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[Switch variable detection] No switch variable candidate found #339

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[Switch variable detection] No switch variable candidate found #339

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de60b8c
Create draft PR for #217
mm4rks Sep 17, 2023
f036f96
allow switching on undefined variables. If all previous stages are
mm4rks Sep 17, 2023
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8 changes: 8 additions & 0 deletions decompiler/pipeline/preprocessing/switch_variable_detection.py
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Original file line number Diff line number Diff line change
@@ -1,4 +1,5 @@
"""Module for finding variable relevant to switch"""
import pysnooper
from typing import Optional

from decompiler.pipeline.stage import PipelineStage
Expand All @@ -8,6 +9,7 @@
from decompiler.structures.pseudo.instructions import Assignment, Branch, IndirectBranch, Instruction
from decompiler.structures.pseudo.operations import Condition, OperationType, UnaryOperation
from decompiler.task import DecompilerTask
from decompiler.util.decoration import DecoratedCFG


def is_dereference(expression: Expression) -> bool:
Expand Down Expand Up @@ -72,6 +74,7 @@ def __init__(self):
self._def_map: DefMap
self._use_map: UseMap
self._dereferences_used_in_branches: set
self._undefined_variables: set

def run(self, task: DecompilerTask):
"""
Expand All @@ -87,6 +90,8 @@ def run(self, task: DecompilerTask):
Overcomes issues with dummy heuristic.
"""
self._init_map(task.graph)
self._undefined_variables = task.graph.get_undefined_variables()
# DecoratedCFG.from_cfg(task.graph).export_plot("switch.png")
for switch_block in {edge.source for edge in task.graph.edges if isinstance(edge, SwitchCase)}:
self._handle_switch_block(switch_block)

Expand All @@ -106,6 +111,7 @@ def _handle_switch_block(self, basic_block: BasicBlock):
switch_expression = self.find_switch_expression(switch_instruction)
switch_instruction.substitute(switch_instruction.expression, switch_expression)

@pysnooper.snoop()
def find_switch_expression(self, switch_instruction: Instruction):
"""Try to deduce the variable utilized for the switch instruction."""
traced_variable = (
Expand Down Expand Up @@ -153,6 +159,7 @@ def _is_copy_assigned(self, value: Variable) -> bool:
return isinstance(definition.value, Variable)
return False


def _is_bounds_checked(self, value: Variable) -> bool:
"""
Check if variable can be used in switch expression.
Expand All @@ -163,6 +170,7 @@ def _is_bounds_checked(self, value: Variable) -> bool:
self._is_used_in_condition_assignment(value),
self._is_used_in_branch(value),
self._is_predecessor_dereferenced_in_branch(value),
value in self._undefined_variables,
]
)

Expand Down