[PATCH] D96349: [instcombine] Exploit UB implied by nofree attributes

[Philip Reames via Phabricator via llvm-commits]

reames added a comment.

In D96349#2551984 <https://reviews.llvm.org/D96349#2551984>, @jdoerfert wrote:

> LGTM. We should probably add the following negative test case:
>
>   ; Freeing in a nonfree function is fine if the effect is invisible to the outside
>   define void @test16() nofree {
>     i8* %foo = call i8* @malloc(i32 1)
>     call void @free(i8* %foo)
>     ret void
>   }

Er, no.  That's not okay.  Either by the implementation in this patch, or by my reading of the LangRef.  The langref says "This function attribute indicates that the function does not, directly or indirectly, call a memory-deallocation function (free, for example). "  There's no exception there for memory allocated in scope, nor should there be.


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https://reviews.llvm.org/D96349