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Python: Test demonstrating the need for phi-read-nodes #14858

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merged 2 commits into from
Nov 21, 2023
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Python: Test demonstrating the need for phi-read-nodes #14858

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Python: Test demonstrating need for phi-read-nodes
yoff Nov 21, 2023
077e51c
Python: fix test output
yoff Nov 21, 2023
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36 changes: 36 additions & 0 deletions python/ql/test/experimental/dataflow/use-use-flow/read_explosion.py
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Original file line number Diff line number Diff line change
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# This test file is inspired by
# `csharp/ql/test/library-tests/dataflow/local/UseUseExplosion.cs`
# but with `n=3` kept small, since we do have the explosion.

cond = ...

# global variables are slightly special,
# so we go into a function scope
def scope():
x = 0

if(cond > 3):
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You could also add a test for normal phi nodes, i.e. something like

    if(cond > 3):
      if(cond > 2):
        if(cond > 1):
           pass
        else:
          x = 1
      else:
        x = 2
    else:
      x = 3

    if(cond > 3):
      if(cond > 2):
        if(cond > 1):
           pass
        else:
          use(x)
      else:
        use(x)
    else:
      use(x)

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I put that in #14861. (Looks like I came to the exact same example :-))

if(cond > 2):
if(cond > 1):
pass
else:
use(x)
else:
use(x)
else:
use(x)

if(cond > 3):
if(cond > 2):
if(cond > 1):
pass
else:
use(x)
else:
use(x)
else:
use(x)

def use(v):
# this could just be `pass` but we do not want it optimized away.
y = v+2
24 changes: 24 additions & 0 deletions python/ql/test/experimental/dataflow/use-use-flow/use-use-counts.expected
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implicit_use_count
| 0 |
implicit_use
source_use_count
| 6 |
source_use
| read_explosion.py:17:15:17:15 | ControlFlowNode for x |
| read_explosion.py:19:13:19:13 | ControlFlowNode for x |
| read_explosion.py:21:11:21:11 | ControlFlowNode for x |
| read_explosion.py:28:15:28:15 | ControlFlowNode for x |
| read_explosion.py:30:13:30:13 | ControlFlowNode for x |
| read_explosion.py:32:11:32:11 | ControlFlowNode for x |
use_use_edge_count
| 9 |
use_use_edge
| read_explosion.py:17:15:17:15 | ControlFlowNode for x | read_explosion.py:28:15:28:15 | ControlFlowNode for x |
| read_explosion.py:17:15:17:15 | ControlFlowNode for x | read_explosion.py:30:13:30:13 | ControlFlowNode for x |
| read_explosion.py:17:15:17:15 | ControlFlowNode for x | read_explosion.py:32:11:32:11 | ControlFlowNode for x |
| read_explosion.py:19:13:19:13 | ControlFlowNode for x | read_explosion.py:28:15:28:15 | ControlFlowNode for x |
| read_explosion.py:19:13:19:13 | ControlFlowNode for x | read_explosion.py:30:13:30:13 | ControlFlowNode for x |
| read_explosion.py:19:13:19:13 | ControlFlowNode for x | read_explosion.py:32:11:32:11 | ControlFlowNode for x |
| read_explosion.py:21:11:21:11 | ControlFlowNode for x | read_explosion.py:28:15:28:15 | ControlFlowNode for x |
| read_explosion.py:21:11:21:11 | ControlFlowNode for x | read_explosion.py:30:13:30:13 | ControlFlowNode for x |
| read_explosion.py:21:11:21:11 | ControlFlowNode for x | read_explosion.py:32:11:32:11 | ControlFlowNode for x |
37 changes: 37 additions & 0 deletions python/ql/test/experimental/dataflow/use-use-flow/use-use-counts.ql
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import python
private import semmle.python.dataflow.new.internal.DataFlowPrivate

query int implicit_use_count() {
exists(SsaSourceVariable x | x.getName() = "x" | result = count(x.getAnImplicitUse()))
}

query ControlFlowNode implicit_use() {
exists(SsaSourceVariable x | x.getName() = "x" | result = x.getAnImplicitUse())
}

query int source_use_count() {
exists(SsaSourceVariable x | x.getName() = "x" | result = count(x.getASourceUse()))
}

query ControlFlowNode source_use() {
exists(SsaSourceVariable x | x.getName() = "x" | result = x.getASourceUse())
}

query int use_use_edge_count() {
exists(SsaSourceVariable x | x.getName() = "x" |
result =
count(NameNode use1, NameNode use2 |
use1 = x.getAUse() and
use2 = x.getAUse() and
LocalFlow::useToNextUse(use1, use2)
)
)
}

query predicate use_use_edge(NameNode use1, NameNode use2) {
exists(SsaSourceVariable x | x.getName() = "x" |
use1 = x.getAUse() and
use2 = x.getAUse() and
LocalFlow::useToNextUse(use1, use2)
)
}