[llvm-profgen] Error out for unsupported AutoFDO profile generate with probe

[wenlei]

Summary

Error out instead of siliently generate empty profile when trying to generate AutoFDO profile with probe binary.

[wlei]

LGTM, thanks!

[wenlei]

update message.

llvm/tools/llvm-profgen/ProfileGenerator.cpp

if (Ret.second) {
     FProfile.setContext(Context);
   }
   return Ret.first->second;
 }
 
 void ProfileGenerator::generateProfile() {
   if (Binary->usePseudoProbes()) {
     // TODO: Support probe based profile generation
+    exitWithError("Probe based profile generation not supported for AutoFDO.");
   } else {
     generateLineNumBasedProfile();
   }
   postProcessProfiles();
 }
 
 void ProfileGenerator::postProcessProfiles() {
   computeSummaryAndThreshold();