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Sorry, I noticed the patch first and left a comment there.</div>
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But repeating what I wrote there: you're redefining an existing type to behave as another type, but only for some targets. I think this is problematic and not going to help anyone. Your motivation is that the type you would like to use is not supported by GCC,
but that seems like the proper fix to me. <br>
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Cheers,</div>
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Sjoerd.<br>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> cfe-dev <cfe-dev-bounces@lists.llvm.org> on behalf of Kito Cheng via cfe-dev <cfe-dev@lists.llvm.org><br>
<b>Sent:</b> 05 March 2021 08:31<br>
<b>To:</b> Evandro Menezes <evandro.menezes@sifive.com>; Craig Topper <craig.topper@sifive.com>; Yi-Hsiu Hsu <yihsiu.hsu@sifive.com>; Kai Wang <kai.wang@sifive.com>; Zakk Chen <zakk.chen@sifive.com>; cfe-dev@lists.llvm.org <cfe-dev@lists.llvm.org><br>
<b>Subject:</b> [cfe-dev] [RFC] Having different behavior for __fp16 on RISC-V</font>
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<div><span style="color:rgb(0,0,0); font-family:"Segoe UI","Segoe UI Emoji","Segoe UI Symbol",Lato,"Helvetica Neue",Helvetica,Arial,sans-serif; font-size:13px">RISC-V has a draft extension for half-precision proposed last year[1],</span><br>
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so we think adding a new type for that would be great to make this<br>
easier to use that extension.</p>
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We found there is <tt style="background:rgba(71,87,120,0.1); padding:1px 4px; border-radius:3px; white-space:pre-wrap; line-break:anywhere; margin-top:0px">_Float16</tt> and <tt style="background:rgba(71,87,120,0.1); padding:1px 4px; border-radius:3px; white-space:pre-wrap; line-break:anywhere">__fp16</tt> types
are supported on GCC and<br>
Clang, but <tt style="background:rgba(71,87,120,0.1); padding:1px 4px; border-radius:3px; white-space:pre-wrap; line-break:anywhere">_Float16</tt> has C++ supporting issues on GCC site, so we think<br>
support both types is a reasonable choice to us.</p>
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However we would like have slight different behavior for <tt style="background:rgba(71,87,120,0.1); padding:1px 4px; border-radius:3px; white-space:pre-wrap; line-break:anywhere; margin-top:0px">__fp16</tt> other<br>
than ACLE: The evaluation format of <tt style="background:rgba(71,87,120,0.1); padding:1px 4px; border-radius:3px; white-space:pre-wrap; line-break:anywhere">__fp16</tt> set same as <tt style="background:rgba(71,87,120,0.1); padding:1px 4px; border-radius:3px; white-space:pre-wrap; line-break:anywhere">_Float16</tt>,<br>
which means no promotion are performed if there is no hardware half-precision<br>
supported.</p>
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The only concern to us is it's defined differnt with clang's document,<br style="margin-top:0px">
so we would put this RFC patch here, to make sure it's OK for make<br>
<tt style="background:rgba(71,87,120,0.1); padding:1px 4px; border-radius:3px; white-space:pre-wrap; line-break:anywhere">__fp16</tt> has differnt behavior between differnt targets.</p>
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This patch contains document change only, implementation would be in<br style="margin-top:0px">
other patches.</p>
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[1] <a href="https://github.com/riscv/riscv-isa-manual/pull/496" rel="noreferrer" target="_blank" style="text-decoration-line:none; color:rgb(19,108,178); margin-top:0px">https://github.com/riscv/riscv-isa-manual/pull/496</a><br>
[2] <a href="https://github.com/riscv/riscv-elf-psabi-doc/pull/172" rel="noreferrer" target="_blank" style="text-decoration-line:none; color:rgb(19,108,178)">https://github.com/riscv/riscv-elf-psabi-doc/pull/172</a></p>
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<div>Corresponding phabricator entry for this RFC:</div>
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<a href="https://reviews.llvm.org/D98012" target="_blank">https://reviews.llvm.org/D98012</a><br>
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