[PATCH] D84220: [IPSCCP] Fix a bug that the "returned" attribute is not cleared when function is optimized to return undef

Thu Jul 30 17:23:52 PDT 2020

jdoerfert added a comment.

In D84220#2185949 <https://reviews.llvm.org/D84220#2185949>, @congzhe wrote:

> Regarding the semantics of the "returned" attribute: I am very interested in your above-mentioned discussions on the semantics of the "returned" attribute, to be honest however, I did not quite follow and understand them. Would you please clarify them a little bit more, like what do you think should be the correct and incorrect semantics of "returned" ? Thank you!

The question is if "violating" returned is UB or something else. I generally think attribute violations should not result in UB (in most cases). My proposal is that you get the argument or `poison`, though, for now we stick to the former and modify the IPO passes that replace the return values.

Repository:
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  https://reviews.llvm.org/D84220/new/

https://reviews.llvm.org/D84220