Extended Description

Compiling with --march=native on one of my machines (a core 2 era Pentium Dual-Core) misidentifies the chip as penryn instead of core2 (the proper -march flag for this CPU)

Here's the output of gcc and clang for comparison, as well as /proc/cpuinfo for reference.

: | gcc -v -E -march=native -
Using built-in specs.
COLLECT_GCC=/usr/x86_64-pc-linux-gnu/gcc-bin/4.5.4/gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-pc-linux-gnu/4.5.4/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /var/tmp/portage/sys-devel/gcc-4.5.4/work/gcc-4.5.4/configure --prefix=/usr --bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/4.5.4 --includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.5.4/include --datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.5.4 --mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.5.4/man --infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.5.4/info --with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.5.4/include/g++-v4 --host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu --disable-altivec --disable-fixed-point --without-cloog --without-ppl --disable-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/4.5.4/python --enable-checking=release --enable-libstdcxx-time --enable-objc-gc --enable-languages=c,c++,java,objc,obj-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 4.5.4 p1.2, pie-0.4.7'
Thread model: posix
gcc version 4.5.4 (Gentoo 4.5.4 p1.2, pie-0.4.7)
COLLECT_GCC_OPTIONS='-v' '-E'
/usr/libexec/gcc/x86_64-pc-linux-gnu/4.5.4/cc1 -E -quiet -v - -D_FORTIFY_SOURCE=2 -march=core2 -mcx16 -msahf --param l1-cache-size=32 --param l1-cache-line-size=64 --param l2-cache-size=2048 -mtune=core2
ignoring nonexistent directory "/usr/local/include"
ignoring nonexistent directory "/usr/lib/gcc/x86_64-pc-linux-gnu/4.5.4/../../../../x86_64-pc-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
/usr/lib/gcc/x86_64-pc-linux-gnu/4.5.4/include
/usr/lib/gcc/x86_64-pc-linux-gnu/4.5.4/include-fixed
/usr/include
End of search list.

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COMPILER_PATH=/usr/libexec/gcc/x86_64-pc-linux-gnu/4.5.4/:/usr/libexec/gcc/x86_64-pc-linux-gnu/4.5.4/:/usr/libexec/gcc/x86_64-pc-linux-gnu/:/usr/lib/gcc/x86_64-pc-linux-gnu/4.5.4/:/usr/lib/gcc/x86_64-pc-linux-gnu/:/usr/lib/gcc/x86_64-pc-linux-gnu/4.5.4/../../../../x86_64-pc-linux-gnu/bin/
LIBRARY_PATH=/usr/lib/gcc/x86_64-pc-linux-gnu/4.5.4/:/usr/lib/gcc/x86_64-pc-linux-gnu/4.5.4/../../../../lib64/:/lib/../lib64/:/usr/lib/../lib64/:/usr/lib/gcc/x86_64-pc-linux-gnu/4.5.4/../../../../x86_64-pc-linux-gnu/lib/:/usr/lib/gcc/x86_64-pc-linux-gnu/4.5.4/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-v' '-E'

: | clang -v -E -march=native -
clang version 3.3 (tags/RELEASE_33/final)
Target: x86_64-pc-linux-gnu
Thread model: posix
"/usr/bin/clang" -cc1 -triple x86_64-pc-linux-gnu -E -disable-free -disable-llvm-verifier -main-file-name - -mrelocation-model static -mdisable-fp-elim -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -target-cpu penryn -target-linker-version 2.23.1 -v -resource-dir /usr/bin/../lib64/clang/3.3 -internal-isystem /usr/local/include -internal-isystem /usr/bin/../lib64/clang/3.3/include -internal-externc-isystem /include -internal-externc-isystem /usr/include -fdebug-compilation-dir /home/elena -ferror-limit 19 -fmessage-length 126 -mstackrealign -fobjc-runtime=gcc -fobjc-default-synthesize-properties -fdiagnostics-show-option -fcolor-diagnostics -backend-option -vectorize-loops -o - -x c -
clang -cc1 version 3.3 based upon LLVM 3.3 default target x86_64-pc-linux-gnu
ignoring nonexistent directory "/usr/local/include"
ignoring nonexistent directory "/include"
#include "..." search starts here:
#include <...> search starts here:
/usr/bin/../lib64/clang/3.3/include
/usr/include
End of search list.

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cat /proc/cpuinfo
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 23
model name : Pentium(R) Dual-Core CPU E5300 @ 2.60GHz
stepping : 10
microcode : 0xa07
cpu MHz : 2603.000
cache size : 2048 KB
physical id : 0
siblings : 2
core id : 0
cpu cores : 2
apicid : 0
initial apicid : 0
fpu : yes
fpu_exception : yes
cpuid level : 13
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx lm constant_tsc arch_perfmon pebs bts rep_good nopl aperfmperf pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm xsave lahf_lm dtherm tpr_shadow vnmi flexpriority
bogomips : 5188.99
clflush size : 64
cache_alignment : 64
address sizes : 36 bits physical, 48 bits virtual
power management:

processor : 1
vendor_id : GenuineIntel
cpu family : 6
model : 23
model name : Pentium(R) Dual-Core CPU E5300 @ 2.60GHz
stepping : 10
microcode : 0xa07
cpu MHz : 2603.000
cache size : 2048 KB
physical id : 0
siblings : 2
core id : 1
cpu cores : 2
apicid : 1
initial apicid : 1
fpu : yes
fpu_exception : yes
cpuid level : 13
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx lm constant_tsc arch_perfmon pebs bts rep_good nopl aperfmperf pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm xsave lahf_lm dtherm tpr_shadow vnmi flexpriority
bogomips : 5188.99
clflush size : 64
cache_alignment : 64
address sizes : 36 bits physical, 48 bits virtual
power management: