[gentoo-dev] gcc vs tcc

[gentoo-dev] gcc vs tcc

[Per Wigren]

Is it OK to add dev-lang/tcc as a build-dependancy?
Compiling GOBO (http://www.gobosoft.com) with gcc 3.2.1 takes about 3 hours on 
my dual athlon 1.2Ghz with 512mb RAM...

Compare this:

oggy gexace # time gcc -O2 -o gexace-gcc gexace.c 
real	10m12.746s
user	9m33.227s
sys	0m4.897s
oggy gexace # time tcc -o gexace-tcc gexace.c 
real	0m1.353s
user	0m0.472s
sys	0m0.061s
oggy gexace # ls -l gexace-*
-rwxr-xr-x    1 root     root      1216938 Nov 29 18:27 gexace-gcc
-rwxr-xr-x    1 root     root       994200 Nov 29 18:27 gexace-tcc

It's almost silly! :)  I've done some just-for-fun benchmarking and found that 
tcc generates code about as fast as "gcc -O2", but is a little bit slower 
than "-O3" and even more so when adding things like "-fomit-frame-pointer" 
and "-ffast-math"... But the gobo-utilities are more I/O-intensive than 
CPU-intensive so it shouldn't matter much..

gexace is one of several huge (2mb+) .c-files that is part of gobo (generated 
by the eiffel-compiler).. Using tcc, compiling it will take about one minute 
while it takes 3 hours with gcc...

Regards,
Per Wigren


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Re: [gentoo-dev] gcc vs tcc

[Karl Trygve Kalleberg]

On Fri, 29 Nov 2002 18:41:12 +0100
Per Wigren <wigren@home.se> wrote:

> Is it OK to add dev-lang/tcc as a build-dependancy?

This makes for a _VERY_ interesting case. I think we should toy with this
concept a bit, as we can save ~3hrs compilation time (provided your
results are good, which I have all reason to think) and it's on a
non-critical package.

I suggest:
1) Only use tcc on platforms you have tested it on, so check ARCH and have
a 
x86? dev-lang/tcc-<version> in your DEPEND.
2) Only leave tcc in the DEPEND= and specifically exclude it in RDEPEND
(the assumption I make is that a tcc-compiled binary doesn't depend on a
tcc runtime); all too often, build-time tools end up in RDEPEND, which is
completely and utterly wrong.
3) Depending on how many packages can benefit from tcc, we may want to
introduce a useflag for it. May, as it increases the total maintenance
cost of the tree.

Have you done any tests to see how many of the "regular" packages compile
nicely with tcc ? Can we compile XFree with it ? (Obviously mozilla is not
a candidate, as it's largely written in C++).


Kind regards,

Karl T

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Re: [gentoo-dev] gcc vs tcc

[Per Wigren]

Friday 29 November 2002 19:43 skrev Karl Trygve Kalleberg:
> On Fri, 29 Nov 2002 18:41:12 +0100
>
> Per Wigren <wigren@home.se> wrote:
> > Is it OK to add dev-lang/tcc as a build-dependancy?
>
> This makes for a _VERY_ interesting case. I think we should toy with this
> concept a bit, as we can save ~3hrs compilation time (provided your
> results are good, which I have all reason to think) and it's on a
> non-critical package.
>
> I suggest:
> 1) Only use tcc on platforms you have tested it on, so check ARCH and have
> a x86? dev-lang/tcc-<version> in your DEPEND.

I only tested with a manual build of tcc-0.9.14.. The latest in portage is 
0.9.7 which is very outdated and 0.9.14 needs adding a #define in a file to 
make it compile on gcc 3.x so I think we should wait for 0.9.15 because that 
is already fixed in cvs so there will be no need for sed-hacking then... 

> 2) Only leave tcc in the DEPEND= and specifically exclude it in RDEPEND
> (the assumption I make is that a tcc-compiled binary doesn't depend on a
> tcc runtime); all too often, build-time tools end up in RDEPEND, which is
> completely and utterly wrong.

I know, I always do that. I'm also annoyed with people not separating 
DEPEND/RDEPEND...

> 3) Depending on how many packages can benefit from tcc, we may want to
> introduce a useflag for it. May, as it increases the total maintenance
> cost of the tree.

We should only try do it for packages that takes more than 10-15 minutes to 
compile on a fairly fast machine...

> Have you done any tests to see how many of the "regular" packages compile
> nicely with tcc ? Can we compile XFree with it ? (Obviously mozilla is not
> a candidate, as it's largely written in C++).

I don't know about XFree, but I don't think there should be a problem.. TCC 
supports 100% of ANSI-C, 90% of C99-specific things and the most common 
GCC-extensions.. I read somewhere that they pass all test but 10 or so in 
GCC's testsuite (which has THOUSANDS of tests!).. 

>
>
> Kind regards,
>
> Karl T
>
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> gentoo-dev@gentoo.org mailing list


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Re: [gentoo-dev] gcc vs tcc

[Sven Vermeulen]

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On Fri, Nov 29, 2002 at 06:41:12PM +0100, Per Wigren wrote:
> Is it OK to add dev-lang/tcc as a build-dependancy?
> Compiling GOBO (http://www.gobosoft.com) with gcc 3.2.1 takes about 3
> hours on 
> my dual athlon 1.2Ghz with 512mb RAM...
> 
> Compare this:
> 
> oggy gexace # time gcc -O2 -o gexace-gcc gexace.c 
> real	10m12.746s
> user	9m33.227s
> sys	0m4.897s
> oggy gexace # time tcc -o gexace-tcc gexace.c 
> real	0m1.353s
> user	0m0.472s
> sys	0m0.061s

Are you certain this is correct ? You did remove the created object-files (or
did a "make clean") before retrying with tcc, did you ?

Wkr,
	Sven Vermeulen

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Re: [gentoo-dev] gcc vs tcc

[George Shapovalov]

Hi guys.

Yes this would make for a very interesting investigation ;).

Just a small opinion here:

On Friday 29 November 2002 11:22, Per Wigren wrote:
> Friday 29 November 2002 19:43 skrev Karl Trygve Kalleberg:
> > On Fri, 29 Nov 2002 18:41:12 +0100
[skipped]
> I don't know about XFree, but I don't think there should be a problem.. TCC
> supports 100% of ANSI-C, 90% of C99-specific things and the most common
> GCC-extensions.. I read somewhere that they pass all test but 10 or so in
> GCC's testsuite (which has THOUSANDS of tests!)..

So this does have a potential for breakage in various packages. Even if it 
were 100% gcc compatible we shouldn't trust it without doing a really 
extensive testing. Besides many people will choose to have a "more coherent" 
system based solely on gcc and will be glad to pay the price in compile time. 
Therefore I think use of tcc should be made optional (even opt-in in the 
beginning if you ask me). New use flag suits this very well and I think is 
completely warranted (and for the same reason I do not like putting this into 
DEPEND). 

George



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Re: [gentoo-dev] gcc vs tcc

[Per Wigren]

Friday 29 November 2002 20:27 skrev Sven Vermeulen:
> On Fri, Nov 29, 2002 at 06:41:12PM +0100, Per Wigren wrote:
> > Is it OK to add dev-lang/tcc as a build-dependancy?
> > Compiling GOBO (http://www.gobosoft.com) with gcc 3.2.1 takes about 3
> > hours on
> > my dual athlon 1.2Ghz with 512mb RAM...
> >
> > Compare this:
> >
> > oggy gexace # time gcc -O2 -o gexace-gcc gexace.c
> > real	10m12.746s
> > user	9m33.227s
> > sys	0m4.897s
> > oggy gexace # time tcc -o gexace-tcc gexace.c
> > real	0m1.353s
> > user	0m0.472s
> > sys	0m0.061s
>
> Are you certain this is correct ? You did remove the created object-files
> (or did a "make clean") before retrying with tcc, did you ?
>
> Wkr,
> 	Sven Vermeulen

Yes it is correct! Believe it or not!
This is the result for wv after commenting away some stuff that tcc didn't 
want to compile, withouth caring if the result would work or not (tcc is MUCH 
stricter ANSI-C than GCC and this is just a compiletime-benchmark;))  :

# make distclean
# time X=$(export CC=gcc ; ./configure ; make)
real	1m45.230s
user	1m33.243s
sys	0m6.521s

# make distclean
# time X=$(export CC=tcc ; ./configure ; make)
real	0m9.065s
user	0m5.873s
sys	0m2.925s

# make distclean
# export CC=gcc
# ./configure
# time make >/dev/null
real	1m41.574s
user	1m30.151s
sys	0m4.611s

# make distclean
# export CC=tcc
# ./configure
# time make >/dev/null
real	0m6.369s
user	0m4.578s
sys	0m1.450s

Still not convinced? :)
Here is the gexace.c-file I used as an example earlier.. Try it yourself!
http://www.wigren.nu/gexace.c.bz2

Get the latest tcc from http://www.tinycc.org! You'll need to add
#define RTLD_DEFAULT    NULL
to the beginning of tccelf.c before compiling it with gcc 3.2.x!


BTW, notice the total size of the tcc archive.. 150K! :D


Regards,
Per Wigren


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Re: [gentoo-dev] gcc vs tcc

[Per Wigren]

Friday 29 November 2002 20:43 skrev George Shapovalov:
> Hi guys.
>
> Yes this would make for a very interesting investigation ;).

After investigating a little I found that it fails compiling something like 
95% or more of all packages without modification because it's so strictly 
ANSI-C, so tcc is not yet an option for most C-programs.. (If it compiles 
with "gcc -strict" it should compile with tcc) But for Eiffel (and other 
compile-to-c languages) I think it's really great because the c-code it 
generates is extremly fast ("unreadable optimized c-pseudo-assembler"), but 
takes a LONG LONG time to compile with gcc.. 

> Just a small opinion here:
>
> On Friday 29 November 2002 11:22, Per Wigren wrote:
> > Friday 29 November 2002 19:43 skrev Karl Trygve Kalleberg:
> > > On Fri, 29 Nov 2002 18:41:12 +0100
>
> [skipped]
>
> > I don't know about XFree, but I don't think there should be a problem..
> > TCC supports 100% of ANSI-C, 90% of C99-specific things and the most
> > common GCC-extensions.. I read somewhere that they pass all test but 10
> > or so in GCC's testsuite (which has THOUSANDS of tests!)..
>
> So this does have a potential for breakage in various packages. Even if it
> were 100% gcc compatible we shouldn't trust it without doing a really
> extensive testing. Besides many people will choose to have a "more
> coherent" system based solely on gcc and will be glad to pay the price in
> compile time. Therefore I think use of tcc should be made optional (even
> opt-in in the beginning if you ask me). New use flag suits this very well
> and I think is completely warranted (and for the same reason I do not like
> putting this into DEPEND).
>
> George

Agreed. But I still think gobo should be an exception.. 3 hours on my pretty 
fast machine vs a minute using tcc is a HUGE win! The Gobo tools are only 
used when compiling other Eiffel-packages anyway.. It contains 
Eiffel-replacements for C-stuff like flex, bison/yacc, cpp (preprocessor) and 
more.. It's not used at runtime..

// Wigren


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Re: [gentoo-dev] gcc vs tcc

[Karl Trygve Kalleberg]

On Sat, 30 Nov 2002 00:22:17 +0100
Per Wigren <wigren@home.se> wrote:

> Agreed. But I still think gobo should be an exception.. 3 hours on my
> pretty fast machine vs a minute using tcc is a HUGE win! The Gobo tools
> are only used when compiling other Eiffel-packages anyway.. It contains 
> Eiffel-replacements for C-stuff like flex, bison/yacc, cpp
> (preprocessor) and more.. It's not used at runtime..

Given the size of tcc itself, the huge win we can observe with gobo, and
the fact that gobo/eiffel is pretty esoteric even in Gentoo circles, I
think we should default to DEPEND="dev-lang/tcc-<version>" for now.

Eventually, it would be nice to have a tcc useflag, but if it's in reality
only applicable for this one package, there will be little use for it. As
tcc starts being able to compile other packages _AND_ those packages
exhibit a noticeable improvement in compilation time, I suggest we
introduce the useflag.

In the meantime, we should just make it easy for people to modify the
ebuild to not avail itself of tcc, for the people who feel a strong
loyalty towards gcc ;)

In time, it would of course be really, really sweet to have
package-specific useflags and package-specific default useflag settings,
so that we could do something like:

# emerge --show-options gobo
Useflag (default setting):
tcc (on)
whatever (off)
...

# USE="+tcc" emerge gobo

But that's for another time.


Kind regards,

Karl T

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Re: [gentoo-dev] gcc vs tcc

[Fernand Albarracin]

Hi,

On Sat 30 Nov 2002 at 00:51:59 +0100, Karl Trygve Kalleberg wrote:

> Given the size of tcc itself, the huge win we can observe with gobo, and
> the fact that gobo/eiffel is pretty esoteric even in Gentoo circles, I
> think we should default to DEPEND="dev-lang/tcc-<version>" for now.

> Eventually, it would be nice to have a tcc useflag, but if it's in reality
> only applicable for this one package, there will be little use for it. As
> tcc starts being able to compile other packages _AND_ those packages
> exhibit a noticeable improvement in compilation time, I suggest we
> introduce the useflag.

How about simply using an environnement variable such as CC ? The user
would set it in /etc/make.conf as he already does with CFLAGS and
friends. But he would propably do the following instead :

	CC=tcc; CFLAGS=-g; emerge stuff

CC would even allow to have multiple GCC version to choose from
(right?). And the best from a maintainer point of view: no
ebuild-specific work required.

Fernand

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Re: [gentoo-dev] gcc vs tcc

[Karl Trygve Kalleberg]

On Sat, 30 Nov 2002 01:30:40 +0100
Fernand Albarracin <fernand8@wanadoo.fr> wrote:

> Hi,
>
> How about simply using an environnement variable such as CC ? The user
> would set it in /etc/make.conf as he already does with CFLAGS and
> friends. But he would propably do the following instead :
> 
> 	CC=tcc; CFLAGS=-g; emerge stuff
> 
> CC would even allow to have multiple GCC version to choose from
> (right?). And the best from a maintainer point of view: no
> ebuild-specific work required.

In this case, the problem is that the user will have to be informed of
that _before_ doing the gobo compilation. As per ebuild rules, we are not
allowed to stop the build process and ask the user for input, so at best,
he'd see a notice scrolling by at high speed saying "this package would
take 2mins to compile if you have chosen tcc, but you haven't, too bad for
you".

I certainly agree with you that the CC=tcc is a nicer approach (perhaps
even the nicest approach of them all), but it requires the user to
actually _know_ he can benefit from using tcc on gobo beforehand. That's a
very steep requirement imho, given the fact that very few people have
heard of tcc, nobody's heard of gobo, and it's hardly commonplace to think
you can get a 30x improvement in compilation time just by switching
compilers :)


Kind regards,

Karl T

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