[Analysis] Introduce isSoleCallToLocalFunction (NFC)

[kazu]

Summary

We check to see if a given CallBase is a sole call to a local function
at multiple places in InlineCost.cpp. This patch factors out the
common code.

[taolq]

LGTM

[mtrofin]

llvm/lib/Analysis/InlineCost.cpp

1068

Isn't the Callee obtainable from CB?

[kazu]

llvm/lib/Analysis/InlineCost.cpp

1068

Yes, Callee is obtainable from CB on direct calls. On indirect calls, the callers of this function may specify Callee that is not obtainable CB.

llvm/lib/Analysis/InlineCost.cpp

public:
   virtual ~InlineCostCallAnalyzer() = default;
   int getThreshold() const { return Threshold; }
   int getCost() const { return Cost; }
   Optional<CostBenefitPair> getCostBenefitPair() { return CostBenefit; }
   bool wasDecidedByCostBenefit() const { return DecidedByCostBenefit; }
   bool wasDecidedByCostThreshold() const { return DecidedByCostThreshold; }
 };
 
+// Return true if CB is the sole call to local function Callee.
+static bool isSoleCallToLocalFunction(const CallBase &CB,
+                                      const Function &Callee) {
+  return Callee.hasLocalLinkage() && Callee.hasOneLiveUse() &&
+         &Callee == CB.getCalledFunction();
+}
+
 class InlineCostFeaturesAnalyzer final : public CallAnalyzer {
 private:
   InlineCostFeatures Cost = {};
 
   // FIXME: These constants are taken from the heuristic-based cost visitor.
   // These should be removed entirely in a later revision to avoid reliance on
   // heuristics in the ML inliner.
   static constexpr int JTCostMultiplier = 4;
private:
   InlineResult onAnalysisStart() override {
     increment(InlineCostFeatureIndex::CallSiteCost,
               -1 * getCallsiteCost(this->CandidateCall, DL));
 
     set(InlineCostFeatureIndex::ColdCcPenalty,
         (F.getCallingConv() == CallingConv::Cold));
 
     set(InlineCostFeatureIndex::LastCallToStaticBonus,
-        (F.hasLocalLinkage() && F.hasOneLiveUse() &&
-         &F == CandidateCall.getCalledFunction()));
+        isSoleCallToLocalFunction(CandidateCall, F));
 
     // FIXME: we shouldn't repeat this logic in both the Features and Cost
     // analyzer - instead, we should abstract it to a common method in the
     // CallAnalyzer
     int SingleBBBonusPercent = 50;
     int VectorBonusPercent = TTI.getInlinerVectorBonusPercent();
     Threshold += TTI.adjustInliningThreshold(&CandidateCall);
     Threshold *= TTI.getInliningThresholdMultiplier();
void InlineCostCallAnalyzer::updateThreshold(CallBase &Call, Function &Callee) {
 
   // Finally, take the target-specific inlining threshold multiplier into
   // account.
   Threshold *= TTI.getInliningThresholdMultiplier();
 
   SingleBBBonus = Threshold * SingleBBBonusPercent / 100;
   VectorBonus = Threshold * VectorBonusPercent / 100;
 
-  bool OnlyOneCallAndLocalLinkage = F.hasLocalLinkage() && F.hasOneLiveUse() &&
-                                    &F == Call.getCalledFunction();
   // If there is only one call of the function, and it has internal linkage,
   // the cost of inlining it drops dramatically. It may seem odd to update
   // Cost in updateThreshold, but the bonus depends on the logic in this method.
-  if (OnlyOneCallAndLocalLinkage)
+  if (isSoleCallToLocalFunction(Call, F))
     Cost -= LastCallToStaticBonus;
 }
 
 bool CallAnalyzer::visitCmpInst(CmpInst &I) {
   Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
   // First try to handle simplified comparisons.
   if (simplifyInstruction(I))
     return true;
for (unsigned Idx = 0; Idx != BBWorklist.size(); ++Idx) {
     // them.
     for (unsigned TIdx = 0, TSize = TI->getNumSuccessors(); TIdx != TSize;
          ++TIdx)
       BBWorklist.insert(TI->getSuccessor(TIdx));
 
     onBlockAnalyzed(BB);
   }
 
-  bool OnlyOneCallAndLocalLinkage = F.hasLocalLinkage() && F.hasOneLiveUse() &&
-                                    &F == CandidateCall.getCalledFunction();
   // If this is a noduplicate call, we can still inline as long as
   // inlining this would cause the removal of the caller (so the instruction
   // is not actually duplicated, just moved).
-  if (!OnlyOneCallAndLocalLinkage && ContainsNoDuplicateCall)
+  if (!isSoleCallToLocalFunction(CandidateCall, F) && ContainsNoDuplicateCall)
     return InlineResult::failure("noduplicate");
 
   // If the callee's stack size exceeds the user-specified threshold,
   // do not let it be inlined.
   // The command line option overrides a limit set in the function attributes.
   size_t FinalStackSizeThreshold = StackSizeThreshold;
   if (!StackSizeThreshold.getNumOccurrences())
     if (Optional<int> AttrMaxStackSize = getStringFnAttrAsInt(