Re: Compiler Flags problem with core2 CPU
[r...@meilk /usr/src/sys/i386/compile/AARON]# make CC='cc' make -f ../../../dev/aic7xxx/aicasm/Makefile MAKESRCPATH=../../../dev/aic7xxx/aicasm Warning: Object directory not changed from original /usr/src/sys/i386/compile/AARON cc -O2 -pipe -march=i686 -ffast-math -mfpmath=sse -O3 -nostdinc -I/usr/include -I. -I../../../dev/aic7xxx/aicasm -std=gnu99 -fstack-protector -Wsystem-headers -Werror -Wall -Wno-format-y2k -W -Wno-unused-parameter -Wstrict-prototypes -Wmissing-prototypes -Wpointer-arith -Wreturn-type -Wcast-qual -Wwrite-strings -Wswitch -Wshadow -Wcast-align -Wunused-parameter -Wchar-subscripts -Winline -Wnested-externs -Wredundant-decls -Wno-pointer-sign -c ../../../dev/aic7xxx/aicasm/aicasm.c cc1: warnings being treated as errors ../../../dev/aic7xxx/aicasm/aicasm.c:1: warning: SSE instruction set disabled, using 387 arithmetics *** Error code 1 It's interesting something can work with SSE instruction , while some are not , Warnings are treated as errors , if we can safely disable it in some specific occasions. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to freebsd-questions-unsubscr...@freebsd.org
Re: Compiler Flags problem with core2 CPU
On Tue, 2 Mar 2010 23:26:20 +0200, Dan Naumov dan.nau...@gmail.com wrote: See the section 3.17.14 Intel 386 and AMD x86-64 Options in the gcc Info manual. It contains a full list of the supported CPU-TYPE values for the -mtune=CPU-TYPE option. The -march=CPU-TYPE option accepts the same CPU types: `-march=CPU-TYPE' Generate instructions for the machine type CPU-TYPE. The choices for CPU-TYPE are the same as for `-mtune'. Moreover, specifying `-march=CPU-TYPE' implies `-mtune=CPU-TYPE'. Hello Out of curiosity, what is the optimal -march= value to use for the new Atom D510 CPU: http://ark.intel.com/Product.aspx?id=43098 ? I'm not sure. 'nocona' seems a pretty close match: _nocona_ Improved version of Intel Pentium4 CPU with 64-bit extensions, MMX, SSE, SSE2 and SSE3 instruction set support. Without actually trying -march=nocona on one of these I can't tell for sure if it is 'optimal' or not though. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to freebsd-questions-unsubscr...@freebsd.org
Re: Compiler Flags problem with core2 CPU
Aaron Lewis wrote:
[r...@meilk /usr/src/sys/i386/compile/AARON]# make
CC='cc' make -f ../../../dev/aic7xxx/aicasm/Makefile
MAKESRCPATH=../../../dev/aic7xxx/aicasm
Warning: Object directory not changed from original
/usr/src/sys/i386/compile/AARON
cc -O2 -pipe -march=i686 -ffast-math -mfpmath=sse -O3
[ ... ]
cc1: warnings being treated as errors
../../../dev/aic7xxx/aicasm/aicasm.c:1: warning: SSE instruction set
disabled, using 387 arithmetics
*** Error code 1
It's interesting something can work with SSE instruction , while some
are not , Warnings are treated as errors , if we can safely disable it in some
specific occasions.
Dude, the FreeBSD kernel doesn't use floating point, MMX, or SSE. See
sys/conf/kern.mk:
# [ ... ] Explicitly prohibit the use of SSE and other SIMD
# operations inside the kernel itself. These operations are exclusively
# reserved for user applications.
#
.if ${MACHINE_ARCH} == i386 ${CC} != icc
CFLAGS+=-mno-align-long-strings -mpreferred-stack-boundary=2 \
-mno-mmx -mno-3dnow -mno-sse -mno-sse2
INLINE_LIMIT?= 8000
.endif
Trying to override the default compiler flags to force it to use SSE is simply
not going to work.
--
-Chuck
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[SOLVED] Compiler Flags problem with core2 CPU
James Phillips wrote: I laughed at your question because I remember reading somewhere that using aggressive optimization options is a good way to find compiler bugs. I think that extends of optimizations for new CPU architectures as well. I also heard kernel code avoids MMX instructions for some reason: it may have to do with interrupt handling (fewer registers=faster?). x86 (and AMD64) processors are backwards compatible, so you don't strictly need the latest instructions. Regards, James Phillips Ah , i've just read it may not be safe to use MMX and SSE instructions in kernel code. So my CFLAGS is much too agressive , i'll notice this. Thank you all. -- Best Regards, Aaron Lewis - PGP: 0xA476D2E9 irc: A4r0n on freenode ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to freebsd-questions-unsubscr...@freebsd.org
Re: Compiler Flags problem with core2 CPU
On Sun, 28 Feb 2010 20:38:45 +0800, Aaron Lewis aaron.lewis1...@gmail.com wrote: Hi, I gonna recompile kernel for my core2 CPU , so i'd like to pass some flags to gcc. Kinds of -march=core2 , i tried to modify /etc/make.conf e.gCFLAGS += -march=core2 -O20 -ffast-math -mfpmath=sse But it fails .. bad arch switch , core2 cpu is not supported ? And is that useful to let gcc select cpu specified asm code ? See the section 3.17.14 Intel 386 and AMD x86-64 Options in the gcc Info manual. It contains a full list of the supported CPU-TYPE values for the -mtune=CPU-TYPE option. The -march=CPU-TYPE option accepts the same CPU types: `-march=CPU-TYPE' Generate instructions for the machine type CPU-TYPE. The choices for CPU-TYPE are the same as for `-mtune'. Moreover, specifying `-march=CPU-TYPE' implies `-mtune=CPU-TYPE'. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to freebsd-questions-unsubscr...@freebsd.org
Re: Compiler Flags problem with core2 CPU
On Sun, 28 Feb 2010 22:37:27 +0800, Aaron Lewis aaron.lewis1...@gmail.com wrote: Paul B Mahol wrote: On 2/28/10, Aaron Lewis aaron.lewis1...@gmail.com wrote: Hi, I gonna recompile kernel for my core2 CPU , so i'd like to pass some flags to gcc. Kinds of -march=core2 , i tried to modify /etc/make.conf e.gCFLAGS += -march=core2 -O20 -ffast-math -mfpmath=sse But it fails .. bad arch switch , core2 cpu is not supported ? It is bad idea to compile kernel with custom flags. And gcc in FreeBSD doesn't know about core2, use 'native' if you must. And is that useful to let gcc select cpu specified asm code ? Only for some userland stuff like openssl. Really ? It's bad to use custom flags to compile kernel , why do you think so ? I'd like to know more about this : ) So setting optimize compiler flags is only useful for userland stuff ? Please do not post your reply on *top* of the original text to this list. The preferred form of replying is bottom-posting here (other lists may have their own rules, but that's ok). I've fixed this message manually, but it would be nice if you posted your reply to the bottom of the quoted text. You can definitely *try* using optimizations for the kernel too. The FreeBSD developers and other users cannot _force_ you to use only a very limited set of options. You are more than free to try new things. This is precisely the reason why we make the source tree available to everyone, including detailed instructions for rebuilding the entire system from source. Note that the kernel is a very special program that may or may not work with some of the optimizations performed by higher GCC levels, though. There may be problems, so if you start building optimized kernels please make sure you keep a 'safe' backup copy of /boot/kernel before you install a new one. This way you will at least be able to boot into the old kernel if anything breaks. One way to keep a backup copy of the kernel is to make sure your /boot partition has enough free space and type as root: # cp -a /boot/kernel /boot/kernel.safe Then if anything goes wrong, you can always break into the loader prompt and type: boot unload boot set module_path=/boot/kernel.safe;/boot/modules boot load kernel boot boot -s Note that any optimization levels higher than the defaults are not 'supported' by the FreeBSD team though. As the warning in make.conf says [/usr/share/examples/etc/make.conf]: # CFLAGS controls the compiler settings used when compiling C code. # Note that optimization settings other than -O and -O2 are not recommended # or supported for compiling the world or the kernel - please revert any # nonstandard optimization settings to -O or -O2 -fno-strict-aliasing # before submitting bug reports without patches to the developers. So if you start building highly-optimized kernels and userland binaries, you are on your own. Bumping in any problem will require that you revert to the standard optimization flags, rebuild everything, try to reproduce the problem again and *then* report it. - Giorgos ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to freebsd-questions-unsubscr...@freebsd.org
RE: Compiler Flags problem with core2 CPU
See the section 3.17.14 Intel 386 and AMD x86-64 Options in the gcc Info manual. It contains a full list of the supported CPU-TYPE values for the -mtune=CPU-TYPE option. The -march=CPU-TYPE option accepts the same CPU types: `-march=CPU-TYPE' Generate instructions for the machine type CPU-TYPE. The choices for CPU-TYPE are the same as for `-mtune'. Moreover, specifying `-march=CPU-TYPE' implies `-mtune=CPU-TYPE'. Hello Out of curiosity, what is the optimal -march= value to use for the new Atom D510 CPU: http://ark.intel.com/Product.aspx?id=43098 ? Thanks - Sincerely, Dan Naumov ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to freebsd-questions-unsubscr...@freebsd.org
Re: Compiler Flags problem with core2 CPU
On 28 February 2010 07:38, Aaron Lewis aaron.lewis1...@gmail.com wrote: Hi, I gonna recompile kernel for my core2 CPU , so i'd like to pass some flags to gcc. Kinds of -march=core2 , i tried to modify /etc/make.conf e.g CFLAGS += -march=core2 -O20 -ffast-math -mfpmath=sse But it fails .. bad arch switch , core2 cpu is not supported ? Just so you know -O20 is the same as saying -O3. I don't think everything in base is safe for -ffast-math, but setting it in make.conf will surely test that. -O2 is already turned on almost everywhere by default, so also, I believe, with -fomit-frame-pointer. The only thing I've ever found to be remotely useful to change was -Os on an old, space-restricted machine. But last time I tried -Os on amd64 it broke. Badly. -- -- ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to freebsd-questions-unsubscr...@freebsd.org
Re: Compiler Flags problem with core2 CPU
Date: Sun, 28 Feb 2010 22:37:27 +0800 From: Aaron Lewis aaron.lewis1...@gmail.com Subject: Re: Compiler Flags problem with core2 CPU To: Paul B Mahol one...@gmail.com Cc: freebsd-questions@freebsd.org Message-ID: 4b8a7fa7.1070...@gmail.com Content-Type: text/plain; charset=ISO-8859-1; format=flowed Really ? It's bad to use custom flags to compile kernel , why do you think so ? I'd like to know more about this : ) So setting optimize compiler flags is only useful for userland stuff ? I laughed at your question because I remember reading somewhere that using aggressive optimization options is a good way to find compiler bugs. I think that extends of optimizations for new CPU architectures as well. I also heard kernel code avoids MMX instructions for some reason: it may have to do with interrupt handling (fewer registers=faster?). x86 (and AMD64) processors are backwards compatible, so you don't strictly need the latest instructions. Regards, James Phillips __ The new Internet Explorer® 8 - Faster, safer, easier. Optimized for Yahoo! Get it Now for Free! at http://downloads.yahoo.com/ca/internetexplorer/ ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to freebsd-questions-unsubscr...@freebsd.org
Compiler Flags problem with core2 CPU
Hi, I gonna recompile kernel for my core2 CPU , so i'd like to pass some flags to gcc. Kinds of -march=core2 , i tried to modify /etc/make.conf e.gCFLAGS += -march=core2 -O20 -ffast-math -mfpmath=sse But it fails .. bad arch switch , core2 cpu is not supported ? And is that useful to let gcc select cpu specified asm code ? -- Best Regards, Aaron Lewis - PGP: 0xA476D2E9 irc: A4r0n on freenode ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to freebsd-questions-unsubscr...@freebsd.org
Re: Compiler Flags problem with core2 CPU
On 2/28/10, Aaron Lewis aaron.lewis1...@gmail.com wrote: Hi, I gonna recompile kernel for my core2 CPU , so i'd like to pass some flags to gcc. Kinds of -march=core2 , i tried to modify /etc/make.conf e.gCFLAGS += -march=core2 -O20 -ffast-math -mfpmath=sse But it fails .. bad arch switch , core2 cpu is not supported ? It is bad idea to compile kernel with custom flags. And gcc in FreeBSD doesn't know about core2, use 'native' if you must. And is that useful to let gcc select cpu specified asm code ? Only for some userland stuff like openssl. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to freebsd-questions-unsubscr...@freebsd.org
Re: Compiler Flags problem with core2 CPU
Really ? It's bad to use custom flags to compile kernel , why do you think so ? I'd like to know more about this : ) So setting optimize compiler flags is only useful for userland stuff ? Paul B Mahol wrote: On 2/28/10, Aaron Lewis aaron.lewis1...@gmail.com wrote: Hi, I gonna recompile kernel for my core2 CPU , so i'd like to pass some flags to gcc. Kinds of -march=core2 , i tried to modify /etc/make.conf e.gCFLAGS += -march=core2 -O20 -ffast-math -mfpmath=sse But it fails .. bad arch switch , core2 cpu is not supported ? It is bad idea to compile kernel with custom flags. And gcc in FreeBSD doesn't know about core2, use 'native' if you must. And is that useful to let gcc select cpu specified asm code ? Only for some userland stuff like openssl. -- Best Regards, Aaron Lewis - PGP: 0xA476D2E9 irc: A4r0n on freenode ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to freebsd-questions-unsubscr...@freebsd.org
Re: Compiler Flags problem with core2 CPU
Do not top post. On 2/28/10, Aaron Lewis aaron.lewis1...@gmail.com wrote: Really ? It's bad to use custom flags to compile kernel , why do you think so ? I'd like to know more about this : ) Use google. So setting optimize compiler flags is only useful for userland stuff ? Paul B Mahol wrote: On 2/28/10, Aaron Lewis aaron.lewis1...@gmail.com wrote: Hi, I gonna recompile kernel for my core2 CPU , so i'd like to pass some flags to gcc. Kinds of -march=core2 , i tried to modify /etc/make.conf e.gCFLAGS += -march=core2 -O20 -ffast-math -mfpmath=sse But it fails .. bad arch switch , core2 cpu is not supported ? It is bad idea to compile kernel with custom flags. And gcc in FreeBSD doesn't know about core2, use 'native' if you must. And is that useful to let gcc select cpu specified asm code ? Only for some userland stuff like openssl. -- Best Regards, Aaron Lewis - PGP: 0xA476D2E9 irc: A4r0n on freenode ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to freebsd-questions-unsubscr...@freebsd.org
