[PATCH] D89773: [IRCE] consolidate profitability check

[Serguei Katkov via Phabricator via llvm-commits]

skatkov created this revision.
skatkov added reviewers: ebrevnov, mkazantsev.
Herald added subscribers: dantrushin, hiraditya.
Herald added a project: LLVM.
skatkov requested review of this revision.

Use BFI if it is available and BPI otherwise.
This promised follow-up after D89451 <https://reviews.llvm.org/D89451>.


https://reviews.llvm.org/D89773

Files:
  llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp


Index: llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
+++ llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
@@ -243,6 +243,10 @@
       llvm::Optional<llvm::function_ref<llvm::BlockFrequencyInfo &()> >;
   GetBFIFunc GetBFI;
 
+  // Returns true if it is profitable to do a transform basing on estimation of
+  // number of iterations.
+  bool checkProfitability(const Loop &L, unsigned LatchBrExitIdx);
+
 public:
   InductiveRangeCheckElimination(ScalarEvolution &SE,
                                  BranchProbabilityInfo *BPI, DominatorTree &DT,
@@ -787,16 +791,6 @@
 
   unsigned LatchBrExitIdx = LatchBr->getSuccessor(0) == Header ? 1 : 0;
 
-  BranchProbability ExitProbability =
-      BPI ? BPI->getEdgeProbability(LatchBr->getParent(), LatchBrExitIdx)
-          : BranchProbability::getZero();
-
-  if (!SkipProfitabilityChecks &&
-      ExitProbability > BranchProbability(1, MaxExitProbReciprocal)) {
-    FailureReason = "short running loop, not profitable";
-    return None;
-  }
-
   ICmpInst *ICI = dyn_cast<ICmpInst>(LatchBr->getCondition());
   if (!ICI || !isa<IntegerType>(ICI->getOperand(0)->getType())) {
     FailureReason = "latch terminator branch not conditional on integral icmp";
@@ -1855,6 +1849,37 @@
   return Changed;
 }
 
+bool
+InductiveRangeCheckElimination::checkProfitability(const Loop &L,
+                                                   unsigned LatchBrExitIdx) {
+  if (SkipProfitabilityChecks)
+    return true;
+  if (GetBFI.hasValue()) {
+    BlockFrequencyInfo &BFI = (*GetBFI)();
+    uint64_t hFreq = BFI.getBlockFreq(L.getHeader()).getFrequency();
+    uint64_t phFreq = BFI.getBlockFreq(L.getLoopPreheader()).getFrequency();
+    if (phFreq != 0 && hFreq != 0 && (hFreq / phFreq < MinRuntimeIterations)) {
+      LLVM_DEBUG(dbgs() << "irce: could not prove profitability: "
+                        << "the estimated number of iterations basing on "
+                           "frequency info is " << (hFreq / phFreq) << "\n";);
+      return false;
+    }
+    return true;
+  }
+
+  if (!BPI)
+    return true;
+  BranchProbability ExitProbability =
+      BPI->getEdgeProbability(L.getLoopLatch(), LatchBrExitIdx);
+  if (ExitProbability > BranchProbability(1, MaxExitProbReciprocal)) {
+    LLVM_DEBUG(dbgs() << "irce: could not prove profitability: "
+                      << "the exit probability is too big " << ExitProbability
+                      << "\n";);
+    return false;
+  }
+  return true;
+}
+
 bool InductiveRangeCheckElimination::run(
     Loop *L, function_ref<void(Loop *, bool)> LPMAddNewLoop) {
   if (L->getBlocks().size() >= LoopSizeCutoff) {
@@ -1901,18 +1926,8 @@
     return false;
   }
   LoopStructure LS = MaybeLoopStructure.getValue();
-  // Profitability check.
-  if (!SkipProfitabilityChecks && GetBFI.hasValue()) {
-    BlockFrequencyInfo &BFI = (*GetBFI)();
-    uint64_t hFreq = BFI.getBlockFreq(LS.Header).getFrequency();
-    uint64_t phFreq = BFI.getBlockFreq(Preheader).getFrequency();
-    if (phFreq != 0 && hFreq != 0 && (hFreq / phFreq < MinRuntimeIterations)) {
-      LLVM_DEBUG(dbgs() << "irce: could not prove profitability: "
-                        << "the estimated number of iterations basing on "
-                           "frequency info is " << (hFreq / phFreq) << "\n";);
-      return false;
-    }
-  }
+  if (!checkProfitability(*L, LS.LatchBrExitIdx))
+    return false;
   const SCEVAddRecExpr *IndVar =
       cast<SCEVAddRecExpr>(SE.getMinusSCEV(SE.getSCEV(LS.IndVarBase), SE.getSCEV(LS.IndVarStep)));
 


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