[llvm] [VPlanValue] Introduce hasOneUser(). nfc (PR #170826)

[Graham Hunter via llvm-commits]

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@@ -150,11 +150,21 @@ class LLVM_ABI_FOR_TEST VPValue {
 
   bool hasOneUse() const { return getNumUsers() == 1; }
 
+  /// Returns true if the value has exactly one unique user, ignoring multiple
+  /// uses by the same user.
+  bool hasOneUser() const {
+    if (getNumUsers() == 0)
+      return false;
+    if (hasOneUse())
+      return true;
+    return std::equal(std::next(user_begin()), user_end(), user_begin());
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huntergr-arm wrote:

nit: Could use `all_equal(Users)`

https://github.com/llvm/llvm-project/pull/170826