Create SampleProfileLoader pass in llvm instead of clang

[danielcdh]

Summary

We used to create SampleProfileLoader pass in clang. This makes LTO/ThinLTO unable to add this pass in the linker plugin. This patch moves the SampleProfileLoader pass creation from clang to llvm pass manager builder.

[dnovillo]

LGTM

[danielcdh]

was reverted due to bot breaking

include/llvm/Transforms/IPO/PassManagerBuilder.h

public:
   bool PerformThinLTO;
 
   /// Enable profile instrumentation pass.
   bool EnablePGOInstrGen;
   /// Profile data file name that the instrumentation will be written to.
   std::string PGOInstrGen;
   /// Path of the profile data file.
   std::string PGOInstrUse;
+  /// Path of the sample Profile data file.
+  std::string PGOSampleUse;
 
 private:
   /// ExtensionList - This is list of all of the extensions that are registered.
   std::vector<std::pair<ExtensionPointTy, ExtensionFn>> Extensions;
 
 public:
   PassManagerBuilder();
   ~PassManagerBuilder();

lib/Transforms/IPO/PassManagerBuilder.cpp

void PassManagerBuilder::addFunctionSimplificationPasses(
   MPM.add(createCFGSimplificationPass()); // Merge & remove BBs
   // Clean up after everything.
   addInstructionCombiningPass(MPM);
   addExtensionsToPM(EP_Peephole, MPM);
 }
 
 void PassManagerBuilder::populateModulePassManager(
     legacy::PassManagerBase &MPM) {
+  if (!PGOSampleUse.empty()) {
+    MPM.add(createPruneEHPass());
+    MPM.add(createSampleProfileLoaderPass(PGOSampleUse));
+  }
+
   // Allow forcing function attributes as a debugging and tuning aid.
   MPM.add(createForceFunctionAttrsLegacyPass());
 
   // If all optimizations are disabled, just run the always-inline pass and,
   // if enabled, the function merging pass.
   if (OptLevel == 0) {
     addPGOInstrPasses(MPM);
     if (Inliner) {