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

[Szabolcs Nagy via Phabricator via llvm-commits]

nsz added a comment.

In D80791#2206933 <https://reviews.llvm.org/D80791#2206933>, @chill wrote:

> In D80791#2206853 <https://reviews.llvm.org/D80791#2206853>, @nsz wrote:
>
>> i think that cannot work.
>>
>> the implementation is free to inject arbitrary code into
>> user code so if the user does not tell the implementation
>> that it wants the entire tu to be bti safe then non-bti
>> code can end up in there. (e.g. ctor of an instrumentation
>> that is not realated to any particular function with the
>> bti marking)
>
> Certainly, there are cases it won't work, but there are definitely
> cases where it *can* work. Whatever the implementation does
> should be a deterministic consequence of implementing the relevant
> language standards together with implementation-defined behaviour,
> command-line options and language extensions (e..g attributes).
>
> Certainly I don't expect C++ ctorts/dtors in C code and gcov or
> sanitiser calls if I haven't given relevant `-fprofile-whatever`/`-fsanitize=whatever`
> options. In that sense, the implementation cannot do whatever
> it pleases, it is constrained to a range of behaviours one can reason about.

i think it's a bad idea to use function level
attributes to control what markings we attach to
translation units and i would prefer to only add
markings to object files when the compiler is
asked to do so per tu.

i dont want to see source code changes
to enable bti, that should be only needed
for some special case that's way out of
standard conform code.


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