[llvm] [LoopInterchange] Fix overflow in cost calculation (PR #111807)

[Sjoerd Meijer via llvm-commits]

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@@ -712,7 +717,12 @@ CacheCost::computeLoopCacheCost(const Loop &L,
   CacheCostTy LoopCost = 0;
   for (const ReferenceGroupTy &RG : RefGroups) {
     CacheCostTy RefGroupCost = computeRefGroupCacheCost(RG, L);
-    LoopCost += RefGroupCost * TripCountsProduct;
+
+    // Saturate the cost to INT MAX if the value can overflow.
+    if (RefGroupCost > (std::numeric_limits<int64_t>::max() / TripCountsProduct))
+      LoopCost = std::numeric_limits<int64_t>::max();
+    else
+      LoopCost += RefGroupCost * TripCountsProduct;
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sjoerdmeijer wrote:

It didn't improve readability, in my opinion, so have left it like this.



https://github.com/llvm/llvm-project/pull/111807