[llvm] [InstCombine] Simplification for (-a * b) / (a * b) and (a - b) / (b - a). (PR #71768)

[Yingwei Zheng via llvm-commits]

================
@@ -1544,6 +1544,20 @@ Instruction *InstCombinerImpl::visitSDiv(BinaryOperator &I) {
     }
   }
 
+  // -(X * Y) / (X * Y) --> -1
+  if ((match(Op0, m_Neg(m_c_Mul(m_Value(X), m_Value(Y)))) &&
+       match(Op1, m_c_Mul(m_Specific(X), m_Specific(Y)))) ||
+      (match(Op0, m_c_Mul(m_Value(X), m_Value(Y))) &&
+       match(Op1, m_Neg(m_c_Mul(m_Specific(X), m_Specific(Y)))))) {
+    return BinaryOperator::CreateNeg(ConstantInt::get(Ty, 1));
+  };
+
+  // (Y - X) / (X - Y) --> -1
+  if (match(Op0, m_Sub(m_Value(Y), m_Value(X))) &&
+      match(Op1, m_Sub(m_Specific(X), m_Specific(Y)))) {
----------------
dtcxzyw wrote:

```suggestion
  if (match(Op0, m_NSWSub(m_Value(Y), m_Value(X))) &&
      match(Op1, m_NSWSub(m_Specific(X), m_Specific(Y)))) {
```

https://github.com/llvm/llvm-project/pull/71768