On Mon, Feb 02, 2026 at 04:16:39PM +0100, Florian Weimer wrote:
> * Qing Zhao:
>
> > Our internal customer is asking for this feature.
> >
> > They used icc currently, with icc, then can get inline list, prof_used
> > list, etc. from the binary.
> >
> > The old studio compiler also provided such feature, there was compiler
> > commentary section in the binary to record many of the important
> > compiler transformations along with the line number information.
> >
> > If there is any performance issue with the application, such
> > information will be very useful. Especially for large applications.
>
> We have similar needs and use annobin for that. Its optimization
> coverage is not great, though. I think for guiding future GCC
> development, it would be really interesting to know how many (e.g.)
> memcpy calls are there because the source code was not built with source
> fortification, or because it was and the compiler deemed the call to be
> statically safe and not needing bounds checking, or it didn't have any
> bounds information at all, so checking was impossible. That part at
> least intersects with the desire to track certain optimization
> decisions.
Part of that is already available in debug info.
If you look to debug info corresponding to memcpy calls (sure, that won't
cover cases where memcpy has been expanded inline), if they are in
DW_TAG_inlined_subroutine for the bits/string_fortified.h inline, then
it has been -D_FORTIFY_SOURCE={2,3} protected, if not, then it has not.
Just we don't record anywhere whether gimple_fold_builtin_memory_chk decided
to fold __builtin___memcpy_chk to __builtin_memcpy because the last
argument wasn't all ones and the length argument was guaranteed to be
smaller than that, or if it was because the objsz pass determined the
last argument is all ones and so we can't protect it.
That said, all this is complicated by jump threading, inlining, unrolling
and other optimizations that can result in one source memcpy call to be
changed into multiple calls in the IL (or on the other side DCE etc. which
can remove some calls).
So, dunno what you want to track exactly, key stuff on the locations of the
memcpy (if extern inline memcpy then its caller) and track for each location
how many cases were folded because of all ones objsz, how many because of
gimple_fold_builtin_memory_chk etc.?
Jakub
