================ @@ -96,6 +101,37 @@ the ``<cmath>`` header file to conditionally make a function constexpr whenever the constant evaluation of the corresponding builtin (for example, ``std::fmax`` calls ``__builtin_fmax``) is supported in Clang. +``__has_target_builtin`` +------------------------ + +This function-like macro takes a single identifier argument that is the name of +a builtin function, a builtin pseudo-function (taking one or more type +arguments), or a builtin template. +It evaluates to 1 if the builtin is supported on the current target or 0 if not. +The behavior is different than ``__has_builtin`` when there is an auxiliary target, +such when offloading to a target device. +It can be used like this: + +.. code-block:: c++ + + #ifndef __has_target_builtin // Optional of course. + #define __has_target_builtin(x) 0 // Compatibility with non-clang compilers. + #endif ---------------- yxsamliu wrote:
if we make it available to C++, we'd better document the following invalid usage which originally leads to this extension: ``` #if !__has_target_builtin(__wfi) static __inline__ void __attribute__((__always_inline__, __nodebug__)) __wfi(void) { __builtin_arm_wfi(); } #endif ``` we should emphasize that a C++ header may be used by offloading languages, and in offloading language, the same source is compiled for host and device target separately. A builtin not available for the current target does not justify defining the builtin for both host and device targets. In this case, better to use `__has_builtin(__wfi)` since it makes sure the condition is true for both hosts and device targets so that the code won't break when used in offloading languages. https://github.com/llvm/llvm-project/pull/126324 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits