<html><head><meta http-equiv="Content-Type" content="text/html; charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><br class=""><div class=""><div><br class=""><blockquote type="cite" class=""><div class="">On Mar 11, 2021, at 10:43 AM, James Y Knight <<a href="mailto:jyknight@google.com" class="">jyknight@google.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class=""><div dir="ltr" class=""><br class=""></div><br class=""><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Thu, Mar 11, 2021 at 11:20 AM Sjoerd Meijer via cfe-dev <<a href="mailto:cfe-dev@lists.llvm.org" target="_blank" class="">cfe-dev@lists.llvm.org</a>> wrote:<br class=""></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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<span class="">In fact there is kind of awkward story behind this, we chose __fp16 rather than _Float16, major reason is GCC supporting, and also we saw ARM/AArch64 deprecated that for a while, but _Float16 problem still there in GCC, so we decide to using __fp16 rather
than _Float16.</span></div>
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<div class=""><span style="font-family: calibri, arial, helvetica, sans-serif; font-size: 12pt; background-color: rgba(0, 0, 0, 0);" class="">I am not really following this.</span><br class="">
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<span class="">And we also considering the compatible issue there, I mean the compatibility of ACLE's __fp16, __fp16 isn't a language extension for GCC, it's a target specific type for ARM/AArch64, so if we don't define that as a formal extension types, then we have
broken support/compiler compatibility issue on this due to GCC didn't support __fp16 as language extension.</span></div>
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And am not entirely sure about this.</div>
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I don't think I have changed my mind on this topic, and I don't know what else/more I can add to what I have already mentioned.</div>
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I won't repeat my arguments, but the bottom line is that we want to deprecate __fp16, while you like to rebrand it to a native half-precision type, and I don't see how this goes together very well. I also remain unconvinced about the arguments against _Float16,
which I think is the solution.<br class="">
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I don't know what your options are now. Maybe someone else can weigh in and shine a light on this, perhaps I am missing something. I don't know if you can go ahead and make these changes if you get an LGTM from someone else, but I hope the community sees the
problem of the same type behaving different on different targets.</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;" class=""><span style="font-family:Arial,Helvetica,sans-serif;font-size:small;color:rgb(34,34,34)" class=""></span></div></div></blockquote><div class=""><br class=""></div><div class="">I don't know why _Float16 isn't implemented by GCC in C++ mode, but I'd agree that using _Float16 for RISC-V, and adding support for _Float16 to GCC's C++ mode does seem like the better solution here, especially given that such support will also be needed for ARM.</div><div class=""><br class=""></div></div></div>
</div></blockquote></div><br class=""></div><div class=""><span style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class="">A thread has been started on the gcc mailing list. <a href="https://gcc.gnu.org/pipermail/gcc/2021-March/234962.html" class="">https://gcc.gnu.org/pipermail/gcc/2021-March/234962.html</a></span></div></body></html>