Add a better head-of-file comment.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@12447 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/llc/llc.cpp b/tools/llc/llc.cpp
index f09d8ec..b995e7d 100644
--- a/tools/llc/llc.cpp
+++ b/tools/llc/llc.cpp
@@ -7,7 +7,9 @@
 // 
 //===----------------------------------------------------------------------===//
 //
-// This is the llc code generator.
+// This is the llc code generator driver. It provides a convenient
+// command-line interface for generating native assembly-language code 
+// or C code, given LLVM bytecode.
 //
 //===----------------------------------------------------------------------===//