--- gcc/doc/invoke.texi
+++ gcc/doc/invoke.texi
@@ -3516,6 +3516,19 @@ result in a call to @code{terminate}.
Disable the warning about the case when a conversion function converts an
object to the same type, to a base class of that type, or to void; such
a conversion function will never be called.
+
+@item -Wvolatile @r{(C++ and Objective-C++ only)}
+@opindex Wvolatile
+@opindex Wno-volatile
+Warn about deprecated uses of the volatile qualifier. This includes postfix
+and prefix @code{++} and @code{--} expressions of volatile-qualified types,
+using simple assignments where the left operand is a volatile-qualified
+non-class type for their value, compound assignments where the left operand
+is a volatile-qualified non-class type, volatile-qualified function return
+type, volatile-qualified parameter type, and structured bindings of a
+volatile-qualified type. This usage was deprecated in C++20.