[NewPM][Pipeline] Add PipelineTuningOption to set inliner threshold

[aeubanks]

Summary

The legacy PM allowed you to set a custom inliner threshold via

builder.Inliner = llvm::createFunctionInliningPass(inline_threshold);

This allows the same thing to be done with the new PM optimization pipelines.

[asbirlea]

LGTM.

llvm/include/llvm/Passes/PassBuilder.h

public:
   /// Tuning option to enable/disable call graph profile. Its default value is
   /// that of the flag: `-enable-npm-call-graph-profile`.
   bool CallGraphProfile;
 
   /// Tuning option to enable/disable function merging. Its default value is
   /// false.
   bool MergeFunctions;
 
+  /// Tuning option to override the default inliner threshold.
+  int InlinerThreshold;
+
   // Experimental option to eagerly invalidate more analyses. This has the
   // potential to decrease max memory usage in exchange for more compile time.
   // This may affect codegen due to either passes using analyses only when
   // cached, or invalidating and recalculating an analysis that was
   // stale/imprecise but still valid. Currently this invalidates all function
   // analyses after various module->function or cgscc->function adaptors in the
   // default pipelines.
   bool EagerlyInvalidateAnalyses;

llvm/lib/Passes/PassBuilderPipelines.cpp

PipelineTuningOptions::PipelineTuningOptions() {
   LoopVectorization = true;
   SLPVectorization = false;
   LoopUnrolling = true;
   ForgetAllSCEVInLoopUnroll = ForgetSCEVInLoopUnroll;
   LicmMssaOptCap = SetLicmMssaOptCap;
   LicmMssaNoAccForPromotionCap = SetLicmMssaNoAccForPromotionCap;
   CallGraphProfile = true;
   MergeFunctions = EnableMergeFunctions;
+  InlinerThreshold = -1;
   EagerlyInvalidateAnalyses = EnableEagerlyInvalidateAnalyses;
 }
 
 namespace llvm {
 extern cl::opt<unsigned> MaxDevirtIterations;
 extern cl::opt<bool> EnableConstraintElimination;
 extern cl::opt<bool> EnableFunctionSpecialization;
 extern cl::opt<bool> EnableGVNHoist;

 
 static InlineParams getInlineParamsFromOptLevel(OptimizationLevel Level) {
   return getInlineParams(Level.getSpeedupLevel(), Level.getSizeLevel());
 }
 
 ModuleInlinerWrapperPass
 PassBuilder::buildInlinerPipeline(OptimizationLevel Level,
                                   ThinOrFullLTOPhase Phase) {
-  InlineParams IP = getInlineParamsFromOptLevel(Level);
+  InlineParams IP;
+  if (PTO.InlinerThreshold == -1)
+    IP = getInlineParamsFromOptLevel(Level);
+  else
+    IP = getInlineParams(PTO.InlinerThreshold);
   // For PreLinkThinLTO + SamplePGO, set hot-caller threshold to 0 to
   // disable hot callsite inline (as much as possible [1]) because it makes
   // profile annotation in the backend inaccurate.
   //
   // [1] Note the cost of a function could be below zero due to erased
   // prologue / epilogue.
   if (Phase == ThinOrFullLTOPhase::ThinLTOPreLink && PGOOpt &&
       PGOOpt->Action == PGOOptions::SampleUse)