Fix opt --help ordering of available optimizations.

[erichkeane]

Summary

Introduced in -r283004, the PassNameParser sorts Optimization options in reverse. This is because the commit replaced a compare function with "<" (which would seemingly be proper based on the name of the comparison function). The result is the 'true' result is converted to '1', which is inverted.

This patch fixes this by replacing the '<' operator call on StringRef with a call to the StringRef compare function. It also renames the function to better reflect its meaning.

[erichkeane]

include/llvm/IR/LegacyPassNameParser.h

91

Craig pointed out this line needs to be -1 char, I've fixed it in my local WS, and will get it when I commit.

[craig.topper]

LGTM

include/llvm/IR/LegacyPassNameParser.h

void passRegistered(const PassInfo *P) override {
     addLiteralOption(P->getPassArgument().data(), P, P->getPassName().data());
   }
   void passEnumerate(const PassInfo *P) override { passRegistered(P); }
 
   // printOptionInfo - Print out information about this option.  Override the
   // default implementation to sort the table before we print...
   void printOptionInfo(const cl::Option &O, size_t GlobalWidth) const override {
     PassNameParser *PNP = const_cast<PassNameParser*>(this);
-    array_pod_sort(PNP->Values.begin(), PNP->Values.end(), ValLessThan);
+    array_pod_sort(PNP->Values.begin(), PNP->Values.end(), ValCompare);
     cl::parser<const PassInfo*>::printOptionInfo(O, GlobalWidth);
   }
 
 private:
-  // ValLessThan - Provide a sorting comparator for Values elements...
-  static int ValLessThan(const PassNameParser::OptionInfo *VT1,
+  // ValCompare - Provide a sorting comparator for Values elements...
+  static int ValCompare(const PassNameParser::OptionInfo *VT1,
                          const PassNameParser::OptionInfo *VT2) {
-    return VT1->Name < VT2->Name;
+    return VT1->Name.compare(VT2->Name);
   }
 };
 
 ///===----------------------------------------------------------------------===//
 /// FilteredPassNameParser class - Make use of the pass registration
 /// mechanism to automatically add a command line argument to opt for
 /// each pass that satisfies a filter criteria.  Filter should return
 /// true for passes to be registered as command-line options.