FreeBSD and LLVM
ed at 80386.nl
Wed May 21 17:23:54 UTC 2008
(CC'ing this back to the list)
* Stefan Esser <se at FreeBSD.org> wrote:
> this is great news! Can you provide your patches to upgrade the port
> to 2.3-pre?
I could, but I patched the ports rather poorly. The plists are
incorrect. I just incremented the version numbers, updated the distinfo
and made some changes to the llvm-gcc4 port to use the proper wrksrc.
> Did you, by chance, record build times with llvm-gcc compared to the
> system compiler?
> What about the quality of generated code (size, runtime)?
> Did you manage to get a meaning-ful program built that could be used
> as a benchmark?
I was able to compile a kernel with SMP disabled and PAE enabled. Other
combinations will not work. LLVM doesn't seem to be properly capable of
dealing with the xchg instruction in inline asm statements. A non-SMP
PAE kernel doesn't seem to use them :-)
Below are some build stats:
| 114.04s user 24.86s system 176% cpu 1:18.73 total
^ output of time(1)
| -rwxr-xr-x 1 ed wheel 4456839 May 21 12:59
^ output of ls -l kernel before stripping
| -rwxr-xr-x 1 ed wheel 3596008 May 21 13:16
^ output of ls -l kernel after stripping
| text data bss dec hex
| 3286323 229605 462280 3978208 3cb3e0
^ output of size(1) after stripping
| 119.04s user 22.64s system 178% cpu 1:19.27 total
| -rwxr-xr-x 1 ed wheel 4098317 May 21 12:33
| -rwxr-xr-x 1 ed wheel 3463448 May 21 12:57
| text data bss dec hex
| 3185574 220965 460216 3866755 3b0083
As you can see, compilation time is about the same, but the kernel image
is a little bigger. I don't know anything about the quality of the
> If 2.3-pre allows the kernel to boot and run, then many user-land
> programs should work as well. Testing a make world (and preparing
> the infrastructure to support llvm in addition to gcc and icc might
> be worthwhile ...).
We should really try that. Unfortunately I'm quite busy, hacking on the
TTY layer. ;-)
> You probably know about the clang project, which tries to completely
> replace the gcc parts needed for llvm-gcc ...
Yes. I haven't looked at it yet. It doesn't seem to be in Ports yet. Any
Ed Schouten <ed at 80386.nl>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Size: 195 bytes
Desc: not available
Url : http://lists.freebsd.org/pipermail/freebsd-hackers/attachments/20080521/501955bd/attachment.pgp
More information about the freebsd-hackers