Gentoo Forums
Gentoo Forums
Gentoo Forums
Quick Search: in
-march=native not enabling SSE instructions...when CPU suppo
View unanswered posts
View posts from last 24 hours

 
Reply to topic    Gentoo Forums Forum Index Portage & Programming
View previous topic :: View next topic  
Author Message
farrenheit
n00b
n00b


Joined: 20 Jun 2010
Posts: 29

PostPosted: Sat Jun 25, 2011 11:47 pm    Post subject: -march=native not enabling SSE instructions...when CPU suppo Reply with quote

:?: I have the Q6600 Intel Core2 Quad processor, which from various websites including wikipedia, should include instruction sets like SSE, SSE2, SSE3, etc.

But when I run the gcc code to display what -march=native does, it shows these instruction sets disabled. Anyone know why?

Code:
103904lksd etc # gcc -v -Q -march=native --help=target
Using built-in specs.
Target: x86_64-pc-linux-gnu
Configured with: /var/tmp/portage/sys-devel/gcc-4.4.5/work/gcc-4.4.5/configure --prefix=/usr --bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/4.4.5 --includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.4.5/include --datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.4.5 --mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.4.5/man --infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.4.5/info --with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.4.5/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-nls --without-included-gettext --with-system-zlib --disable-werror --enable-secureplt --enable-multilib --enable-libmudflap --disable-libssp --enable-libgomp --with-python-dir=/share/gcc-data/x86_64-pc-linux-gnu/4.4.5/python --enable-checking=release --disable-libgcj --enable-languages=c,c++ --enable-shared --enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu --with-bugurl=http://bugs.gentoo.org/ --with-pkgversion='Gentoo 4.4.5 p1.2, pie-0.4.5'
Thread model: posix
gcc version 4.4.5 (Gentoo 4.4.5 p1.2, pie-0.4.5)
COLLECT_GCC_OPTIONS='-v' '-Q'  '-fhelp=target'
 /usr/libexec/gcc/x86_64-pc-linux-gnu/4.4.5/cc1 -v help-dummy -D_FORTIFY_SOURCE=2 -march=core2 -mcx16 -msahf --param l1-cache-size=32 --param l1-cache-line-size=64 --param l2-cache-size=4096 -mtune=core2 -dumpbase help-dummy -auxbase help-dummy -version -fhelp=target -o /tmp/ccbUC7gd.s
The following options are target specific:
  -m128bit-long-double              [disabled]
  -m32                              [disabled]
  -m3dnow                           [disabled]
  -m3dnowa                          [disabled]
  -m64                              [enabled]
  -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                            [enabled]
  -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                            [enabled]
  -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=                           core2
  -muclibc                          [disabled]
  -mveclibabi=                      

COLLECT_GCC_OPTIONS='-v' '-Q'  '-fhelp=target'
 /usr/lib/gcc/x86_64-pc-linux-gnu/4.4.5/../../../../x86_64-pc-linux-gnu/bin/as -V -Qy -o /tmp/ccDvaYrJ.o /tmp/ccbUC7gd.s
GNU assembler version 2.20.1 (x86_64-pc-linux-gnu) using BFD version (GNU Binutils) 2.20.1.20100303
103904lksd etc #



...I feel like I'm being cheated if this processor supports all of these things and they are not being used. I like to compile everything optimized to my hardware to the extent possible.
Back to top
View user's profile Send private message
farrenheit
n00b
n00b


Joined: 20 Jun 2010
Posts: 29

PostPosted: Sun Jun 26, 2011 12:33 am    Post subject: Reply with quote

Well I looked around more and found someone mention the flag

Code:
-fverbose-asm


to check for detailed compile options when generating assembly code (using -S).

It does look like SSE and MMX are being used:


Code:
   .file   "CODE.c"
# GNU C (Gentoo 4.4.5 p1.2, pie-0.4.5) version 4.4.5 (x86_64-pc-linux-gnu)
#   compiled by GNU C version 4.4.5, GMP version 4.3.2, MPFR version 3.0.0-p3.
# GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
# options passed:  CODE.c -D_FORTIFY_SOURCE=2 -march=core2 -mcx16 -msahf
# --param l1-cache-size=32 --param l1-cache-line-size=64 --param
# l2-cache-size=4096 -mtune=core2 -auxbase-strip OUTG3 -O3 -fverbose-asm
# options enabled:  -falign-loops -fargument-alias
# -fasynchronous-unwind-tables -fauto-inc-dec -fbranch-count-reg
# -fcaller-saves -fcommon -fcprop-registers -fcrossjumping
# -fcse-follow-jumps -fdefer-pop -fdelete-null-pointer-checks
# -fdwarf2-cfi-asm -fearly-inlining -feliminate-unused-debug-types
# -fexpensive-optimizations -fforward-propagate -ffunction-cse -fgcse
# -fgcse-after-reload -fgcse-lm -fguess-branch-probability -fident
# -fif-conversion -fif-conversion2 -findirect-inlining -finline
# -finline-functions -finline-functions-called-once
# -finline-small-functions -fipa-cp -fipa-cp-clone -fipa-pure-const
# -fipa-reference -fira-share-save-slots -fira-share-spill-slots -fivopts
# -fkeep-static-consts -fleading-underscore -fmath-errno -fmerge-constants
# -fmerge-debug-strings -fmove-loop-invariants -fomit-frame-pointer
# -foptimize-register-move -foptimize-sibling-calls -fpeephole -fpeephole2
# -fpredictive-commoning -freg-struct-return -fregmove -freorder-blocks
# -freorder-functions -frerun-cse-after-loop -fsched-interblock
# -fsched-spec -fsched-stalled-insns-dep -fschedule-insns2 -fsigned-zeros
# -fsplit-ivs-in-unroller -fsplit-wide-types -fstrict-aliasing
# -fstrict-overflow -fthread-jumps -ftoplevel-reorder -ftrapping-math
# -ftree-builtin-call-dce -ftree-ccp -ftree-ch -ftree-copy-prop
# -ftree-copyrename -ftree-cselim -ftree-dce -ftree-dominator-opts
# -ftree-dse -ftree-fre -ftree-loop-im -ftree-loop-ivcanon
# -ftree-loop-optimize -ftree-parallelize-loops= -ftree-pre -ftree-reassoc
# -ftree-scev-cprop -ftree-sink -ftree-sra -ftree-switch-conversion
# -ftree-ter -ftree-vect-loop-version -ftree-vectorize -ftree-vrp
# -funit-at-a-time -funswitch-loops -funwind-tables -fvect-cost-model
# -fverbose-asm -fzero-initialized-in-bss -m128bit-long-double -m64 -m80387
# -maccumulate-outgoing-args -malign-stringops -mcx16 -mfancy-math-387
# -mfp-ret-in-387 -mfused-madd -mglibc -mieee-fp -mmmx -mno-sse4
# -mpush-args -mred-zone -msahf -msse -msse2 -msse3 -mssse3
# -mtls-direct-seg-refs


The second-to-last line shows those options being used. Not sure why the --help=target method listed these as disabled. Anyone know?
Back to top
View user's profile Send private message
Etal
Veteran
Veteran


Joined: 15 Jul 2005
Posts: 1829

PostPosted: Sun Jun 26, 2011 12:45 am    Post subject: Reply with quote

I remember reading about it somewhere that the help is misleading, but I can't remember the explanation or where I read it.

The only thing I could find was this wiki page saying that, as well as this one with a better way to see what gets enabled.
_________________
“And even in authoritarian countries, information networks are helping people discover new facts and making governments more accountable.”– Hillary Clinton, Jan. 21, 2010
Back to top
View user's profile Send private message
farrenheit
n00b
n00b


Joined: 20 Jun 2010
Posts: 29

PostPosted: Sun Jun 26, 2011 12:59 am    Post subject: Reply with quote

Thanks Etal. Very informative links.
Back to top
View user's profile Send private message
Etal
Veteran
Veteran


Joined: 15 Jul 2005
Posts: 1829

PostPosted: Sun Jun 26, 2011 1:29 am    Post subject: Reply with quote

By the way, I found it: http://gcc.gnu.org/ml/gcc-help/2009-04/msg00305.html
_________________
“And even in authoritarian countries, information networks are helping people discover new facts and making governments more accountable.”– Hillary Clinton, Jan. 21, 2010
Back to top
View user's profile Send private message
cach0rr0
Bodhisattva
Bodhisattva


Joined: 13 Nov 2008
Posts: 4123
Location: Houston, Republic of Texas

PostPosted: Thu Sep 22, 2011 4:27 pm    Post subject: Reply with quote

Etal wrote:
By the way, I found it: http://gcc.gnu.org/ml/gcc-help/2009-04/msg00305.html


That's what I, apparently badly, tried to explain here: https://forums.gentoo.org/viewtopic-t-895104.html#6820104

namely, this bit:

Quote:

from there, time to lookup what that specific march value supports


explained a bit better by the fella in that thread you posted:

Quote:

I assume you are asking whether the code will use SSE instructions if
appropriate. Yes, it will, because you specified -march with a
processor that supports SSE.

_________________
Lost configuring your system?
dump lspci -n here | see Pappy's guide | Link Stash
Back to top
View user's profile Send private message
Display posts from previous:   
Reply to topic    Gentoo Forums Forum Index Portage & Programming All times are GMT
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum