Re: [PATCH v2 00/10] Introduce strub: machine-independent stack scrubbing

[Richard Biener <richard.guenther@gmail.com>]

On Tue, Oct 11, 2022 at 3:33 PM Alexandre Oliva <oliva@adacore.com> wrote:
>
> On Oct 11, 2022, Richard Biener <richard.guenther@gmail.com> wrote:
>
> > On Tue, Oct 11, 2022 at 1:57 PM Alexandre Oliva <oliva@adacore.com> wrote:
> >>
> >> On Oct 10, 2022, Richard Biener <richard.guenther@gmail.com> wrote:
> >>
> >> > As noted in the Cauldron Discussion I think you should do all
> >> > instrumentation post-IPA only to simplify your life not needing to
> >> > handle inlining of instrumentation
> >>
> >> I looked a bit into that after the Cauldron, and recalled why I wanted
> >> to instrument before inlining: in the case of internal strub, that
> >> introduces a wrapper, it's desirable to be able to inline the wrapper.
>
> > I think if the wrapper is created at IPA time it is also available for
> > IPA inlining.
>
> Yeah, but now I'm not sure what you're suggesting.  The wrapper is
> instrumentation, and requires instrumentation of the wrapped
> counterpart, so that can't be post-IPA.

IPA folks can probably explain better but there's IPA (local)
analysis, IPA (global) propagation
and IPA (local) code generation.  You'd instrument (and actually
create the wrappers)
at IPA code generation time but virtually the wrapper would become existent
somewhen during IPA propagation by means of a clone to be materialized
(I understand the wrapper is something like a thunk).  The IPA
propagation phase would
decide which calls should go to the wrapper (and instrumented
function) and which
can use the original uninstrumented function (maybe from local already
strubbed functions).

Richard.

>
> --
> Alexandre Oliva, happy hacker                https://FSFLA.org/blogs/lxo/
>    Free Software Activist                       GNU Toolchain Engineer
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