CPUTYPE=native handling

[Alexander Best]

On Tue Nov  8 11, Dimitry Andric wrote:
> On 2011-11-08 22:04, Alexander Best wrote:
> ...
> > for me -march=native reports:
> > 
> > otaku% gcc -march=native -E -v - </dev/null
> > Using built-in specs.
> > Target: amd64-undermydesk-freebsd
> > Configured with: FreeBSD/amd64 system compiler
> > Thread model: posix
> > gcc version 4.2.2 20070831 prerelease [FreeBSD]
> >  /usr/libexec/cc1 -E -quiet -v -D_LONGLONG - -march=nocona -mtune=generic
> > #include "..." search starts here:
> > #include <...> search starts here:
> >  /usr/include/gcc/4.2
> >  /usr/include
> > End of search list.
> > # 1 "<stdin>"
> > # 1 "<built-in>"
> > # 1 "<command-line>"
> > # 1 "<stdin>"
> > 
> > where instead of nocona, core2 would have been the better choice:
> > 
> > [1.000000] CPU: Intel(R) Pentium(R) Dual  CPU  E2160  @ 1.80GHz (1800.00-MHz K8-class CPU)
> > [1.000000]   Origin = "GenuineIntel"  Id = 0x6fd  Family = 6  Model = f  Stepping = 13
> > [1.000000]   Features=0xbfebfbff<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,HTT,TM,PBE>
> > [1.000000]   Features2=0xe39d<SSE3,DTES64,MON,DS_CPL,EST,TM2,SSSE3,CX16,xTPR,PDCM>
> > [1.000000]   AMD Features=0x20100800<SYSCALL,NX,LM>
> > [1.000000]   AMD Features2=0x1<LAHF>
> > [1.000000]   TSC: P-state invariant, performance statistics
> 
> That's weird, the logic in gcc goes:
> 
>   cpuid (1, eax, ebx, ecx, edx);
> ...
>   has_ssse3 = !!(ecx & bit_SSSE3);
> ...
>           if (arch)
>             {
>               if (has_ssse3)
>                 cpu = "core2";
>               else if (has_sse3)
>                 {
>                   if (has_longmode)
>                     cpu = "nocona";
>                   else
>                     cpu = "prescott";
>                 }
>               else if (has_sse2)
>                 cpu = "pentium4";
>               else if (has_cmov)
>                 cpu = "pentiumpro";
>               else if (has_mmx)
>                 cpu = "pentium-mmx";
>               else if (has_cmpxchg8b)
>                 cpu = "pentium";
>               else
>                 cpu = "i386";
>             }
>           else
>             cpu = "generic";
>           goto done;
> 
> E.g. it seems to conclude your cpu *doesn't* have SSSE3, but does have
> long mode, and thus jumps to nocona.
> 
> You might be able to debug this, by putting some printfs in this
> function. :)

same on ref9-amd64.freebsd.org:

ref9-amd64% clang -march=native -### blabla.c
FreeBSD clang version 3.0 (trunk 135360) 20110717
Target: x86_64-unknown-freebsd9.0
Thread model: posix
 "/usr/bin/clang" "-cc1" "-triple" "x86_64-unknown-freebsd9.0" "-emit-obj" "-mrelax-all" "-disable-free" "-main-file-name" "tower.c" "-mrelocation-model" "static" "-mdisable-fp-elim" "-masm-verbose" "-mconstructor-aliases" "-munwind-tables" "-target-cpu" "core2" "-momit-leaf-frame-pointer" "-resource-dir" "/usr/bin/../lib/clang/3.0" "-ferror-limit" "19" "-fmessage-length" "275" "-fdiagnostics-show-option" "-fcolor-diagnostics" "-o" "/tmp/cc-ImChyq.o" "-x" "c" "tower.c"
 "/usr/bin/ld" "--eh-frame-hdr" "-dynamic-linker" "/libexec/ld-elf.so.1" "-o" "tower" "/usr/lib/crt1.o" "/usr/lib/crti.o" "/usr/lib/crtbegin.o" "-L/usr/lib" "/tmp/cc-ImChyq.o" "-lgcc" "--as-needed" "-lgcc_s" "--no-as-needed" "-lc" "-lgcc" "--as-needed" "-lgcc_s" "--no-as-needed" "/usr/lib/crtend.o" "/usr/lib/crtn.o"

BUT

ref9-amd64% gcc -march=native -E -v - </dev/null     
Using built-in specs.
Target: amd64-undermydesk-freebsd
Configured with: FreeBSD/amd64 system compiler
Thread model: posix
gcc version 4.2.2 20070831 prerelease [FreeBSD]
 /usr/libexec/cc1 -E -quiet -v -D_LONGLONG - -march=nocona -mtune=generic
#include "..." search starts here:
#include <...> search starts here:
 /usr/include/gcc/4.2
 /usr/include
End of search list.
# 1 "<stdin>"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "<stdin>"

cheers.
alex