<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Richard recently made __builtin_memcpy constexpr in some cases: <a href="https://reviews.llvm.org/rL338941" class="">https://reviews.llvm.org/rL338941</a><br class="">His patch currently disallows all type-puns.<div class=""><br class=""></div><div class="">Erik is looking at implementing a bit_cast intrinsic for clang, at which point libc++ can use it. ADT won’t be able to do so until we migrate to C++20 (and toolchains support it).</div><div class=""><br class=""></div><div class="">We also want to reach out to the RedHat maintainers of libstdc++ to make sure we don’t adopt a weirdly different builtin.</div><div class=""><br class=""><br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On Oct 29, 2018, at 12:56 PM, will wray via cfe-dev <<a href="mailto:cfe-dev@lists.llvm.org" class="">cfe-dev@lists.llvm.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class=""><div class="">std::bit_cast was added to the C++ 20 draft this summer:</div><div class=""><a href="http://eel.is/c++draft/bit.cast" target="_blank" class="">http://eel.is/c++draft/bit.cast</a></div><br class="gmail-Apple-interchange-newline">In September JFB added a header with implementation (in llvm namespace):<br class="">llvm/include/llvm/ADT/bit.h<br class=""><br class=""> // This file implements the C++20 <bit> header.<br class=""> ...<br class=""> // - It isn't constexpr because that requires compiler support.<br class=""><div class=""><br class=""></div><div class="">What compiler support is it waiting on? What's the status?</div><div class=""><br class=""></div></div>
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