[PATCH] D99302: [InlineCost] Make cost-benefit decision explicit

[Wenlei He via Phabricator via llvm-commits]

wenlei created this revision.
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With cost-benefit analysis for inlining, we bypass the cost-threshold by returning inline result from call analyzer early.

However the cost and threshold are still available from call analyzer, and when cost is actually higher than threshold, we incorrect set the reason.

The change makes the decision from cost-benefit analysis explicit. It's mostly NFC, except that it allows the priority-based sample loader inliner used by CSSPGO to use cost-benefit heuristic.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D99302

Files:
  llvm/lib/Analysis/InlineCost.cpp


Index: llvm/lib/Analysis/InlineCost.cpp
===================================================================
--- llvm/lib/Analysis/InlineCost.cpp
+++ llvm/lib/Analysis/InlineCost.cpp
@@ -489,6 +489,9 @@
   // sense that it's not weighted by profile counts at all.
   int ColdSize = 0;
 
+  // Whether inlining is decided by cost-benefit analysis.
+  bool DecidedByCostBenefit = false;
+
   bool SingleBB = true;
 
   unsigned SROACostSavings = 0;
@@ -825,6 +828,7 @@
       Threshold -= VectorBonus / 2;
 
     if (auto Result = costBenefitAnalysis()) {
+      DecidedByCostBenefit = true;
       if (Result.getValue())
         return InlineResult::success();
       else
@@ -926,6 +930,7 @@
   virtual ~InlineCostCallAnalyzer() {}
   int getThreshold() { return Threshold; }
   int getCost() { return Cost; }
+  bool wasDecidedByCostBenefit() { return DecidedByCostBenefit; }
 };
 } // namespace
 
@@ -2610,6 +2615,8 @@
   LLVM_DEBUG(CA.dump());
 
   // Check if there was a reason to force inlining or no inlining.
+  if (ShouldInline.isSuccess() && CA.wasDecidedByCostBenefit())
+    return InlineCost::getAlways("benefit over cost");
   if (!ShouldInline.isSuccess() && CA.getCost() < CA.getThreshold())
     return InlineCost::getNever(ShouldInline.getFailureReason());
   if (ShouldInline.isSuccess() && CA.getCost() >= CA.getThreshold())


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