diff --git a/cpp/ql/src/semmle/code/cpp/ir/dataflow/internal/DataFlowPrivate.qll b/cpp/ql/src/semmle/code/cpp/ir/dataflow/internal/DataFlowPrivate.qll
index cd52f68c58b8..2f399a24e2d9 100644
--- a/cpp/ql/src/semmle/code/cpp/ir/dataflow/internal/DataFlowPrivate.qll
+++ b/cpp/ql/src/semmle/code/cpp/ir/dataflow/internal/DataFlowPrivate.qll
@@ -28,11 +28,7 @@ private class PrimaryArgumentNode extends ArgumentNode {
 
   PrimaryArgumentNode() { exists(CallInstruction call | op = call.getAnArgumentOperand()) }
 
-  override predicate argumentOf(DataFlowCall call, int pos) {
-    op = call.getPositionalArgumentOperand(pos)
-    or
-    op = call.getThisArgumentOperand() and pos = -1
-  }
+  override predicate argumentOf(DataFlowCall call, int pos) { op = call.getArgumentOperand(pos) }
 
   override string toString() {
     result = "Argument " + op.(PositionalArgumentOperand).getIndex()
@@ -110,10 +106,10 @@ class ReturnIndirectionNode extends ReturnNode {
   override ReturnIndirectionInstruction primary;
 
   override ReturnKind getKind() {
-    result = TIndirectReturnKind(-1) and
-    primary.isThisIndirection()
-    or
-    result = TIndirectReturnKind(primary.getParameter().getIndex())
+    exists(int index |
+      primary.hasIndex(index) and
+      result = TIndirectReturnKind(index)
+    )
   }
 }
 
@@ -500,13 +496,6 @@ class DataFlowType = IRType;
 
 /** A function call relevant for data flow. */
 class DataFlowCall extends CallInstruction {
-  /**
-   * Gets the nth argument for this call.
-   *
-   * The range of `n` is from `0` to `getNumberOfArguments() - 1`.
-   */
-  Node getArgument(int n) { result.asInstruction() = this.getPositionalArgument(n) }
-
   Function getEnclosingCallable() { result = this.getEnclosingFunction() }
 }
 
diff --git a/cpp/ql/src/semmle/code/cpp/ir/dataflow/internal/DataFlowUtil.qll b/cpp/ql/src/semmle/code/cpp/ir/dataflow/internal/DataFlowUtil.qll
index 445152552bd9..2fba66838e9c 100644
--- a/cpp/ql/src/semmle/code/cpp/ir/dataflow/internal/DataFlowUtil.qll
+++ b/cpp/ql/src/semmle/code/cpp/ir/dataflow/internal/DataFlowUtil.qll
@@ -266,10 +266,8 @@ class ParameterIndirectionNode extends ParameterNode {
 
   override predicate isParameterOf(Function f, int pos) {
     exists(int index |
-      f.getParameter(index) = instr.getParameter()
-      or
-      index = -1 and
-      instr.getIRVariable().(IRThisVariable).getEnclosingFunction() = f
+      instr.getEnclosingFunction() = f and
+      instr.hasIndex(index)
     |
       pos = getArgumentPosOfSideEffect(index)
     )
@@ -476,16 +474,8 @@ class DefinitionByReferenceNode extends InstructionNode {
       instr
           .getPrimaryInstruction()
           .(CallInstruction)
-          .getPositionalArgument(instr.getIndex())
+          .getArgument(instr.getIndex())
           .getUnconvertedResultExpression()
-    or
-    result =
-      instr
-          .getPrimaryInstruction()
-          .(CallInstruction)
-          .getThisArgument()
-          .getUnconvertedResultExpression() and
-    instr.getIndex() = -1
   }
 
   /** Gets the parameter through which this value is assigned. */
diff --git a/cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/Instruction.qll b/cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/Instruction.qll
index dd5669413696..c6635264b647 100644
--- a/cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/Instruction.qll
+++ b/cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/Instruction.qll
@@ -588,6 +588,17 @@ class InitializeParameterInstruction extends VariableInstruction {
    * Gets the parameter initialized by this instruction.
    */
   final Language::Parameter getParameter() { result = var.(IRUserVariable).getVariable() }
+
+  /**
+   * Holds if this instruction initializes the parameter with index `index`, or
+   * if `index` is `-1` and this instruction initializes `this`.
+   */
+  pragma[noinline]
+  final predicate hasIndex(int index) {
+    index >= 0 and index = this.getParameter().getIndex()
+    or
+    index = -1 and this.getIRVariable() instanceof IRThisVariable
+  }
 }
 
 /**
@@ -601,6 +612,18 @@ class InitializeIndirectionInstruction extends VariableInstruction {
    * Gets the parameter initialized by this instruction.
    */
   final Language::Parameter getParameter() { result = var.(IRUserVariable).getVariable() }
+
+  /**
+   * Holds if this instruction initializes the memory pointed to by the parameter with
+   * index `index`, or if `index` is `-1` and this instruction initializes the memory
+   * pointed to by `this`.
+   */
+  pragma[noinline]
+  final predicate hasIndex(int index) {
+    index >= 0 and index = this.getParameter().getIndex()
+    or
+    index = -1 and this.getIRVariable() instanceof IRThisVariable
+  }
 }
 
 /**
@@ -775,6 +798,17 @@ class ReturnIndirectionInstruction extends VariableInstruction {
    * Holds if this instruction is the return indirection for `this`.
    */
   final predicate isThisIndirection() { var instanceof IRThisVariable }
+
+  /**
+   * Holds if this instruction is the return indirection for the parameter with index `index`, or
+   * if this instruction is the return indirection for `this` and `index` is `-1`.
+   */
+  pragma[noinline]
+  final predicate hasIndex(int index) {
+    index >= 0 and index = this.getParameter().getIndex()
+    or
+    index = -1 and this.isThisIndirection()
+  }
 }
 
 /**
@@ -1587,6 +1621,22 @@ class CallInstruction extends Instruction {
     result = getPositionalArgumentOperand(index).getDef()
   }
 
+  /**
+   * Gets the argument operand at the specified index, or `this` if `index` is `-1`.
+   */
+  pragma[noinline]
+  final ArgumentOperand getArgumentOperand(int index) {
+    index >= 0 and result = getPositionalArgumentOperand(index)
+    or
+    index = -1 and result = getThisArgumentOperand()
+  }
+
+  /**
+   * Gets the argument at the specified index, or `this` if `index` is `-1`.
+   */
+  pragma[noinline]
+  final Instruction getArgument(int index) { result = getArgumentOperand(index).getDef() }
+
   /**
    * Gets the number of arguments of the call, including the `this` pointer, if any.
    */
diff --git a/cpp/ql/src/semmle/code/cpp/ir/implementation/raw/Instruction.qll b/cpp/ql/src/semmle/code/cpp/ir/implementation/raw/Instruction.qll
index dd5669413696..c6635264b647 100644
--- a/cpp/ql/src/semmle/code/cpp/ir/implementation/raw/Instruction.qll
+++ b/cpp/ql/src/semmle/code/cpp/ir/implementation/raw/Instruction.qll
@@ -588,6 +588,17 @@ class InitializeParameterInstruction extends VariableInstruction {
    * Gets the parameter initialized by this instruction.
    */
   final Language::Parameter getParameter() { result = var.(IRUserVariable).getVariable() }
+
+  /**
+   * Holds if this instruction initializes the parameter with index `index`, or
+   * if `index` is `-1` and this instruction initializes `this`.
+   */
+  pragma[noinline]
+  final predicate hasIndex(int index) {
+    index >= 0 and index = this.getParameter().getIndex()
+    or
+    index = -1 and this.getIRVariable() instanceof IRThisVariable
+  }
 }
 
 /**
@@ -601,6 +612,18 @@ class InitializeIndirectionInstruction extends VariableInstruction {
    * Gets the parameter initialized by this instruction.
    */
   final Language::Parameter getParameter() { result = var.(IRUserVariable).getVariable() }
+
+  /**
+   * Holds if this instruction initializes the memory pointed to by the parameter with
+   * index `index`, or if `index` is `-1` and this instruction initializes the memory
+   * pointed to by `this`.
+   */
+  pragma[noinline]
+  final predicate hasIndex(int index) {
+    index >= 0 and index = this.getParameter().getIndex()
+    or
+    index = -1 and this.getIRVariable() instanceof IRThisVariable
+  }
 }
 
 /**
@@ -775,6 +798,17 @@ class ReturnIndirectionInstruction extends VariableInstruction {
    * Holds if this instruction is the return indirection for `this`.
    */
   final predicate isThisIndirection() { var instanceof IRThisVariable }
+
+  /**
+   * Holds if this instruction is the return indirection for the parameter with index `index`, or
+   * if this instruction is the return indirection for `this` and `index` is `-1`.
+   */
+  pragma[noinline]
+  final predicate hasIndex(int index) {
+    index >= 0 and index = this.getParameter().getIndex()
+    or
+    index = -1 and this.isThisIndirection()
+  }
 }
 
 /**
@@ -1587,6 +1621,22 @@ class CallInstruction extends Instruction {
     result = getPositionalArgumentOperand(index).getDef()
   }
 
+  /**
+   * Gets the argument operand at the specified index, or `this` if `index` is `-1`.
+   */
+  pragma[noinline]
+  final ArgumentOperand getArgumentOperand(int index) {
+    index >= 0 and result = getPositionalArgumentOperand(index)
+    or
+    index = -1 and result = getThisArgumentOperand()
+  }
+
+  /**
+   * Gets the argument at the specified index, or `this` if `index` is `-1`.
+   */
+  pragma[noinline]
+  final Instruction getArgument(int index) { result = getArgumentOperand(index).getDef() }
+
   /**
    * Gets the number of arguments of the call, including the `this` pointer, if any.
    */
diff --git a/cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/Instruction.qll b/cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/Instruction.qll
index dd5669413696..c6635264b647 100644
--- a/cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/Instruction.qll
+++ b/cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/Instruction.qll
@@ -588,6 +588,17 @@ class InitializeParameterInstruction extends VariableInstruction {
    * Gets the parameter initialized by this instruction.
    */
   final Language::Parameter getParameter() { result = var.(IRUserVariable).getVariable() }
+
+  /**
+   * Holds if this instruction initializes the parameter with index `index`, or
+   * if `index` is `-1` and this instruction initializes `this`.
+   */
+  pragma[noinline]
+  final predicate hasIndex(int index) {
+    index >= 0 and index = this.getParameter().getIndex()
+    or
+    index = -1 and this.getIRVariable() instanceof IRThisVariable
+  }
 }
 
 /**
@@ -601,6 +612,18 @@ class InitializeIndirectionInstruction extends VariableInstruction {
    * Gets the parameter initialized by this instruction.
    */
   final Language::Parameter getParameter() { result = var.(IRUserVariable).getVariable() }
+
+  /**
+   * Holds if this instruction initializes the memory pointed to by the parameter with
+   * index `index`, or if `index` is `-1` and this instruction initializes the memory
+   * pointed to by `this`.
+   */
+  pragma[noinline]
+  final predicate hasIndex(int index) {
+    index >= 0 and index = this.getParameter().getIndex()
+    or
+    index = -1 and this.getIRVariable() instanceof IRThisVariable
+  }
 }
 
 /**
@@ -775,6 +798,17 @@ class ReturnIndirectionInstruction extends VariableInstruction {
    * Holds if this instruction is the return indirection for `this`.
    */
   final predicate isThisIndirection() { var instanceof IRThisVariable }
+
+  /**
+   * Holds if this instruction is the return indirection for the parameter with index `index`, or
+   * if this instruction is the return indirection for `this` and `index` is `-1`.
+   */
+  pragma[noinline]
+  final predicate hasIndex(int index) {
+    index >= 0 and index = this.getParameter().getIndex()
+    or
+    index = -1 and this.isThisIndirection()
+  }
 }
 
 /**
@@ -1587,6 +1621,22 @@ class CallInstruction extends Instruction {
     result = getPositionalArgumentOperand(index).getDef()
   }
 
+  /**
+   * Gets the argument operand at the specified index, or `this` if `index` is `-1`.
+   */
+  pragma[noinline]
+  final ArgumentOperand getArgumentOperand(int index) {
+    index >= 0 and result = getPositionalArgumentOperand(index)
+    or
+    index = -1 and result = getThisArgumentOperand()
+  }
+
+  /**
+   * Gets the argument at the specified index, or `this` if `index` is `-1`.
+   */
+  pragma[noinline]
+  final Instruction getArgument(int index) { result = getArgumentOperand(index).getDef() }
+
   /**
    * Gets the number of arguments of the call, including the `this` pointer, if any.
    */
diff --git a/csharp/ql/src/experimental/ir/implementation/raw/Instruction.qll b/csharp/ql/src/experimental/ir/implementation/raw/Instruction.qll
index dd5669413696..c6635264b647 100644
--- a/csharp/ql/src/experimental/ir/implementation/raw/Instruction.qll
+++ b/csharp/ql/src/experimental/ir/implementation/raw/Instruction.qll
@@ -588,6 +588,17 @@ class InitializeParameterInstruction extends VariableInstruction {
    * Gets the parameter initialized by this instruction.
    */
   final Language::Parameter getParameter() { result = var.(IRUserVariable).getVariable() }
+
+  /**
+   * Holds if this instruction initializes the parameter with index `index`, or
+   * if `index` is `-1` and this instruction initializes `this`.
+   */
+  pragma[noinline]
+  final predicate hasIndex(int index) {
+    index >= 0 and index = this.getParameter().getIndex()
+    or
+    index = -1 and this.getIRVariable() instanceof IRThisVariable
+  }
 }
 
 /**
@@ -601,6 +612,18 @@ class InitializeIndirectionInstruction extends VariableInstruction {
    * Gets the parameter initialized by this instruction.
    */
   final Language::Parameter getParameter() { result = var.(IRUserVariable).getVariable() }
+
+  /**
+   * Holds if this instruction initializes the memory pointed to by the parameter with
+   * index `index`, or if `index` is `-1` and this instruction initializes the memory
+   * pointed to by `this`.
+   */
+  pragma[noinline]
+  final predicate hasIndex(int index) {
+    index >= 0 and index = this.getParameter().getIndex()
+    or
+    index = -1 and this.getIRVariable() instanceof IRThisVariable
+  }
 }
 
 /**
@@ -775,6 +798,17 @@ class ReturnIndirectionInstruction extends VariableInstruction {
    * Holds if this instruction is the return indirection for `this`.
    */
   final predicate isThisIndirection() { var instanceof IRThisVariable }
+
+  /**
+   * Holds if this instruction is the return indirection for the parameter with index `index`, or
+   * if this instruction is the return indirection for `this` and `index` is `-1`.
+   */
+  pragma[noinline]
+  final predicate hasIndex(int index) {
+    index >= 0 and index = this.getParameter().getIndex()
+    or
+    index = -1 and this.isThisIndirection()
+  }
 }
 
 /**
@@ -1587,6 +1621,22 @@ class CallInstruction extends Instruction {
     result = getPositionalArgumentOperand(index).getDef()
   }
 
+  /**
+   * Gets the argument operand at the specified index, or `this` if `index` is `-1`.
+   */
+  pragma[noinline]
+  final ArgumentOperand getArgumentOperand(int index) {
+    index >= 0 and result = getPositionalArgumentOperand(index)
+    or
+    index = -1 and result = getThisArgumentOperand()
+  }
+
+  /**
+   * Gets the argument at the specified index, or `this` if `index` is `-1`.
+   */
+  pragma[noinline]
+  final Instruction getArgument(int index) { result = getArgumentOperand(index).getDef() }
+
   /**
    * Gets the number of arguments of the call, including the `this` pointer, if any.
    */
diff --git a/csharp/ql/src/experimental/ir/implementation/unaliased_ssa/Instruction.qll b/csharp/ql/src/experimental/ir/implementation/unaliased_ssa/Instruction.qll
index dd5669413696..c6635264b647 100644
--- a/csharp/ql/src/experimental/ir/implementation/unaliased_ssa/Instruction.qll
+++ b/csharp/ql/src/experimental/ir/implementation/unaliased_ssa/Instruction.qll
@@ -588,6 +588,17 @@ class InitializeParameterInstruction extends VariableInstruction {
    * Gets the parameter initialized by this instruction.
    */
   final Language::Parameter getParameter() { result = var.(IRUserVariable).getVariable() }
+
+  /**
+   * Holds if this instruction initializes the parameter with index `index`, or
+   * if `index` is `-1` and this instruction initializes `this`.
+   */
+  pragma[noinline]
+  final predicate hasIndex(int index) {
+    index >= 0 and index = this.getParameter().getIndex()
+    or
+    index = -1 and this.getIRVariable() instanceof IRThisVariable
+  }
 }
 
 /**
@@ -601,6 +612,18 @@ class InitializeIndirectionInstruction extends VariableInstruction {
    * Gets the parameter initialized by this instruction.
    */
   final Language::Parameter getParameter() { result = var.(IRUserVariable).getVariable() }
+
+  /**
+   * Holds if this instruction initializes the memory pointed to by the parameter with
+   * index `index`, or if `index` is `-1` and this instruction initializes the memory
+   * pointed to by `this`.
+   */
+  pragma[noinline]
+  final predicate hasIndex(int index) {
+    index >= 0 and index = this.getParameter().getIndex()
+    or
+    index = -1 and this.getIRVariable() instanceof IRThisVariable
+  }
 }
 
 /**
@@ -775,6 +798,17 @@ class ReturnIndirectionInstruction extends VariableInstruction {
    * Holds if this instruction is the return indirection for `this`.
    */
   final predicate isThisIndirection() { var instanceof IRThisVariable }
+
+  /**
+   * Holds if this instruction is the return indirection for the parameter with index `index`, or
+   * if this instruction is the return indirection for `this` and `index` is `-1`.
+   */
+  pragma[noinline]
+  final predicate hasIndex(int index) {
+    index >= 0 and index = this.getParameter().getIndex()
+    or
+    index = -1 and this.isThisIndirection()
+  }
 }
 
 /**
@@ -1587,6 +1621,22 @@ class CallInstruction extends Instruction {
     result = getPositionalArgumentOperand(index).getDef()
   }
 
+  /**
+   * Gets the argument operand at the specified index, or `this` if `index` is `-1`.
+   */
+  pragma[noinline]
+  final ArgumentOperand getArgumentOperand(int index) {
+    index >= 0 and result = getPositionalArgumentOperand(index)
+    or
+    index = -1 and result = getThisArgumentOperand()
+  }
+
+  /**
+   * Gets the argument at the specified index, or `this` if `index` is `-1`.
+   */
+  pragma[noinline]
+  final Instruction getArgument(int index) { result = getArgumentOperand(index).getDef() }
+
   /**
    * Gets the number of arguments of the call, including the `this` pointer, if any.
    */