rnk added inline comments.
================
Comment at: include/clang/Basic/Attr.td:1494
+def NoStackProtector : InheritableAttr {
+ let Spellings = [GCC<"no_stack_protector">];
+ let Subjects = SubjectList<[Function]>;
----------------
aaron.ballman wrote:
> manojgupta wrote:
> > aaron.ballman wrote:
> > > This is not a GCC attribute, so this should use the Clang spelling.
> > >
> > > However, why spell the attribute this way rather than use the GCC
> > > spelling (`optimize("no-stack-protector")`?
> > Thanks, I have changed it to use Clang spelling.
> >
> > Regarding __attribute__((optimize("..."))), it is a generic facility in GCC
> > that works for many optimizer flags.
> > Clang currently does not support this syntax currently instead preferring
> > its own version for some options e.g. -O0.
> > e.g.
> > ```
> > __attribute__((optimize("O0"))) // clang version is
> > __attribute__((optnone))
> > ```
> > If we want to support the GCC syntax, future expectation would be support
> > more flags under this syntax. Is that the path we want to take (I do not
> > know the history related to previous syntax decisions but better GCC
> > compatibility will be a nice thing to have)
> The history of `optnone` predates my involvement with Clang and I've not been
> able to find the original review thread (I did find the one where I gave my
> LGTM on the original patch, but that was a resubmission after the original
> design was signed off).
>
> I'm not keen on attributes that have the same semantics but differ in
> spelling from attributes supported by GCC unless there's a good reason to
> deviate. Given that we've already deviated, I'd like to understand why better
> -- I don't want to push you to implement something we've already decided was
> a poor design, but I also don't want to accept code if we can instead use
> syntax that is compatible with GCC.
I do not think we want to pursue supporting generic optimization flags with
`__attribute__((optimize("...")))`.
Part of the reason we only support `optnone` is that LLVM's pass pipeline is
global to the entire module. It's not trivial to enable optimizations for a
single function, but it is much easier to have optimization passes skip
functions marked `optnone`.
Repository:
rC Clang
https://reviews.llvm.org/D46300
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