Unbreaking ports with n64 MIPS.
c.jayachandran at gmail.com
Tue Mar 20 14:54:14 UTC 2012
On Sat, Mar 17, 2012 at 9:14 AM, Juli Mallett <juli at clockworksquid.com> wrote:
> Hey Warner & others,
> Here's the patch I intend to commit in the near future, and then I'll
> add an UPDATING entry and send out an E-Mail blast to the list:
> I've decided not to make mips64eb (and mipseb and mipsn32eb) aliases,
> but I'm willing to be convinced to do so. It's a simple matter then
> to have a single regex in the few things that report the TARGET_ARCH
> or MACHINE_ARCH (e.g. GCC) that converts those aliases to the
> canonical values, and to otherwise just expand the regexes in this
> patch a little bit. We wouldn't report things with eb in them
> anywhere, and self-hosted builds would work, but it seems like we have
> a small enough community of MIPS users that this actually won't be a
> big deal. I'm willing to do the work on aliases, but only if there's
> strong requests.
The changes look fine. I can do native build of mips64 kernel, world
and ports on XLP, so let me know if need any help testing this.
> Two other things have come up on this thread:
> 1) n32 is an ABI not a sensible TARGET_ARCH. We need TARGET_ABI. We
> need GCC to report something like mips64-freebsdelf or freebsdelfn32
> or freebsdn32 or whichever. We need things to be able to detect that.
> Anyone who cares about n32 should really work on making it easy to
> use n32 worlds on n64 kernels. I'm happy to help with this as I have
> a pretty good idea where the pitfalls are, but it's non-trivial work,
> and involves putting conditionals all through the 32-bit compat code.
> For worlds, n32 should not be a TARGET_ARCH. Kernels should not be
> n32. And so on.
> 2) Soft- vs. hard-float. How should a user select? We used to have
> some way, I know, for x86 systems which needed soft float, so they
> didn't use the slower fp emulation in the kernel.
I think TARGET_CPUTYPE and TARGET_ARCH can be extended a bit to take
care of the most of these. Here's is my suggestion on how the
variables can work.
TARGET_CPUTYPE: Controls CPU specific optimization like soft-float
vs. hard-float and r1 vs r2 vs. extended instruction sets. mips32,
mips64 mips32r2, mips64r2, xlp(64r2+hardfloat),
octeon(64r2+softfloat) would be possible values for this.
The effect of these on different build targets would be -
kernel: builds kernel optimized for the CPU.
world: build a world optimized for the target CPU, the resulting
world will not work on other/lesser CPU types.
toolchain - not affected by this.
TARGET_ARCH: Controls ABI and endianness. Values are mips, mipsel,
mips64, mips64el, mipsn32, mipsn32el. Once we become tier 2, iinstall
binaries and ports should be available for each of these.
mips64: (default cpu - mips64r1 soft-float)
kernel: n64 (o32 binary support COMPAT_FREEBSD32 etc.)
userspace: n64 userspace and libraries, o32/n32? multilib support can be added
toolchain: generates binaries for default cpu type
mipn32 : (default cpu - mips64r1 soft-float)
kernel: n32 (with o32 elf binary support?)
user-space: n32 userspace, o32? multilib support
toolchain: default to n32 binaries
mips (default cpu type: mips32 r1, soft-float)
kernel - o32 elf binary support
userspace - o32
The only thing I see as an issue here is that if someone builds world
with a specialized CPUTYPE, they will not be able to use standard
ports binaries. This would mean that we would need to extend multi-lib
with CPU types.
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