llvm-cov: Very basic top level help

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220926 91177308-0d34-0410-b5e6-96231b3b80d8

tools/llvm-cov/llvm-cov.cpp

@@ -12,6 +12,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/StringSwitch.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Support/Path.h"
 #include <string>
@@ -30,24 +31,29 @@ int convert_for_testing_main(int argc, const char **argv);
 /// \brief The main entry point for the gcov compatible coverage tool.
 int gcov_main(int argc, const char **argv);
 
+/// \brief Top level help.
+int help_main(int argc, const char **argv) {
+  errs() << "OVERVIEW: LLVM code coverage tool\n\n"
+         << "USAGE: llvm-cov {gcov|report|show}\n";
+  return 0;
+}
+
 int main(int argc, const char **argv) {
   // If argv[0] is or ends with 'gcov', always be gcov compatible
   if (sys::path::stem(argv[0]).endswith_lower("gcov"))
     return gcov_main(argc, argv);
 
   // Check if we are invoking a specific tool command.
   if (argc > 1) {
-    int (*func)(int, const char **) = nullptr;
-
-    StringRef command = argv[1];
-    if (command.equals_lower("show"))
-      func = show_main;
-    else if (command.equals_lower("report"))
-      func = report_main;
-    else if (command.equals_lower("convert-for-testing"))
-      func = convert_for_testing_main;
-    else if (command.equals_lower("gcov"))
-      func = gcov_main;
+    typedef int (*MainFunction)(int, const char **);
+    MainFunction func =
+        StringSwitch<MainFunction>(argv[1])
+            .Case("convert-for-testing", convert_for_testing_main)
+            .Case("gcov", gcov_main)
+            .Case("report", report_main)
+            .Case("show", show_main)
+            .Cases("-h", "-help", "--help", help_main)
+            .Default(nullptr);
 
     if (func) {
       std::string Invocation = std::string(argv[0]) + " " + argv[1];