[PATCH] D140035: [X86] Prevent -mibt-seal to work together with -flto=thin

[Sami Tolvanen via Phabricator via cfe-commits]

samitolvanen added a comment.

In D140035#3995703 <https://reviews.llvm.org/D140035#3995703>, @joaomoreira wrote:

> Regarding https://github.com/ClangBuiltLinux/linux/issues/1737:
>
> Weirdly enough, I double-tested the behavior for -flto=thin + -mibt-seal; the kernel did boot fine on my setup, but when dumped/grep'ed for ENDBRs, it had ~500 less ENDBRs throughout the binary. Considering that LTO-based optimizations applied with -flto=thin should have also been applied with -flto (which means, things like dead-code elimination should be symmetrical in both generated binaries), and also given the confirmation that -flto=thin won't properly keep address-taken details across translation units, my understanding is that -mibt-seal must be disabled when -flto=thin. Thus, submitted the patch even though I was not able to reproduce the bad behavior.




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