[llvm] [Reassociate] Preserve NSW flags after expr tree rewriting (PR #93105)

[Akshay Deodhar via llvm-commits]

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@@ -648,6 +651,13 @@ static bool LinearizeExprTree(Instruction *I,
     // Ensure the leaf is only output once.
     It->second = 0;
     Ops.push_back(std::make_pair(V, Weight));
+    if (Opcode == Instruction::Add && Flags.AllKnownNonNegative &&
+        Flags.HasNSW) {
+      // Note: AllKnownNegative can be true in a case where one of the operands
+      // is negative, but one the operators is not NSW. AllKnownNegative should
+      // not be used independently of HasNSW
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akshayrdeodhar wrote:

Makes sense, done.

https://github.com/llvm/llvm-project/pull/93105