Re: sparse-llvm incorrect definition of local variables

[Dibyendu Majumdar <mobile@majumdar.org.uk>]

Hi Luc,

On 8 March 2017 at 06:53, Luc Van Oostenryck
<luc.vanoostenryck@gmail.com> wrote:
> On Tue, Mar 07, 2017 at 07:31:34AM +0000, Dibyendu Majumdar wrote:
>> >> Here 'values' has been defined above as external global, whereas it
>> >> should be allocated on the stack.
>> >
>> > Mmmh, I'll need to look a bit further at this one.
>> >
>>
>> It appears that sparse-llvm only creates a local stack object for each
>> OP_PHI instruction. What should be the general approach for
>> identifying local stack objects in sparse linearized output?
>
> I've looked a bit at this and there is several issues at hand.
> It's also not something LLVM specific.
> So I can't answer to this for now. Hopefully, I'll be able to tell
> you more in a few days.
>

Thank you for looking into this. It would be good to know what issues
you have discovered. I was wondering if a simple solution is to check
whether the symbol is marked  as toplevel / extern - and if not then
define it as a local symbol in LLVM. However we would need to handle
scope - i.e. if the same symbol occurs multiple times in a function in
different scopes then these need to be defined accordingly. Example:

extern void init(int *v);
int main(const char *argv[]) {
 int n = 0;
 {
  int x[5];
  init(x);
  n += x[0];
 }
 {
  int x[6];
  init(x);
  n += x[0];
 }
 return n;
}

Regards
Dibyendu