[libcxx-commits] [libcxx] [libc++] std::byteswap support for _BitInt(N) (PR #196512)

[Xavier Roche via libcxx-commits]

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@@ -25,25 +25,37 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 template <integral _Tp>
 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Tp byteswap(_Tp __val) noexcept {
   if constexpr (sizeof(_Tp) == 1) {
+    // Identity for size-1 types. Handled before the __builtin_bswapg path
+    // because some Clang 22 builds have a constexpr-eval bug on the 1-bit
+    // (bool) case (fixed in commit f5410565137c, post-22.1.0).
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xroche wrote:

AFAICS f5410565137c ; not backported yet in 22.x. 

I any case __builtin_bswapg rejects _BitInt(7), _BitInt(13), etc. so size-1 dispatch is needed, but I need to rewrite the condition better.


https://github.com/llvm/llvm-project/pull/196512