[gentoo-user] -march=? for this cpu

[Nilesh Govindrajan]

I have two Gentoo VMs at Hetzner and the CPU supports 64 bit (grep lm 
/proc/cpuinfo = true).

But something funny, gcc -march=native -mtune=native -v -E - 2>&1 
</dev/null returns this:

Using built-in specs.
COLLECT_GCC=/usr/x86_64-pc-linux-gnu/gcc-bin/4.6.3/gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-pc-linux-gnu/4.6.3/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: 
/var/tmp/portage/sys-devel/gcc-4.6.3/work/gcc-4.6.3/configure 
--prefix=/usr --bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/4.6.3 
--includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.6.3/include 
--datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.6.3 
--mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.6.3/man 
--infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.6.3/info 
--with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.6.3/include/g++-v4 
--host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu --disable-altivec 
--disable-fixed-point --without-ppl --without-cloog --enable-lto 
--enable-nls --without-included-gettext --with-system-zlib 
--enable-obsolete --disable-werror --enable-secureplt --enable-multilib 
--enable-libmudflap --disable-libssp --enable-libgomp 
--with-python-dir=/share/gcc-data/x86_64-pc-linux-gnu/4.6.3/python 
--enable-checking=release --disable-libgcj --enable-libstdcxx-time 
--enable-languages=c,c++,fortran --enable-shared --enable-threads=posix 
--enable-__cxa_atexit --enable-clocale=gnu --enable-targets=all 
--with-bugurl=http://bugs.gentoo.org/ --with-pkgversion='Gentoo 4.6.3 
p1.11, pie-0.5.2'
Thread model: posix
gcc version 4.6.3 (Gentoo 4.6.3 p1.11, pie-0.5.2)
COLLECT_GCC_OPTIONS='-march=native' '-mtune=native' '-v' '-E'
  /usr/libexec/gcc/x86_64-pc-linux-gnu/4.6.3/cc1 -E -quiet -v - 
-march=pentium-m -mcx16 -msahf -mno-movbe -mno-aes -mno-pclmul -mpopcnt 
-mno-abm -mno-lwp -mno-fma -mno-fma4 -mno-xop -mbmi -mno-tbm -mno-avx 
-mno-sse4.2 -mno-sse4.1 --param l1-cache-size=32 --param 
l1-cache-line-size=64 --param l2-cache-size=4096 -mtune=generic
ignoring nonexistent directory "/usr/local/include"
ignoring nonexistent directory 
"/usr/lib/gcc/x86_64-pc-linux-gnu/4.6.3/../../../../x86_64-pc-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
  /usr/lib/gcc/x86_64-pc-linux-gnu/4.6.3/include
  /usr/lib/gcc/x86_64-pc-linux-gnu/4.6.3/include-fixed
  /usr/include
End of search list.
# 1 "<stdin>"
<stdin>:1:0: error: CPU you selected does not support x86-64 instruction set

It is returning pentium-m as architecture, which indeed is 32bit. I'm 
presently running the VM with -march=core2, but this is very weird.

This is the /proc/cpuinfo:

processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 2
model name      : QEMU Virtual CPU version 1.0
stepping        : 3
microcode       : 0x1
cpu MHz         : 3399.998
cache size      : 4096 KB
fpu             : yes
fpu_exception   : yes
cpuid level     : 4
wp              : yes
flags           : fpu de pse tsc msr pae mce cx8 apic sep mtrr pge mca 
cmov pse36 clflush mmx fxsr sse sse2 syscall nx lm rep_good nopl pni vmx 
cx16 popcnt hypervisor lahf_lm
bogomips        : 6799.99
clflush size    : 64
cache_alignment : 64
address sizes   : 40 bits physical, 48 bits virtual
power management:

Any idea what should be the march/mtune value?

-- 
Nilesh Govindarajan
http://nileshgr.com