C++: Add missing QLDoc.

Author: MathiasVP

cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/DataFlowUtil.qll

@@ -646,6 +646,7 @@ private class RawIndirectOperand extends Node, TRawIndirectOperand {
   /** Gets the underlying instruction. */
   Operand getOperand() { result = operand }
 
+  /** Gets the underlying indirection index. */
   int getIndirectionIndex() { result = indirectionIndex }
 
   override Function getFunction() { result = this.getOperand().getDef().getEnclosingFunction() }
@@ -665,6 +666,15 @@ private class RawIndirectOperand extends Node, TRawIndirectOperand {
   }
 }
 
+/**
+ * INTERNAL: Do not use.
+ *
+ * A node that represents the indirect value of an operand in the IR
+ * after `index` number of loads.
+ *
+ * Note: Unlike `RawIndirectOperand`, a value of type `IndirectOperand` may
+ * be an `OperandNode`.
+ */
 class IndirectOperand extends Node {
   Operand operand;
   int indirectionIndex;
@@ -676,10 +686,16 @@ class IndirectOperand extends Node {
     this.(OperandNode).getOperand() = Ssa::getIRBackedIndirectOperand(operand, indirectionIndex)
   }
 
+  /** Gets the underlying operand. */
   Operand getOperand() { result = operand }
 
+  /** Gets the underlying indirection index. */
   int getIndirectionIndex() { result = indirectionIndex }
 
+  /**
+   * Holds if this `IndirectOperand` is represented directly in the IR instead of
+   * a `RawIndirectionOperand` with operand `op` and indirection index `index`.
+   */
   predicate isIRBackedBy(Operand op, int index) {
     this instanceof OperandNode and
     (
@@ -723,6 +739,7 @@ private class RawIndirectInstruction extends Node, TRawIndirectInstruction {
   /** Gets the underlying instruction. */
   Instruction getInstruction() { result = instr }
 
+  /** Gets the underlying indirection index. */
   int getIndirectionIndex() { result = indirectionIndex }
 
   override Function getFunction() { result = this.getInstruction().getEnclosingFunction() }
@@ -742,6 +759,15 @@ private class RawIndirectInstruction extends Node, TRawIndirectInstruction {
   }
 }
 
+/**
+ * INTERNAL: Do not use.
+ *
+ * A node that represents the indirect value of an instruction in the IR
+ * after `index` number of loads.
+ *
+ * Note: Unlike `RawIndirectInstruction`, a value of type `IndirectInstruction` may
+ * be an `InstructionNode`.
+ */
 class IndirectInstruction extends Node {
   Instruction instr;
   int indirectionIndex;
@@ -754,10 +780,16 @@ class IndirectInstruction extends Node {
       Ssa::getIRBackedIndirectInstruction(instr, indirectionIndex)
   }
 
+  /** Gets the underlying instruction. */
   Instruction getInstruction() { result = instr }
 
+  /** Gets the underlying indirection index. */
   int getIndirectionIndex() { result = indirectionIndex }
 
+  /**
+   * Holds if this `IndirectInstruction` is represented directly in the IR instead of
+   * a `RawIndirectionInstruction` with instruction `i` and indirection index `index`.
+   */
   predicate isIRBackedBy(Instruction i, int index) {
     this instanceof InstructionNode and
     (