Index: llvm/docs/CodingStandards.rst
===================================================================
--- llvm/docs/CodingStandards.rst
+++ llvm/docs/CodingStandards.rst
@@ -1026,6 +1026,21 @@
 The idea is to reduce indentation and the amount of code you have to keep track
 of when reading the code.
 
+Note: this advice does not apply to a ``constexpr if`` statement. The
+substatement of the ``else`` clause may be a discarded statement, so removing
+the ``else`` can cause unexpected template instantiations. Thus, the following
+example is correct:
+
+.. code-block:: c++
+
+  template <typename Ty>
+  static int foo(Ty T) {
+    if constexpr (std::is_integral_v<Ty>)
+      return 10 + T;
+    else
+      return 100;
+  }
+
 Turn Predicate Loops into Predicate Functions
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^