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Date: Thu, 1 Oct 2015 10:18:25 +0100
From: Andrew Turner <andrew@fubar.geek.nz>
To: Stefan Parvu <sparvu@kronometrix.org>
Cc: "freebsd-arm@freebsd.org" <freebsd-arm@freebsd.org>
Subject: Re: compile kernel with hard float support
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On Thu, 1 Oct 2015 11:45:03 +0300
Stefan Parvu <sparvu@kronometrix.org> wrote:

> 
> I understood, by default, the image
> FreeBSD-armv6-11.0-RPI2-286947.img.gz has soft float support. All
> float-point operations are done in software not using the ARM hardware
> VFP. Correct ?

No, armv6 is built with softfp. This means the compiler is free to use
the VFP, but when passing floating-point data between functions it
needs to copy this to the general-purpose registers.

Even without this the helper functions detect the presence of the VFP
unit and make use of this when available.


> 
> If I want to build FreeBSD 11 with hard float support can I do this
> already ? Do we support hard float ? And how should I compile things ?
> 
> # setenv ARCH armv6hf (is this correct ?)
> # make buildkernel KERNCONF=RPI2

The kernel doesn't use any floating-point hardware, other than to
enable and disable it in the VFP driver. As such it doesn't matter if
you've built the kernel for hard-float or not, it will make no
difference to the code generated.

Andrew