Index: llvm/docs/TestingGuide.rst
===================================================================
--- llvm/docs/TestingGuide.rst
+++ llvm/docs/TestingGuide.rst
@@ -513,7 +513,10 @@
   expression is satisfied if any feature matches the regular expression. Regular
   expressions can appear inside an identifier, so for example ``he{{l+}}o`` would match
   ``helo``, ``hello``, ``helllo``, and so on.
-- Substrings of the target triple (``UNSUPPORTED`` and ``XFAIL`` only).
+- The default target triple, preceded by the string ``target=`` (for example,
+  ``target=x86_64-pc-windows-msvc``). Typically regular expressions are used
+  to match parts of the triple (for example, ``target={{.*}}-windows{{.*}}``
+  to match any Windows target triple).
 
 | ``REQUIRES`` enables the test if all expressions are true.
 | ``UNSUPPORTED`` disables the test if any expression is true.