Duplicate constraints in ipa-pta

[Tom de Vries]

Richard,

when compiling this testcase:
...
static int __attribute__((noinline, noclone))
foo (int *a, int *b)
{
   *b = 1;
   *a = 2;
   return *b;
}

int __attribute__((noinline, noclone))
bar (int *a, int *b)
{
   return foo (a, b);
}
...

with -O2 -fipa-pta we find in the pta dumpfile:
...
Generating constraints for bar (bar)

bar.arg0 = &NONLOCAL
bar.arg1 = &NONLOCAL
bar.arg1 = &NONLOCAL
...

The reason for the duplicate last two constraints is that with fipa-pta, 
in create_function_info_for we link the function arguments in a next chain.

And in intra_create_variable_infos there are two iteration mechanism used:
- the loop over the function arguments
- the loop over the vi_next (p) for each function argument p

So when processing argument a, we generate constraints for both a and 
it's next b.
And when processing argument b, we generate constraints for b again.

Is this a known issue? Should we fix this?

Thanks,
- Tom