Re: [gentoo-user] USE="mmx mmxext sse sse2 ssse3 3dnow 3dnowext"

[Volker Armin Hemmann <volkerarmin@googlemail.com>]

On Freitag 29 Mai 2009, Graham Murray wrote:
> Stroller <stroller@stellar.eclipse.co.uk> writes:
> > But, surely "-march=" also instructs gcc to support the additional
> > instructions.  Suggest you re-read Daniel's post that I was replying
> > to.
> >
> > What's the difference between supporting the "certain set of
> > instructions" with "-march=" and doing so with USEs?
> >
> > Or doesn't "-march=" support additional "certain sets of
> > instructions". What does it do, then?
>
> I am not sure,
>
> $ gcc -Q --help=target -march=core2
> The following options are target specific:
>   -m128bit-long-double                  [disabled]
>   -m32                                  [enabled]
>   -m3dnow                               [disabled]
>   -m3dnowa                              [disabled]
>   -m64                                  [disabled]
>   -m80387                               [enabled]
>   -m96bit-long-double                   [enabled]
>   -mabm                                 [disabled]
>   -maccumulate-outgoing-args            [disabled]
>   -maes                                 [disabled]
>   -malign-double                        [disabled]
>   -malign-functions=
>   -malign-jumps=
>   -malign-loops=
>   -malign-stringops                     [enabled]
>   -march=                               core2
>   -masm=
>   -mavx                                 [disabled]
>   -mbranch-cost=
>   -mcld                                 [disabled]
>   -mcmodel=
>   -mcx16                                [disabled]
>   -mfancy-math-387                      [enabled]
>   -mfma                                 [disabled]
>   -mforce-drap                          [disabled]
>   -mfp-ret-in-387                       [enabled]
>   -mfpmath=
>   -mfused-madd                          [enabled]
>   -mglibc                               [enabled]
>   -mhard-float                          [enabled]
>   -mieee-fp                             [enabled]
>   -mincoming-stack-boundary=
>   -minline-all-stringops                [disabled]
>   -minline-stringops-dynamically        [disabled]
>   -mintel-syntax                        [disabled]
>   -mlarge-data-threshold=
>   -mmmx                                 [disabled]
>   -mms-bitfields                        [disabled]
>   -mno-align-stringops                  [disabled]
>   -mno-fancy-math-387                   [disabled]
>   -mno-fused-madd                       [disabled]
>   -mno-push-args                        [disabled]
>   -mno-red-zone                         [disabled]
>   -mno-sse4                             [enabled]
>   -momit-leaf-frame-pointer             [disabled]
>   -mpc
>   -mpclmul                              [disabled]
>   -mpopcnt                              [disabled]
>   -mpreferred-stack-boundary=
>   -mpush-args                           [enabled]
>   -mrecip                               [disabled]
>   -mred-zone                            [enabled]
>   -mregparm=
>   -mrtd                                 [disabled]
>   -msahf                                [disabled]
>   -msoft-float                          [disabled]
>   -msse                                 [disabled]
>   -msse2                                [disabled]
>   -msse2avx                             [disabled]
>   -msse3                                [disabled]
>   -msse4                                [disabled]
>   -msse4.1                              [disabled]
>   -msse4.2                              [disabled]
>   -msse4a                               [disabled]
>   -msse5                                [disabled]
>   -msseregparm                          [disabled]
>   -mssse3                               [disabled]
>   -mstack-arg-probe                     [disabled]
>   -mstackrealign                        [enabled]
>   -mstringop-strategy=
>   -mtls-dialect=
>   -mtls-direct-seg-refs                 [enabled]
>   -mtune=
>   -muclibc                              [disabled]
>   -mveclibabi=

get this:
dev.gentoo.org/~dirtyepic/bin/analyze-x86

and let it run, for example:
/analyze-x86 /bin/gzip
Checking vendor_id string... AuthenticAMD 64
Disassembling /bin/gzip, please wait...
i486:    0 i586:    0 ppro:   36 mmx:   46 3dnow:    0 ext3dnow:    0 sse:    
0 sse2:    4 sse3:    0
/bin/gzip will run on AMD Athlon64 or higher processor.

or this:
/analyze-x86 /bin/bash
Checking vendor_id string... AuthenticAMD 64
Disassembling /bin/bash, please wait...
i486:    0 i586:    0 ppro:  369 mmx:  876 3dnow:    0 ext3dnow:    0 sse:  
120 sse2:    0 sse3:    0
/bin/bash will run on Pentium III (pentium3) or higher processor.

and march=k8-sse3 -msse3 -O2 -pipe were my flags. Seems that a lot of stuff 
got turned on ;)

mplayer is even more 'interessting':
./analyze-x86 /usr/bin/mplayer
Checking vendor_id string... AuthenticAMD 64
Disassembling /usr/bin/mplayer, please wait...
i486: 3948 i586:   14 ppro: 7573 mmx: 164986 3dnow: 5331 ext3dnow:  768 sse: 
31407 sse2: 27712 sse3:   51

This binary was found to contain the cpuid instruction.
It may be able to conditionally execute instructions if
they are supported on the host (i586+).

/usr/bin/mplayer will run on AMD Athlon64 w/ SSE3 or higher processor.