[PATCH] D80791: [AArch64] Generate .note.gnu.property based on module flags.

[Szabolcs Nagy via Phabricator via cfe-commits]

nsz added a comment.

In D80791#2207203 <https://reviews.llvm.org/D80791#2207203>, @chill wrote:

> I would prefer to avoid the situation where the markings of two otherwise identical files were different,
> depending on how the files were produced, no matter if it was a common or a special case.

i don't see why it is desirable to silently get marking on an object file if function definitions happen to be bti compatible in it:

- compiler cannot reliably do this (e.g. bti incompatible inline asm).
- some users don't want the marking: not all linkers support it so it can cause unexpected breakage.
- most users (all?) want the marking reliably (not opportunistically), but function annotations are fragile (can depend on optimizations and code outside of user control).
- it is not useful to have a bti annotated function unless everything else is bti compatible too: it is all or nothing per elf module.
- but a compiler cannot diagnose if only some functions have the annotation (we don't have a cflag for it) so even if the compiler tried to add the marking silently users cannot rely on it: it's too easy to drop the marking and no way to debug such failure.


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https://reviews.llvm.org/D80791