[CommandLineParser] Add DefaultOption flag

Summary: Add DefaultOption flag to CommandLineParser which provides a
default option or alias, but allows users to override it for some
other purpose as needed.

Also, add `-h` as a default alias to `-help`, which can be seamlessly
overridden by applications like llvm-objdump and llvm-readobj which
use `-h` as an alias for other options.

(relanding after revert, r358414)
Added DefaultOptions.clear() to reset().

Reviewers: alexfh, klimek

Reviewed By: klimek

Subscribers: kristina, MaskRay, mehdi_amini, inglorion, dexonsmith, hiraditya, llvm-commits, jhenderson, arphaman, cfe-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D59746

llvm-svn: 358428

1 files changed, 0 insertions, 7 deletions

diff --git a/llvm/tools/llvm-opt-report/OptReport.cpp b/llvm/tools/llvm-opt-report/OptReport.cpp
index 3ea71fc47ef..a6ca6146b48 100644
--- a/llvm/tools/llvm-opt-report/OptReport.cpp
+++ b/llvm/tools/llvm-opt-report/OptReport.cpp
@@ -36,8 +36,6 @@
 using namespace llvm;
 using namespace llvm::yaml;
 
-static cl::opt<bool> Help("h", cl::desc("Alias for -help"), cl::Hidden);
-
 // Mark all our options with this category, everything else (except for -version
 // and -help) will be hidden.
 static cl::OptionCategory
@@ -440,11 +438,6 @@ int main(int argc, const char **argv) {
       "A tool to generate an optimization report from YAML optimization"
       " record files.\n");
 
-  if (Help) {
-    cl::PrintHelpMessage();
-    return 0;
-  }
-
   LocationInfoTy LocationInfo;
   if (!readLocationInfo(LocationInfo))
     return 1;