[clang] [analyzer] Allow recursive functions to be trivial. (PR #91876)

[Artem Dergachev via cfe-commits]

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@@ -231,6 +231,15 @@ class RefCounted {
   void method();
   void someFunction();
   int otherFunction();
+  unsigned recursiveTrivialFunction(int n) { return !n ? 1 : recursiveTrivialFunction(n - 1);  }
+  unsigned recursiveComplexFunction(int n) { return !n ? otherFunction() : recursiveComplexFunction(n - 1);  }
+  unsigned mutuallyRecursiveFunction1(int n) { return n < 0 ? 1 : (n % 2 ? mutuallyRecursiveFunction2(n - 2) : mutuallyRecursiveFunction1(n - 1)); }
+  unsigned mutuallyRecursiveFunction2(int n) { return n < 0 ? 1 : (n % 3 ? mutuallyRecursiveFunction2(n - 3) : mutuallyRecursiveFunction1(n - 2)); }
+  unsigned mutuallyRecursiveFunction3(int n) { return n < 0 ? 1 : (n % 5 ? mutuallyRecursiveFunction3(n - 5) : mutuallyRecursiveFunction4(n - 3)); }
+  unsigned mutuallyRecursiveFunction4(int n) { return n < 0 ? 1 : (n % 7 ? otherFunction() : mutuallyRecursiveFunction3(n - 3)); }
+  unsigned mutuallyRecursiveFunction5(unsigned n) { return n > 100 ? 2 : (n % 2 ? mutuallyRecursiveFunction5(n + 1) : mutuallyRecursiveFunction6(n + 2)); }
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haoNoQ wrote:

These probably shouldn't be called "mutually" recursive because you never really go back from 6 to 5 or from 7 to 6. Though, I don't have a better name for such contraption.

https://github.com/llvm/llvm-project/pull/91876