Fix:

- LocalIRVariable: remove dupplicate non_ssa_version assignment
SSA improvements (fix #156)
        - Add PHI operation on functions' arguments
        - Use reachable_from information to find the PHI rvalues

slither/slithir/utils/ssa.py

@@ -54,7 +54,12 @@ def add_ssa_ir(function, all_state_variables_instances):
         return
 
     init_definition = dict()
-    for v in function.parameters+function.returns:
+    for v in function.parameters:
+        if v.name:
+            init_definition[v.name] = (v, function.entry_point)
+            function.entry_point.add_ssa_ir(Phi(LocalIRVariable(v), set()))
+
+    for v in function.returns:
         if v.name:
             init_definition[v.name] = (v, function.entry_point)
 

slither/slithir/variables/local_variable.py

@@ -37,7 +37,6 @@ class LocalIRVariable(LocalVariable, SlithIRVariable):
             self._non_ssa_version = local_variable.non_ssa_version
         else:
             self._non_ssa_version = local_variable
-        self._non_ssa_version = local_variable
 
     @property
     def index(self):

slither/solc_parsing/declarations/function.py

@@ -28,6 +28,8 @@ from slither.visitors.expression.export_values import ExportValues
 from slither.visitors.expression.has_conditional import HasConditional
 from slither.core.declarations.contract import Contract
 
+from slither.slithir.variables import StateIRVariable, LocalIRVariable, Constant
+
 logger = logging.getLogger("FunctionSolc")
 
 class FunctionSolc(Function):
@@ -947,9 +949,18 @@ class FunctionSolc(Function):
         for node in self.nodes:
             for ir in node.irs_ssa:
                 if node == self.entry_point:
+                    if isinstance(ir.lvalue, StateIRVariable):
                         additional = [initial_state_variables_instances[ir.lvalue.canonical_name]]
                         additional += last_state_variables_instances[ir.lvalue.canonical_name]
                         ir.rvalues = list(set(additional + ir.rvalues))
+                    # function parameter
+                    else:
+                        # find index of the parameter
+                        idx = self.parameters.index(ir.lvalue.non_ssa_version)
+                        # find non ssa version of that index
+                        additional = [n.ir.arguments[idx] for n in self.reachable_from_nodes]
+                        additional = [a for a in additional if not isinstance(a, Constant)]
+                        ir.rvalues = list(set(additional + ir.rvalues))
                 if isinstance(ir, PhiCallback):
                     callee_ir = ir.callee_ir
                     if isinstance(callee_ir, InternalCall):