================
@@ -636,9 +636,13 @@ static void updateBranchWeights(Instruction *Term,
WeightInfo &Info) {
MDB.createBranchWeights(Info.Weights));
for (auto [Idx, SubWeight] : enumerate(Info.SubWeights))
if (SubWeight != 0)
- Info.Weights[Idx] = Info.Weights[Idx] > SubWeight
- ? Info.Weights[Idx] - SubWeight
- : 1;
+ // Don't set the probability of taking the edge from latch to loop header
+ // to less than 1, as this could significantly reduce the loop's hotness,
+ // which would be incorrect in the case of underestimating the trip
count.
+ Info.Weights[Idx] =
+ Info.Weights[Idx] > SubWeight
+ ? std::max(Info.Weights[Idx] - SubWeight, SubWeight)
+ : SubWeight;
----------------
MatzeB wrote:
Actually this suggestion may be susceptible to overflow... So please keep your
original `std::max` variant of the code then and ignore this!
https://github.com/llvm/llvm-project/pull/70094
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