[llvm] [InstCombine] Simplify `(add/sub (sub/add) (sub/add))` irrelivant of use-count (PR #105866)

[Yingwei Zheng via llvm-commits]

================
@@ -2286,6 +2289,33 @@ Instruction *InstCombinerImpl::visitSub(BinaryOperator &I) {
     }
   }
 
+  {
+    Value *W, *Z;
+    if (match(Op0, m_AddLike(m_Value(W), m_Value(X))) &&
+        match(Op1, m_AddLike(m_Value(Y), m_Value(Z)))) {
+      Instruction *R = nullptr;
+      if (W == Y)
+        R = BinaryOperator::CreateSub(X, Z);
+      if (W == Z)
----------------
dtcxzyw wrote:

```suggestion
      else if (W == Z)
```
We will create unused sub when W == Y && W == Z.


https://github.com/llvm/llvm-project/pull/105866