Re: [TESTING]: ClangBSD branch needs testing before the import to HEAD

From: Alexander Kabaev <kabaev_at_gmail.com>
Date: Mon, 31 May 2010 15:32:01 -0400
On Mon, 31 May 2010 08:18:42 -0700
Steve Kargl <sgk_at_troutmask.apl.washington.edu> wrote:

> On Mon, May 31, 2010 at 05:07:44PM +0200, Dimitry Andric wrote:
> > On 2010-05-31 16:49, Steve Kargl wrote:
> > >> So, what exactly should we expect, if anything, to break? :)
> > > 
> > > Did you build and install new boot code?  ISTR that clang 
> > > can't compile src/sys/boot/i386/boot0 to the required 
> > > 512 bytes.
> > 
> > No, boot0 is written in assembly, and run through the regular (GNU)
> > assembler.  Neither gcc nor clang do anything more except calling
> > the linker.
> > 
> > The only component (in the whole clangbsd src tree) which still
> > needs to be compiled with gcc is boot2, which otherwise ends up
> > just a little too big, and doesn't fit.  This is being worked on,
> > but it isn't very critical, really.  Note that clangbsd
> > automatically uses gcc for this specific code, unless you override
> > it manually.
> 
> Doesn't this imply that clang/llvm isn't quite ready for deployment.
> Being able to boot a complete clang/llvm compiled FreeBSD system
> would seem to be critical.
> 
> When you say "This is being worked on", do you mean clang/llvm is
> being changed to compile boot2 or do you mean boot2 is being changed
> to allow clang/lvvm to compile it?
>  
FWIW, boot2 was a problem child for each and every GCC import on my
memory. Every single major GCC release has claimed better optimizations
and more compact generated code and yet they all inevitably generated
code which was appreciably bigger than code produced by previus GCC
version. This should not be used as an excuse to hold clang at bay,
provided base src still comes with working way for building the working
boot2 image (gcc).
 
-- 
Alexander Kabaev

Received on Mon May 31 2010 - 17:57:08 UTC

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