Re: [gentoo-user] Will a 64-bit-no-multilib machine cross-compile 32-bit code?

[Mike Gilbert <floppym@gentoo.org>]

On Mon, Mar 23, 2015 at 6:41 PM, Fernando Rodriguez
<frodriguez.developer@outlook.com> wrote:
> On Monday, March 23, 2015 6:18:46 PM Mike Gilbert wrote:
>> On Mon, Mar 23, 2015 at 9:51 PM, Walter Dnes <waltdnes@waltdnes.org> wrote:
>> > On Sun, Mar 22, 2015 at 09:25:53PM -0400, Fernando Rodriguez wrote
>> >
>> >> I guess gcc devs are careful when using the model numbers (Intel
>> >> lists 3 for Atoms, gcc uses only two so that may account for the
>> >> models I mentioned) but the chance of error is there. The -mno-xxx
>> >> flags would safeguard against it.
>> >
>> >   I have one of the earliest Atom chips.  Some people have a hard time
>> > believing this, but it's a 32-bit-only chip;  a couple of lines from
>> > /proc/cpuinfo
>> >
>> > model name      : Intel(R) Atom(TM) CPU Z520   @ 1.33GHz
>> > address sizes   : 32 bits physical, 32 bits virtual
>> >
>> >   Intel gives the CPU's specs at...
>> >
>> > http://ark.intel.com/products/35466/Intel-Atom-Processor-Z520-512K-Cache-1_33-GHz-533-MHz-FSB
>> >
>> > ...where it specifically says...
>> >
>> > Intel 64 # No
>> >
>> >   I want to make absolutely certain that "illegal instructions" are not
>> > compiled for it.
>>
>> You will probably need to add -m32 to CFLAGS to avoid building 64-bit
>> objects on the 64-bit machine.
>>
>
> Your CPU is an example of what I'm saying, not just because it doesn't have 64
> bit extensions but because it doesn't have MMX (at least according to the
> specs) and according to the GCC manual -march=atom means: "Intel Atom CPU with
> 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3 and SSSE3 instruction set
> support." So I guess it's more common than I thought.
>
> So you may also want to add -mno-mmx to be sure. GCC does check for mmx but it
> doesn't not use it on the output (probably a bug?).
>

It's much more likely that Intel's website doesn't bother including
MMX because it is so damn old that nobody cares.

/proc/cpuinfo would be a more reliable source of data.