Re: [E-devel] libast from Eterm CVS fails to build with gcc4 on x86_64
Has anyone actually looked into why this is failing?
By the rules of Discreet Math/Boolean Algebra:
something xor something = 0
something_else xor 0 = something_else
so
valA ^ ( valA ^ valB ) = valB
If that is not working then you may have found a compiler bug (probably
in the register allocator). The appropriate output code should resemble
this (ATT syntax: op src, dest):
mov var_a, %r1
mov var_b, %r2
mov %r1, %r3
xor %r2, %r3
xor %r3, %r1
xor %r3, %r2
mov %r1, var_a
mov %r2, var_b
or optimized:
mov var_a, %r1
xor var_b, %r1
xor %r1, var_a
xor %r1, var_b
or load the values, manipulate the values, store the values. If
something happens in the middle of those steps, like the registers are
needed elsewhere (and not saved), then it will fail. The above code has
two memory fetches and two memory writes. Is it really faster than? :
mov var_a, %r1
mov var_b, %r2
mov %r2, var_a
mov %r1, var_b
without the type casting:
#define BINSWAP(a, b) ((a) ^= (b) ^= (a) ^= (b))
seems to rely on many compiler optimizations that aren't clearly
documented and may be defined differently for different architectures,
not to mention how different compilers will choose to deal with it.
Hence the failure on x86-64. For those curious compiling:
#define BINSWAP(a, b) \
(((long) (a)) ^= ((long) (b)) ^= ((long) (a)) ^= ((long) (b)))
int main( void )
{
long a = 3;
long b = 8;
asm( noop;noop;noop );
BINSWAP(a,b);
asm( noop;noop;noop );
}
yields:
noop;noop;noop
movq-16(%rbp), %rdx
leaq-8(%rbp), %rax
xorq%rdx, (%rax)
movq-8(%rbp), %rdx
leaq-16(%rbp), %rax
xorq%rdx, (%rax)
movq-16(%rbp), %rdx
leaq-8(%rbp), %rax
xorq%rdx, (%rax)
noop;noop;noop
If you enable -O[123] then you will need to use the values a b before
and after the BINSWAP call or they will be optimized away. And simply
using immediate values like I did will cause the compiler to simply set
the different registers that are used to access them in reverse order.
In other words the swap gets optimized out. The above code is without
-O and is clearly more complicated (by more than double) than it needs
to be.
Just my $0.02,
--
Tres
---
This SF.Net email is sponsored by Yahoo.
Introducing Yahoo! Search Developer Network - Create apps using Yahoo!
Search APIs Find out how you can build Yahoo! directly into your own
Applications - visit http://developer.yahoo.net/?fr=offad-ysdn-ostg-q22005
___
enlightenment-devel mailing list
enlightenment-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/enlightenment-devel
Re: [E-devel] libast from Eterm CVS fails to build with gcc4 on x86_64
Tres Melton wrote: Has anyone actually looked into why this is failing? By the rules of Discreet Math/Boolean Algebra: something xor something = 0 something_else xor 0 = something_else so valA ^ ( valA ^ valB ) = valB If that is not working then you may have found a compiler bug (probably in the register allocator). The appropriate output code should resemble this (ATT syntax: op src, dest): Tres, Its not the xor thats failing. Its the cast of the LHS of the assignments. The problem line in libast.h is: # define BINSWAP(a, b) (((long) (a)) ^= ((long) (b)) ^= ((long) (a)) ^= ((long) (b))) With gcc4 the following is invalid: int a=1, b=2; (long)a = (long)b; and that is the test I proposed for configure. I understand that this is a ISO C99 restriction and that gcc4 is just a bit more pedantic than gcc3. John --- This SF.Net email is sponsored by Yahoo. Introducing Yahoo! Search Developer Network - Create apps using Yahoo! Search APIs Find out how you can build Yahoo! directly into your own Applications - visit http://developer.yahoo.net/?fr=offad-ysdn-ostg-q22005 ___ enlightenment-devel mailing list enlightenment-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/enlightenment-devel
Re: [E-devel] libast from Eterm CVS fails to build with gcc4 on x86_64
On Thu, 2005-06-02 at 21:04 -0400, John Ellson wrote: Its not the xor thats failing. Its the cast of the LHS of the assignments. I understand now. Sorry for the confusion. -- Tres --- This SF.Net email is sponsored by Yahoo. Introducing Yahoo! Search Developer Network - Create apps using Yahoo! Search APIs Find out how you can build Yahoo! directly into your own Applications - visit http://developer.yahoo.net/?fr=offad-ysdn-ostg-q22005 ___ enlightenment-devel mailing list enlightenment-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/enlightenment-devel
Re: [E-devel] libast and eterm cvs
On Tuesday, 28 December 2004, at 17:59:11 (-0500),
Peter Hyman wrote:
Well, this was not easy for me, esp., since I am not the config guru.
HOWEVER, I found the problem that allowed me to complete configure,
although it still does not create a Makefile.
First, configure.in has an error
[EMAIL PROTECTED]:/mnt/src/libast$ automake -a -c
configure.in:91: required file `${srcdir}/include/libast/types.h.in' not
found
Turns out that for me, $srcdir is never defined, or taken as a literal.
I'm not the config guru, but changing:
$srcdir is defined by AC_INIT() in the configure script. It keys off
configure.in (thanks to AC_INIT(configure.in) of course) to see where
the sources are.
after mv .in config.h.in, I did a config.status --recheck and configure
completed normally.
However, Makefile still was not created. WHERE IS IT?
configure creates the Makefiles
Michael
--
Michael Jennings (a.k.a. KainX) http://www.kainx.org/ [EMAIL PROTECTED]
n + 1, Inc., http://www.nplus1.net/ Author, Eterm (www.eterm.org)
---
A woman broke up with me and sent me pictures of her and her new
boyfriend in bed together. Solution? I sent them to her dad.
-- Christopher Case
---
SF email is sponsored by - The IT Product Guide
Read honest candid reviews on hundreds of IT Products from real users.
Discover which products truly live up to the hype. Start reading now.
http://productguide.itmanagersjournal.com/
___
enlightenment-devel mailing list
enlightenment-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/enlightenment-devel
Re: [E-devel] libast and eterm cvs
On Tue, 2004-12-28 at 18:28 -0500, Michael Jennings wrote:
On Tuesday, 28 December 2004, at 17:59:11 (-0500),
Peter Hyman wrote:
Well, this was not easy for me, esp., since I am not the config guru.
HOWEVER, I found the problem that allowed me to complete configure,
although it still does not create a Makefile.
First, configure.in has an error
[EMAIL PROTECTED]:/mnt/src/libast$ automake -a -c
configure.in:91: required file `${srcdir}/include/libast/types.h.in' not
found
Turns out that for me, $srcdir is never defined, or taken as a literal.
I'm not the config guru, but changing:
$srcdir is defined by AC_INIT() in the configure script. It keys off
configure.in (thanks to AC_INIT(configure.in) of course) to see where
the sources are.
after mv .in config.h.in, I did a config.status --recheck and configure
completed normally.
However, Makefile still was not created. WHERE IS IT?
configure creates the Makefiles
That's my point. It doesn't! There is no Makefile.in.
Michael
--
Peter
---
SF email is sponsored by - The IT Product Guide
Read honest candid reviews on hundreds of IT Products from real users.
Discover which products truly live up to the hype. Start reading now.
http://productguide.itmanagersjournal.com/
___
enlightenment-devel mailing list
enlightenment-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/enlightenment-devel
Re: [E-devel] libast and eterm cvs
On Tue, 2004-12-28 at 20:07 -0500, Mike Frysinger wrote: On Tuesday 28 December 2004 07:40 pm, Peter Hyman wrote: That's my point. It doesn't! There is no Makefile.in. Makefile.in is generated by automake from Makefile.am and other magical files, configure generates Makefile from Makefile.in -mike I know it should. It does not. :( --- SF email is sponsored by - The IT Product Guide Read honest candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://productguide.itmanagersjournal.com/ ___ enlightenment-devel mailing list enlightenment-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/enlightenment-devel -- Peter --- SF email is sponsored by - The IT Product Guide Read honest candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://productguide.itmanagersjournal.com/ ___ enlightenment-devel mailing list enlightenment-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/enlightenment-devel
Re: [E-devel] libast and eterm cvs
On Tuesday 28 December 2004 05:59 pm, Peter Hyman wrote: Well, this was not easy for me, esp., since I am not the config guru. take a step back why are you running these autotools yourself ? why arent you running `./autogen.sh` ? as you showed somewhere in a previous e-mail, you're attempting to use autotools that may just be a little too new ;) -mike --- SF email is sponsored by - The IT Product Guide Read honest candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://productguide.itmanagersjournal.com/ ___ enlightenment-devel mailing list enlightenment-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/enlightenment-devel
Re: [E-devel] libast and eterm cvs
On Tuesday, 28 December 2004, at 19:40:34 (-0500), Peter Hyman wrote: configure creates the Makefiles That's my point. It doesn't! There is no Makefile.in. Peter, This is why these tools are less-than-affectionately known around here as autoFUCK. There's very little consistency between versions, and they often cause just as many problems as they solve. I can't spend a bunch of time diagnosing auto* errors for you. My advice is to download the tarballs from eterm.org since the files generated by auto* are already there. Needless to say, I can't reproduce your problem here. :) Michael -- Michael Jennings (a.k.a. KainX) http://www.kainx.org/ [EMAIL PROTECTED] n + 1, Inc., http://www.nplus1.net/ Author, Eterm (www.eterm.org) --- Whoa. Somebody computer programmers think is anti-social? That I'd like to see.-- Sydney Penny, Hyperion Bay --- SF email is sponsored by - The IT Product Guide Read honest candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://productguide.itmanagersjournal.com/ ___ enlightenment-devel mailing list enlightenment-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/enlightenment-devel
