Re: [PATCH] libgccjit: Fix get_size of size_t

[Antoni Boucher <bouanto@zoho.com>]

On Thu, 2023-12-07 at 19:57 -0500, David Malcolm wrote:
> On Thu, 2023-12-07 at 17:26 -0500, Antoni Boucher wrote:
> > Hi.
> > This patch fixes getting the size of size_t (bug 112910).
> > 
> > There's one issue with this patch: like every other feature that
> > checks
> > for target-specific stuff, it requires a compilation before
> > actually
> > fetching the size of the type.
> > Which means that getting the size before a compilation might be
> > wrong
> > (and I actually believe is wrong on x86-64).
> > 
> > I was wondering if we should always implicitely do the first
> > compilation to gather the correct info: this would fix this issue
> > and
> > all the others that we have due to that.
> > I'm not sure what would be the performance implication.
> 
> Maybe introduce a new class target_info which contains all the
> information we might want to find via a compilation, and have the
> top-
> level recording::context have a pointer to it, which starts as
> nullptr,
> but can be populated on-demand the first time something needs it?

That would mean that we'll need to populate it for every top-level
context, right? Would the idea be that we should then use child
contexts to have the proper information filled?
If so, how is this different than just compiling two contexts like what
I currently do?
This would also mean that we'll do an implicit compilation whenever we
use an API that needs this info, right? Wouldn't that be unexpected?

Thanks for the idea.

> 
> > 
> > Another solution that I have been thinking about for a while now
> > would
> > be to have another frontend libgccaot (I don't like that name),
> > which
> > is like libgccjit but removes the JIT part so that we get access to
> > the
> > target stuff directly and would remove the need for having a
> > seperation
> > between recording and playback as far as I understand.
> > That's a long-term solution, but I wanted to share the idea now and
> > gather your thoughts on that.
> 
> FWIW the initial version of libgccjit didn't have a split between
> recording and playback; instead the client code had to pass in a
> callback to call into the various API functions (creating tree
> nodes).
> See:
> https://gcc.gnu.org/legacy-ml/gcc-patches/2013-10/msg00228.html
> 
> Dave
>