On 08/02/2013 09:45 AM, Richard W.M. Jones wrote:
https://developer.android.com/training/articles/perf-tips.html#avoidfloat
there's no difference on modern hardware. (Note I didn't verify this.)
That's about the Dalvik implementation. Other comments on that page
suggest that it's so inefficient that a difference between float and
double argument passing and computation overhead might be lost in that
noise.
Hardware floating point operations except division should only take one
cycle, for both single and double precision. If VFP requires passing
double values in 32-bit register pairs, that might add some overhead,
though.
Judging by a google search for "qreal" "float" "arm" this difference
causes endless problems. I even found a Fedora build bug related to it.
However it's a matter for upstream to fix it. Not something we could
carry around only in Fedora IMHO.
I would expect that consistency across Fedora architectures is more
important than alignment to upstream.
--
Florian Weimer / Red Hat Product Security Team
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