[llvm] [InstCombine] Fold `(mul (div exact X, C0), C1)` -> `(div exact X, C0/C1)` (PR #96915)

[Yingwei Zheng via llvm-commits]

================
@@ -365,6 +365,28 @@ Instruction *InstCombinerImpl::visitMul(BinaryOperator &I) {
       return BinaryOperator::CreateMul(NegOp0, X);
   }
 
+  if (Op0->hasOneUse()) {
+    // (mul (div exact X, C0), C1)
+    //    -> (div exact C0 / C1)
----------------
dtcxzyw wrote:

```suggestion
    //    -> (div exact X, C0 / C1)
```

https://github.com/llvm/llvm-project/pull/96915