[llvm] [InstCombine] Add optimization to combine adds through zext nneg, and add testcase (PR #157723)

[Yingwei Zheng via llvm-commits]

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@@ -1910,6 +1910,33 @@ Instruction *InstCombinerImpl::visitAdd(BinaryOperator &I) {
   if (Instruction *Res = foldBinOpOfSelectAndCastOfSelectCondition(I))
     return Res;
 
+  {
+    Value *X;
+    const APInt *C1, *C2;
+    if (match(&I, m_c_Add(m_NNegZExt(m_Add(m_Value(X), m_APInt(C1))),
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dtcxzyw wrote:

```suggestion
    if (match(&I, m_Add(m_NNegZExt(m_Add(m_Value(X), m_APInt(C1))),
```

https://github.com/llvm/llvm-project/pull/157723