================ @@ -3464,6 +3464,54 @@ Query for this feature with ``__has_builtin(__builtin_trap)``. ``__builtin_arm_trap`` is lowered to the ``llvm.aarch64.break`` builtin, and then to ``brk #payload``. +``__builtin_allow_runtime_check`` +--------------------------------- + +``__builtin_allow_runtime_check`` return true if the check at the current +program location should be executed. It is expected to be used to implement +``assert`` like checks which can be safely removed by optimizer. + +**Syntax**: + +.. code-block:: c++ + + bool __builtin_allow_runtime_check(const char* kind) + +**Example of use**: + +.. code-block:: c++ + + if (__builtin_allow_runtime_check("mycheck") && !ExpensiveCheck()) { + abort(); + } + +**Description** + +``__builtin_allow_runtime_check`` is lowered to ` ``llvm.allow.runtime.check`` +<https://llvm.org/docs/LangRef.html#llvm-allow-runtime-check-intrinsic>`_ +builtin. + +The ``__builtin_allow_runtime_check()`` is expected to be used with control +flow conditions such as in ``if`` to guard expensive runtime checks. The +specific rules for selecting permitted checks can differ and are controlled by +the compiler options. + +Flags to control checks: +* ``-mllvm -lower-allow-check-percentile-cutoff-hot=N`` where N is PGO hotness +cutoff in range ``[0, 999999]`` to disallow checks in hot code. +* ``-mllvm -lower-allow-check-random-rate=P`` where P is number in range +``[0.0, 1.0]`` representation probability of keeping a check. +* If both flags are specified, ``-lower-allow-check-random-rate`` takes +precedence. +* If none is specified, ``__builtin_allow_runtime_check`` is lowered as +``true``, allowing all checks. + +Parameter ``kind`` is a string literal representing a user selected kind for +guarded check. It's unused now. It will enable kind specific lowering in future. ---------------- AaronBallman wrote:
```suggestion guarded check. It's unused now. It will enable kind-specific lowering in future. ``` https://github.com/llvm/llvm-project/pull/87568 _______________________________________________ llvm-branch-commits mailing list llvm-branch-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits