release? |
Alex Guteniev (AlexGuteniev)
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Apr 12, 2022
Stephan T. Lavavej (StephanTLavavej)
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Apr 13, 2022
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Yes, this was introduced by #795 merged on 2020-07-01, shipped in VS 2019 16.8. |
Stephan T. Lavavej (StephanTLavavej)
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Apr 14, 2022
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Charlie Barto (@barcharcraz) Casey Carter (@CaseyCarter) I went ahead and pushed changes for the issue that Alex noticed, as we talked about it during the maintainer meeting. |
Casey Carter (CaseyCarter)
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Apr 14, 2022
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I'm mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed. |
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Thanks for finding and fixing this silent bad codegen! 🐞 🔍 ✅ |
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Fix countl_zero on arm64 to properly subtract the zeros resulting from widening.
Because of a lack of test coverage, we forgot that
_CountLeadingZerostakesunsigned long, and thus for types shorter than that we need to subtract the extra zeros from the result.