diff --git a/llvm/tools/llvm-extract/llvm-extract.cpp b/llvm/tools/llvm-extract/llvm-extract.cpp
--- a/llvm/tools/llvm-extract/llvm-extract.cpp
+++ b/llvm/tools/llvm-extract/llvm-extract.cpp
@@ -74,8 +74,11 @@
 
 // ExtractBlocks - The blocks to extract from the module.
 static cl::list<std::string> ExtractBlocks(
-    "bb", cl::desc("Specify <function, basic block> pairs to extract"),
-    cl::ZeroOrMore, cl::value_desc("function:bb"), cl::cat(ExtractCat));
+    "bb",
+    cl::desc("Specify <function, basic block[;group]> pairs to extract, "
+             "region must be single entry."),
+    cl::ZeroOrMore, cl::value_desc("function:bb[;bb2...]"),
+    cl::cat(ExtractCat));
 
 // ExtractAlias - The alias to extract from the module.
 static cl::list<std::string>