C++: Fix join-order in 'isArgumentForParameter'.

Author: MathiasVP

cpp/ql/lib/semmle/code/cpp/ir/implementation/aliased_ssa/internal/AliasAnalysis.qll

@@ -266,6 +266,20 @@ private predicate operandReturned(Operand operand, IntValue bitOffset) {
   bitOffset = Ints::unknown()
 }
 
+pragma[nomagic]
+private predicate initializeParameterInstructionHasVariable(
+  IRVariable var, InitializeParameterInstruction init
+) {
+  init.getIRVariable() = var
+}
+
+private predicate instructionInitializesThisInFunction(
+  Language::Function f, InitializeParameterInstruction init
+) {
+  initializeParameterInstructionHasVariable(any(IRThisVariable var), pragma[only_bind_into](init)) and
+  init.getEnclosingFunction() = f
+}
+
 private predicate isArgumentForParameter(
   CallInstruction ci, Operand operand, InitializeParameterInstruction init
 ) {
@@ -275,8 +289,7 @@ private predicate isArgumentForParameter(
     (
       init.getParameter() = f.getParameter(operand.(PositionalArgumentOperand).getIndex())
       or
-      init.getIRVariable() instanceof IRThisVariable and
-      unique( | | init.getEnclosingFunction()) = f and
+      instructionInitializesThisInFunction(f, init) and
       operand instanceof ThisArgumentOperand
     ) and
     not Language::isFunctionVirtual(f) and