SV: [PATCH] libgccjit: Add function to set the initial value of a global variable [PR96089]

[Antoni Boucher]

Le mardi 23 novembre 2021 à 10:51 +0000, Petter Tomner a écrit :
> Hi!
> 
> Does it work with pointers to other symbols and unions? I don't think
> constant symbols end
> up in the .rdata section unless they are marked for that.

Since I don't provide a constructor for unions, it doesn't work for
them.
I believe it works for an address of a global variable, but I can't
remember.

> 
> I did a similar patch that I just dropped in a RFC mail some time ago.
> (See attachment).

That looks indeed much more complete than my patch.
I'm gonna try your patch for rustc_codegen_gcc when I'm back from
vacation in December and tell you if it works or if it misses
something.
David, could you please take a look at Petter's patch?

> 
> If I remember correctly there need to be alot of folding to not
> segfault deeper into gcc on
> expressions that are not one literal, for e.g. pointer arithmetic.
> 
> Regards,
> Petter 
> 
> 
> Från: Gcc-patches <gcc-patches-bounces+tomner=kth.se@gcc.gnu.org> för
> Antoni Boucher via Gcc-patches <gcc-patches@gcc.gnu.org>
> Skickat: den 23 november 2021 03:01
> Till: David Malcolm
> Kopia: jit@gcc.gnu.org; gcc-patches@gcc.gnu.org
> Ämne: Re: [PATCH] libgccjit: Add function to set the initial value of a
> global variable [PR96089]
>     
> Hi David!
> 
> I updated the patch to allow initializing global variables with values
> of type array or struct.
> 
> I also fixed the bug I was talking in my previous message by using the
> following workaround: I create a new memento for the action of setting
> the global variable initial value and as such, both the global variable
> and the initial value are bound to exist when setting the global
> variable initializer.
> Is that workaround good enough?
> (I guess that workaround could be used to fix the same issue that we
> have for inline assembly.)
> 
> Thanks for the review!
> 
> Le vendredi 11 juin 2021 à 16:44 -0400, Antoni Boucher a écrit :
> > David: this one wasn't reviewed yet by you, so you can review it.
> > 
> > Le jeudi 20 mai 2021 à 21:27 -0400, Antoni Boucher a écrit :
> > > Hi.
> > > 
> > > I made this patch to set an arbitrary value to a global variable.
> > > 
> > > This patch suffers from the same issue as inline assembly
> > > (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100380), i.e. it
> > > segfaults if the `rvalue` is created after the global variable.
> > > It seems to be a design issue so I'm not sure what would be the fix
> > > for
> > > it and having it fixed would allow me to test this new function
> > > much
> > > more and see if things are missing (i.e. it might require a way to
> > > create a constant struct).
> > > See the link above for an explanation of this issue.
> > > 
> > > Thanks for the review.
> > 
> 
>