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<div class="moz-cite-prefix">On 07/27/2018 03:20 AM, Matt Arsenault
via llvm-dev wrote:<br>
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cite="mid:28C22B96-0E62-4CB1-9513-B8BAE7D2B5C8@gmail.com">
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<div class="">On Jul 26, 2018, at 18:51, Stephen Canon via
llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org"
class="" moz-do-not-send="true">llvm-dev@lists.llvm.org</a>>
wrote:</div>
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<div class="" style="caret-color: rgb(0, 0, 0); font-family:
Helvetica; font-size: 12px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none;">ARMv8:</div>
<div class="" style="caret-color: rgb(0, 0, 0); font-family:
Helvetica; font-size: 12px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none;">1. FMIN / FMAX implement the new
minimum / maximum exactly.</div>
<div class="" style="caret-color: rgb(0, 0, 0); font-family:
Helvetica; font-size: 12px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none;">2. FMINNM / FMAXNM implement
minimumNumber / maximumNumber if we can prove no sNaNs are
present. If sNaN may be present, we need to canonicalize
each argument first.</div>
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<div>The AMDGPU instructions in the default mode for compute match
#2 here. They also do seem to preserve the new signed 0
behavior.</div>
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<div style="margin: 0px; font-stretch: normal; line-height:
normal;" class="">If we can settle on stating explicitly the in
the LangRef that de-facto current behavior where the
signalingness of a NaN is ignored here, that would allow solving
my immediate problems.</div>
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Given that I believe we don't generally support SNaN currently, this
seems consistent to me.<br>
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-Hal<br>
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<blockquote type="cite"
cite="mid:28C22B96-0E62-4CB1-9513-B8BAE7D2B5C8@gmail.com">
<div style="margin: 0px; font-stretch: normal; line-height:
normal;" class=""> The required lowering code would be clear and
optimizable. This isn’t ideal but at as far as the current
standard is concerned, this fits with sNaN being generally
broken in LLVM (e.g. constant folding for every operation
doesn’t bother quieting them)</div>
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<div class="">This is the only part that I immediately care about.
When the new standard is finalized, we can re-visit the other
details such as the signed 0 question. Are there any targets
that don’t already treat -0.0 as < 0.0?</div>
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normal;" class=""><br class="">
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<div style="margin: 0px; font-stretch: normal; line-height:
normal;" class="">-Matt</div>
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<pre class="moz-signature" cols="72">--
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory</pre>
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