From time to time we get questions about floating point math on ARM
CPU’s. As it turns out this is a rather advanced topic that deserves
some discussion, so we recently put all of our notes and experiences into
a Wiki article that we felt was worth blogging about.
To make a long story short, many users get confused about the various
GNU Compiler (gcc) options for floating point. The most common
misconception is that ‘-mfloat-abi=softfp’ means that you are using
software floatingpoint math when in fact that produces binaries that
use hard float acceleration (as specified by the -mfp) agument but
with a function calling convention compatible with software floating
point. This allows the mixing of binaries and libraries that were
built for soft float vs hard float and is very useful if you are
trying to build a OS distribution that runs on a wide variety of
CPU’s. However, if you really want to squeeze the most out of your
ARM CPU that has hardware floating point support you can
achieve performance boosts (under most circumstances) by compiling
with -‘mfloat-abi=hard’ (which also means you will not be compatible
with binaries built with soft float). Also, keep in mind that your
Linux kernel must have VFP support if using hard float.
To see all the intricate details please visit our floating point wiki page
here:http://trac.gateworks.com/