| Issue |
208761
|
| Summary |
[docs] Please include `select`'s semantics around `poison` in LangRef
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
scottmcm
|
As we were trying to figure out the problem that eventually led to filing #208611, a [bunch of people](https://rust-lang.zulipchat.com/#narrow/channel/131828-t-compiler/topic/Miscompilation.20in.201.2E97.2E0.20with.20new.20Option.3A.3ANone.20discriminant/near/609404638) (me included!) had uncertainty around whether or not the LLVM middle-end IR we were looking at was UB or not.
Notably, <https://llvm.org/docs/LangRef.html#select-instruction> doesn't mention anything about `poison` (nor `undef`) today, making it non-obvious how to resolve this uncertainty.
It turns out there's text about this in <https://llvm.org/docs/UndefinedBehavior.html#propagation-of-poison-through-select>, so at least linking from LangRef to that would be helpful. I personally never found that until someone else linked it directly.
![]()
_______________________________________________
llvm-bugs mailing list
[email protected]
https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-bugs
