Problem in understanding points-to analysis

[Nikhil Patil]

Hello everyone,

I am trying to understand the points-to analysis ("pta") ipa pass, but
I am not able to match the information generated by the pass and that
in structure "SSA_NAME_PTR_INFO".

For the code segment,

----------------------------------------------
int var1, var2, var3, var4, *ptr1, *ptr2, **ptr3;

if (var1==10) {
    ptr1 = &var1;
    ptr2 = &var2;
}
else {
    ptr1 = &var3;
    ptr2 = &var4;
}

if (var2==3) {
    ptr3 = &ptr1;
}
else {
    ptr3 = &ptr2;
}

printf("\n %d %d \n",*ptr1, **ptr3);
----------------------------------------------

The points-to information in dump_file of "pta" pass:
ptr1.2_6 = { var1 var3 }
ptr1 = { var1 var3 } same as ptr1.2_6

But accessing the structure "SSA_NAME_PTR_INFO" (using API
dump_points_to_info_for(..) ) in a pass AFTER "pta", shows
ptr1.2_6, points-to vars: { var1 var3 }
ptr1, points-to anything

Why here 'ptr1' is not pointing to '{ var1 var3 }' as found by "pta"?

Can someone please help me understand this behaviour?


--
Thanks,
Nikhil Patil.