Re: gcc 4.3: when will it become standard compiler?

----- Original Message ----- 
From: "Christoph Mallon" <christoph.mallon_at_gmx.de>
To: "Andrew Reilly" <andrew-freebsd_at_areilly.bpc-users.org>
Cc: "Ollivier Robert" <roberto_at_keltia.freenix.fr>; 
<freebsd-current_at_freebsd.org>
Sent: Friday, January 09, 2009 10:06 AM
Subject: Re: gcc 4.3: when will it become standard compiler?


> Andrew Reilly schrieb:
>> On Fri, Jan 09, 2009 at 12:33:11AM +0100, Ollivier Robert wrote:
>>> According to O. Hartmann:
>>>> When will gcc 4.3 incorporated in FreeBSD 8 and become the standard
>>>> compiler suite? We figured out that gcc 4.3 does have a speed gain in
>>>> some numerical code of 3 - 8 % and I guess we can use this in the basic
>>>> OS as well ...
>>> I'd rather have llvm instead...
>>
>> I wouldn't mind that, either.  I've got the llvm port installed myself, 
>> in
>> preparation for doing some experiments of my own, but haven't tried using 
>> it to
>> build the kernel or user-land (or even any of the ports).  Has anyone 
>> given it a
>> go?  Is it missing any crucial features?  I believe that it had different 
>> (or
>> no?) support for PIC code generation, which could affect the ability to 
>> do
>> shared libraries, but recent release notes seem to indicate that that's 
>> been
>> addressed.
>
> One quite important difference between GCC and LLVM is that GCC has been 
> used to compile literally billions and billions of lines of code. Sure, 
> LLVM has compiled many lines, too, but it's hard to beat GCC in terms of 
> stability in this respect (yes, I am well aware that GCC had and has its 
> share of bugs). You have to do *lots* of testing before you can honestly 
> say that a compiler can really be used to compile a whole operating 
> system.
> Another aspect is that LLVM is in some parts more aggressive at 
> optimisation than GCC. So sloppy code, which GCC let you get away with, 
> may suddenly break - though it was wrong all along, but you just never 
> noticed. Of course the code has to be fixed, but this takes time.
> I'm not saying it's wrong to look for alternatives, but you cannot just 
> change your system compiler like you change underwear.
>
>> There's also someone working on a BSD-licenced retooling 
>> (ANSI/ISO-ification) of
>> the PCC compiler, which is getting close to being useful as a system 
>> compiler, I
>> believe. (http://www.ludd.ltu.se/~ragge/pcc/ in ports/lang/pcc)
>
> PCC cannot seriously be considered. Its design is stuck in the seventies. 
> From the point of view of compiler construction it is plain plain out of 
> question. I especially was amused by the statement of the author who 
> claimed PCC supports SSA - except for phi-functions.

Hi Current,

    I personally dont mind GCC being of a older version for the world and 
kernel compiles, however, I do wish that a newer version of binutils were 
used.

    I can compile GCC from the ports or download the sources and compile it 
there, but it seems to get really icky if you have two versions of binutils 
installed. The benifits of having the newer binutils is that I can compile 
using SSE4.1 which bomb out now due to the older "as" not knowing the new 
opcodes.

    I believe there are licenscing issues with using the newer binutils, but 
what they are I have no idea.

Peg