[clang] [Clang] Set writable and dead_on_unwind attributes on sret arguments (PR #77116)

[Nikita Popov via cfe-commits]

nikic wrote:

Some IR for reference: https://clang.godbolt.org/z/qEsP7vozW I believe that on unwind, the sret temporary is either entirely unused (if no cleanup landingpad is necessary) or we will call lifetime.end on it (which is legal for dead_on_unwind). This should be independent of whether copy elision is performed or not.

https://github.com/llvm/llvm-project/pull/77116