RS: [Beowulf] Sempron compile optimization

[Steffen Persvold]

> -----Original Message-----
> From: beowulf-bounces at beowulf.org [mailto:beowulf-bounces at beowulf.org] On
> Behalf Of Chris Samuel
> Sent: Wednesday, November 23, 2005 11:56 PM
> To: beowulf at beowulf.org
> Subject: Re: RS: [Beowulf] Sempron compile optimization
> 
> On Thursday 24 November 2005 03:43, Robert G. Brown wrote:
> 
> > Again, it was my understanding that if you run an x86_64 version of a
> > distro, the kernel, the libraries, and the applications are all compiled
> > with gcc which is ITSELF compiled for that architecture, and gcc
> > defaults to doing the right thing and linking the right libraries
> > automagically.
> 
> Not AMD64, but SuSE SLES 9 for PPC64 on Power5 the system supplied GCC
> outputs
> 32-bit code by default, you *must* specify -m64 if you want 64 bit
> objects.
> 
> $ arch
> ppc64
> $ gcc hello.c -o t1
> $ file t1
> t1: ELF 32-bit MSB executable, PowerPC or cisco 4500, version 1 (SYSV),
> for GNU/Linux 2.2.5, dynamically linked (uses shared libs), not stripped
> 

Yeah, a good rule of thumb for gcc is to specify -m64 or -m32, that way you
know what you're getting (on dual arch platforms). However, I do think it is
rather annoying that gcc on ppc64 produces 32bit binaries by default. I
believe the IBM compiler produce 64bit.

Cheers,
Steffen