From `pritomrajkhowa/LoopBound`:
```
Definitions.ql-7:PointsTo::InterProceduralPointsTo::callsite_points_to#ffff#join_rhs#3 ........... 5m53s
```
specifically
```
(767s) Tuple counts for PointsTo::InterProceduralPointsTo::callsite_points_to#ffff#join_rhs#3/3@f8f86764 after 5m53s:
832806293 ~0% {4} r1 = JOIN PointsTo::InterProceduralPointsTo::callsite_points_to#ffff#shared#1 WITH PointsTo::InterProceduralPointsTo::var_at_exit#fff ON FIRST 1 OUTPUT Lhs.0, Lhs.1 'arg1', Rhs.1 'arg2', Rhs.2 'arg0'
832806293 ~0% {3} r2 = JOIN r1 WITH Essa::TEssaNodeRefinement#ffff_03#join_rhs ON FIRST 2 OUTPUT Lhs.3 'arg0', Lhs.1 'arg1', Lhs.2 'arg2'
return r2
```
This one is a bit tricky to unpack. Where is this `shared#1` defined?
```
EVALUATE NONRECURSIVE RELATION:
SYNTHETIC PointsTo::InterProceduralPointsTo::callsite_points_to#ffff#shared#1(int arg0, numbered_tuple arg1) :-
SENTINEL PointsTo::InterProceduralPointsTo::callsite_points_to#ffff#shared
SENTINEL Definitions::EscapingAssignmentGlobalVariable#class#f
SENTINEL Essa::TEssaNodeRefinement#ffff_03#join_rhs
{2} r1 = JOIN PointsTo::InterProceduralPointsTo::callsite_points_to#ffff#shared WITH Definitions::EscapingAssignmentGlobalVariable#class#f ON FIRST 1 OUTPUT Lhs.0 'arg0', Lhs.1 'arg1'
{2} r2 = STREAM DEDUP r1
{2} r3 = JOIN r2 WITH Essa::TEssaNodeRefinement#ffff_03#join_rhs ON FIRST 2 OUTPUT Lhs.0 'arg0', Lhs.1 'arg1'
{2} r4 = STREAM DEDUP r3
return r4
```
Looking at `callsite_points_to`, we see a likely candidate in `srcvar`.
It is guarded with an `instanceof` check for
`EscapingAssignmentGlobalVariable` (which lines up nicely with the
sentinel on its charpred) and `getSourceVariable` is just a projection
of `TEssaNodeRefinement`.
So let's try unbinding `srcvar` to prevent an early join.
The timing is now:
```
Definitions.ql-7:PointsTo::InterProceduralPointsTo::callsite_points_to#ffff ...................... 31.3s (2554 evaluations with max 101ms in PointsTo::InterProceduralPointsTo::callsite_points_to#ffff/4@i516#581fap5w)
```
(Showing the tuple counts doesn't make sense here, since all of the
`shared` and `join_rhs` predicates have been smooshed around.)
Empty StmtSequences appear, for example, in the `else` branch of `if`
statements like the following:
foo
if cond
bar
else
end
baz
Before this change, the CFG for this code would look like this:
foo
│
│
▼
cond
│
true │
▼
bar
│
│
▼
if
│
│
▼
baz
i.e. there is linear flow through the condition, the `then` branch, and
out of the if. This doesn't account for the possibility that the
condition is false and `bar` is not executed. After this change, the CFG
looks like this:
foo
│
│
▼
cond
│ │
true │ │ false
▼ │
bar │
│ │
│ │
▼ ▼
if
│
│
▼
baz
i.e. we correctly account for the `false` condition.
