[llvm] [InstCombine] simplify `(X * C0) / (X * C1)` into `C0 / C1`. (PR #73204)

[Yingwei Zheng via llvm-commits]

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@@ -1207,6 +1207,18 @@ Instruction *InstCombinerImpl::commonIDivTransforms(BinaryOperator &I) {
     }
   }
 
+  // (X * C0) / (X * C1) --> C0 / C1
+  Constant *C0, *C1;
+  if (match(Op0, m_c_Mul(m_Value(X), m_Constant(C0))) &&
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dtcxzyw wrote:

I think we can generalize this pattern to handle `sdiv (X *nsw Y), (X *nsw Z) -> sdiv Y, Z` iff `sdiv Y, Z` doesn't overflow.
Alive2: https://alive2.llvm.org/ce/z/5TdmfG

https://github.com/llvm/llvm-project/pull/73204