Hi. I stumbled upon this document when looking for a comparison between these compiling/toolchain infrastructures with regards to ARM targets.

http://llvm.org/devmtg/2011-09-16/EuroL ... lusARM.pdf

Sven

Interesting. Nowhere did it say any effort was going on to allow LLVM/clang to be used to compile the Linux kernel though...

I wonder what version they're talking about and when it'll be released, because the one on llvm.org is completely unusable for ARM in any sense.

One day I'd love to be able to build a Linux distro with a fully working ARMv7 LLVM compiler.. it's looking a few years away still though.

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Matt Sealey

according to http://en.wikipedia.org/wiki/Clang this happened in October 2010
3.0 is referenced which is scheduled to be released mid-November

I think it closer than that, but this isn't based on experience with the product.

Sven

Yeah, an x86 kernel, and there are still some big issues (read the ^22 article and the mail, early boot code is hosed, and several driver sets don't).

Compiling a kernel with minimal features, no crypto or checksumming in drivers, no netfilters or ip routing (therefore no firewalls or bridging) isn't really on my roadmap. And for ARM: it doesn't work, it doesn't even compile (let alone allowing the test for any broken code).

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Matt Sealey

Maybe for ARMv14. :)

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--

Science, n. Investigation of natural phenomena.
Engineering, n. Domestication of natural phenomena.
Technology, n. Domesticated natural phenomena.

--

\"It is essential for automatic computation that, instead of containing every single instruction necessary to carry out the program, the coded program include methods for generating instructions which are needed to carry out the program. ... One measure of the extent to which an automatic digital computer is used effectively is given by the ratio of the number of instructions formed in the machine to that of the instructions inserted into the machine initially.\" Mathematical Machines Volume I Digital Computers ©1961 Francis J. Murray

If so, then why is this ratio zero on most modern computer software?

There's a meta bug on llvm.org tracking the status of this: http://llvm.org/bugs/show_bug.cgi?id=4068.
Only (at least) 13 bugs left: http://llvm.org/bugs/showdependencytree ... resolved=1 :)

I'm quite impressed with LLVM. It seems to me to be a very promising technology.
For example, an OpenGL software rasterizer in early development, designed to leverage LLVM compiler technology is roughly 7 times faster than a decades old software rasterizer: http://zrusin.blogspot.com/2010/03/soft ... derer.html. Now that's impressive!

Not so easy, since LLVM developers usually supports just Mach-O (i.e. Darwin family), while ELF (Linux family) developers usually works on GCC...

Karel

It shouldn't be too much of a problem then since ELF is just an object format and it's the object code inside (which is arguably exactly the same no matter which container you put it in) that stops anyone from doing this, or more likely the code generation in the first place (lack of support for language features, processors and instruction sets..) rather than anything to do with the choice of operating system.

LLVM just doesn't do very well on ARM, where it works great on x86 and Linux in general..

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Matt Sealey

Well, LLVM running on ARM is more buggy than LLVM running on x86 and this also means that LLVM running on x86 cross-compiling to ARM produce probably less buggy code than LLVM running on ARM compiling to ARM. Unfortunately so far LLVM devs are most interested in x86->arm cross-compilation. Also some of linux specific issues are simply left unfixed due to Apple not putting priority on competitive OS... Ditto for ELF versus Mach-O which I mentioned above.

Well, well, LLVM looks like fantastic project, but, big BUT is that it's BSD licensed and Linux community does not endorse it that much -- at least so far! For Linux community notural choice is GPL hence you do have kind of license clash here... Completely different world exist in Apple domain of course, where LLVM is in the core of their devs plans. What do you thing compiles all the code for iOS including iOS itself? My bet is that it's just LLVM in cross-compilation mode (x86->ARM)...

Karel