[llvm-bugs] [Bug 27498] clang emits memcpy for std::swap, which can introduce undefined behavior

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=27498

whitequark <whitequark at whitequark.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|DUPLICATE                   |---

--- Comment #2 from whitequark <whitequark at whitequark.org> ---
Sorry but I am reopening this. Specifically because the generated IR violates
LLVM's own invariats! To quote LangRef for @llvm.memcpy: "The ‘llvm.memcpy.*‘
intrinsics copy a block of memory from the source location to the destination
location, which are not allowed to overlap."
http://llvm.org/docs/LangRef.html#id407

It might be that the fix is adjusting the contract of @llvm.memcpy--it is not
my call. But I would say that the current self-contradictory behavior is
indefensible.

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