[llvm] [DAGCombiner] Fold subtraction if above a constant threshold to `umin` (PR #135194)

[Piotr Fusik via llvm-commits]

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@@ -12074,6 +12078,17 @@ SDValue DAGCombiner::visitSELECT(SDNode *N) {
 
     if (SDValue NewSel = SimplifySelect(DL, N0, N1, N2))
       return NewSel;
+
+    // (select (ugt x, C), (add x, ~C), x) -> (umin (add x, ~C), x)
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pfusik wrote:

Do you have a reproducer?
If it's `add nuw/nsw`, I think the solution would be to drop `nuw/nsw` during this transform.

https://github.com/llvm/llvm-project/pull/135194