[llvm] SCEV: return std::nullopt for invalid TC (NFC) (PR #94162)

[Nikita Popov via llvm-commits]

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@@ -568,9 +568,10 @@ CacheCost::CacheCost(const LoopVectorTy &Loops, const LoopInfo &LI,
   assert(!Loops.empty() && "Expecting a non-empty loop vector.");
 
   for (const Loop *L : Loops) {
-    unsigned TripCount = SE.getSmallConstantTripCount(L);
-    TripCount = (TripCount == 0) ? DefaultTripCount : TripCount;
-    TripCounts.push_back({L, TripCount});
+    std::optional<unsigned> TripCount = SE.getSmallConstantTripCount(L);
+    if (!TripCount)
+      TripCount = DefaultTripCount;
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nikic wrote:

```suggestion
    unsigned TripCount = SE.getSmallConstantTripCount(L).value_or(DefaultTripCount);
```

https://github.com/llvm/llvm-project/pull/94162