[llvm] [InstCombine] Improve handling of `not` and free inversion. (PR #66787)

[Nikita Popov via llvm-commits]

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@@ -1662,6 +1662,24 @@ Instruction *InstCombinerImpl::visitAdd(BinaryOperator &I) {
                                     m_c_UMin(m_Deferred(A), m_Deferred(B))))))
     return BinaryOperator::CreateWithCopiedFlags(Instruction::Add, A, B, &I);
 
+  // (~X) + (~Y) --> (-2 - Y) - X
+  {
+    // To ensure we can save instructions we need to ensure that we either
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nikic wrote:

```suggestion
    // To ensure we can save instructions we need to ensure that we
```

https://github.com/llvm/llvm-project/pull/66787