[PATCH] D80911: AArch64+ARM: make LLVM consider system registers volatile to prevent unsound optimizations.

[Johannes Doerfert via Phabricator via llvm-commits]

jdoerfert added a comment.

As an alternative, and necessary regardless, we need to teach AA that "no-`nosync`" operations can experience the effects of external things. As long as `llvm.read_register` is not marked `nosync` that should prevent hoisting. Should, because AA doesn't know this yet. (https://bugs.llvm.org/show_bug.cgi?id=46210).

I do however see the potential for two intrinsics here, one that is a synchronizing read and one that is not. From that perspective this seems reasonable.


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https://reviews.llvm.org/D80911