[doc] Give a workaround for a FileCheck regex that ends in a brace.
Addresses PR42864.
llvm-svn: 367689
diff --git a/llvm/docs/CommandGuide/FileCheck.rst b/llvm/docs/CommandGuide/FileCheck.rst
index c5521e4..429f3ad 100644
--- a/llvm/docs/CommandGuide/FileCheck.rst
+++ b/llvm/docs/CommandGuide/FileCheck.rst
@@ -527,7 +527,10 @@
visually distinct, and you don't need to use escape characters within the double
braces like you would in C. In the rare case that you want to match double
braces explicitly from the input, you can use something ugly like
-``{{[{][{]}}`` as your pattern.
+``{{[}][}]}}`` as your pattern. Or if you are using the repetition count
+syntax, for example ``[[:xdigit:]]{8}`` to match exactly 8 hex digits, you
+would need to add parentheses like this ``{{([[:xdigit:]]{8})}}`` to avoid
+confusion with FileCheck's closing double-brace.
FileCheck String Substitution Blocks
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~