Summary:
This diff tries to support a specific form of linked list iteration in Java.
```
while (p != null) {
p = p.getNext();
}
```
This example was a constant cost before because the cost checker could not detect that it is an iteration on a linked list.
The heuristic this diff implemented is:
(1) `p = p.getNext()`: It tries to find this specific form of assignment. Then, it increments `p.linked_list_index` by 1. Note that `linked_list_index` is a virtual field for keeping an index in the linked list. Its initial value is always 0.
(2) At `p != null`, it tries to prune the value of `p.linked_list_index`: the upper-bound of `p.linked_list_index` is pruned by `<= p.linked_list_length`. Here again, `p.linked_list_length` is also a virtual field to denote the length of the linked list.
Reviewed By: ezgicicek
Differential Revision: D22234892
fbshipit-source-id: 2fee176bb
Summary:
The zero cost of node does not make sense especially when the abstract memory is non-bottom. This
resulted in unreasonable zero cost results sometimes, e.g. when the checker could not find
appropriate control varaibles having interval values of iteration. This diff fixes this, so sets
the minimum basic cost as 1, if the abstract memory at the node is non-bottom.
Reviewed By: ezgicicek
Differential Revision: D18199291
fbshipit-source-id: b215d10e5
Summary:
`ModeledRange` represents how many times the interval value can be updated by modeled functions. This
domain is to support the case where there are mismatches between value of a control variable and
actual number of loop iterations. For example,
```
while((c = file_channel.read(buf)) != -1) { ... }
```
the loop will iterates as the file size, but the control variable `c` does not have that value. In
these cases, it assigns a symbolic value of the file size to the modeled range of `c`, then which
is used when calculating the overall cost.
Reviewed By: jvillard
Differential Revision: D17476621
fbshipit-source-id: 9a81376e8
Sungkeun Cho
Ezgi Çiçek
Josh Berdine
Mehdi Bouaziz