[llvm] [llvm] Optimize usub.sat fix for #79690 (PR #151044)

[Yingwei Zheng via llvm-commits]

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@@ -2009,6 +2086,9 @@ Instruction *InstCombinerImpl::foldSelectInstWithICmp(SelectInst &SI,
   if (Instruction *NewSel =
           tryToReuseConstantFromSelectInComparison(SI, *ICI, *this))
     return NewSel;
+  if (Instruction *Folded =
+          foldICmpUSubSatWithAndForMostSignificantBitCmp(SI, ICI, Builder))
+    return replaceInstUsesWith(SI, Folded);
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dtcxzyw wrote:

```suggestion
    return Folded;
```

https://github.com/llvm/llvm-project/pull/151044