On Wed, 29 May 2019 10:27:34 -0700 (PDT) Palmer Dabbelt <pal...@sifive.com> wrote:
> On Mon, 20 May 2019 02:44:18 PDT (-0700), aball...@gentoo.org wrote: > > On Sat, 18 May 2019 20:47:28 +0200 > > Michał Górny <mgo...@gentoo.org> wrote: > > > >> On Fri, 2019-05-03 at 23:34 +0200, Andreas K. Huettel wrote: > >> > * We will initially add two profiles to profile.desc: > >> > default/linux/riscv/17.0/rv64gc/lp64d (non-multilib, 64bit > >> > hardfloat) default/linux/riscv/17.0/rv64gc (multilib lp64d/lp64, > >> > i.e. hard/softfloat) > >> > >> I still don't understand the purpose of this multilib. If you have > >> a hardfloat CPU, why would you ever build some of the software > >> softfloat? > > > > One reason I could imagine is that the hardfloat isn't IEEE 754 > > compliant. Searching through the RISC-V spec, it does not seem to be > > the case here (ie: it is required to be compliant) so I'm also > > wondering what is the point here. > > The RISC-V floating-point extensions are IEEE-754 compliant, but > they're optional. We have chips without floating-point units, but > right now all the Linux capable chips have FPUs. As far as I know > there are no Linux binaries that anyone cares about that are compiled > for systems without hardware floating-point units, but I may be wrong > about that one. It was my understanding that FPU is not optional for rv64gc, is that correct ? > The non-FPU systems are much more interesting in embedded land, where > lots of users don't have FPUs. That's less relevant for Gentoo, but > I do use crossdev embedded toolchains. You'll probably not be using multilib here but rather a specific CHOST and/or flags to enable softfloat everywhere. [...] Alexis.
