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<div class="moz-cite-prefix">On 04/24/2015 12:29 PM, Diego Novillo
wrote:<br>
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<blockquote
cite="mid:CAD_=9DQnfRgXOUcK5RmXiH-4k-hF=FV6uOCpcP=S=urYDzCGuQ@mail.gmail.com"
type="cite">
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<div class="gmail_extra"><br>
<div class="gmail_quote">On Fri, Apr 24, 2015 at 3:28 PM,
Xinliang David Li <span dir="ltr"><<a
moz-do-not-send="true" href="mailto:davidxl@google.com"
target="_blank" class="cremed">davidxl@google.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">yes --
for count representation, 64 bit is needed. The branch
weight<br>
here is different and does not needs to be 64bit to
represent branch<br>
probability precisely.<br>
</blockquote>
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<div>Actually, the branch weights are really counts. They
get converted to frequencies. For frequencies, we don't
really need 64bits, as they're just comparative values
that can be squished into 32bits. It's the branch weights
being 32 bit quantities that are throwing off the
calculations.</div>
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</blockquote>
Having branch weights as 64 bit seems entirely reasonable to me.
Increasing the range of the value stored doesn't change the
semantics no matter how you interpret them. It does change the
calculated frequencies, but only to make them more accurate. I
don't see any problem with that. <br>
<br>
Philip<br>
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