winch: Properly zero extend the CAS result#12994
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saulecabrera merged 1 commit intobytecodealliance:mainfrom Apr 10, 2026
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winch: Properly zero extend the CAS result#12994saulecabrera merged 1 commit intobytecodealliance:mainfrom
saulecabrera merged 1 commit intobytecodealliance:mainfrom
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Manually removing from queue due to failure at https://github.com/bytecodealliance/wasmtime/actions/runs/24209086212/job/70672712892 |
Accoding to the spec, the result of a compare-and-swap operation must be zero extended according to the result type. Prior to this commit the implementation was skipping the 32 -> 64 bit case. When the swap happens, the value in `rax` remains untouched, however, it's possible that the higher bits are undefined, in which case the zero extension is needed to ensure that the right value is returned. This bug is only reproducible for values in which the lower bits match the expected value, like in the example included in this commit.
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Ok, I've fixed the issues. I'll re-add to the queue. |
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Accoding to the spec, the result of a compare-and-swap operation must be zero extended according to the result type. Prior to this commit the implementation was skipping the 32 -> 64 bit case.
When the swap happens, the value in
raxremains untouched, however, it's possible that the higher bits are undefined, in which case the zero extension is needed to ensure that the right value is returned.This bug is only reproducible for values in which the lower bits match the expected value, like in the example included in this commit.