Return the original value in Interlocked.Or/And #33102
Conversation
tannergooding
left a comment
tannergooding
left a comment
There was a problem hiding this comment.
LGTM.
Seems a bit unfortunate that whether the new or original value is returned differs based on the operation, but this does match what the Windows interlocked APIs are doing. It looks to also match what ARM64 encodes for their atomic instructions, but not quite what x86 does (outside the special "XADD - Exchange and Add" instruction).
|
I find it a bit confusing honestly. |
That's why I did it as the new value initially, for consistency with Add. But with Add, you can always compute the original value from the new value; that's not the case for And and Or. |
These APIs were introduced recently in dotnet/runtime#33042 and already used in several places e.g. in `Task`, `InterlockedBitVector32`, `SafeHandle`, `RegexCharClass` It should emit `%reg = atomicrmw and (or)` in LLVM IR. (and unlike `Interlocked.Add` these API return old value, see dotnet/runtime#33102 Addresses dotnet/runtime#32239 for Mono.
These APIs were introduced recently in dotnet/runtime#33042 and already used in several places e.g. in `Task`, `InterlockedBitVector32`, `SafeHandle`, `RegexCharClass` It should emit `%reg = atomicrmw and (or)` in LLVM IR. (and unlike `Interlocked.Add` these API return old value, see dotnet/runtime#33102 Addresses dotnet/runtime#32239 for Mono. Co-authored-by: EgorBo <EgorBo@users.noreply.github.com>
ghost
locked as resolved and limited conversation to collaborators
4 participants
From discussion in #33042 make
Interlocked.OrandInterlocked.Andreturn the original value instead of the updated one.There aren't yet any usages in libraries that look at the returned value.
cc: @jkotas, @GrabYourPitchforks, @tannergooding