Re: (un)aligned accesses on x86 platform.

2010-03-17 Thread Mikael Pettersson
On Tue, 16 Mar 2010 06:50:30 -0800, H.J. Lu hjl.to...@gmail.com wrote: 2010/3/8 Pawe=C5=82 Sikora pl...@agmk.net: hi, during development a cross platform appliacation on x86 workstation i've enabled an alignemnt checking [1] to catch possible erroneous code before it appears on

Re: (un)aligned accesses on x86 platform.

2010-03-16 Thread H.J. Lu
2010/3/8 Paweł Sikora pl...@agmk.net: hi, during development a cross platform appliacation on x86 workstation i've enabled an alignemnt checking [1] to catch possible erroneous code before it appears on client's sparc/arm cpu with sigbus ;) it works pretty fine and catches alignment

Re: (un)aligned accesses on x86 platform.

2010-03-16 Thread Alexey Salmin
On Tue, Mar 16, 2010 at 9:05 PM, Tristan Gingold ging...@adacore.com wrote: On Mar 16, 2010, at 3:50 PM, H.J. Lu wrote: 2010/3/8 Paweł Sikora pl...@agmk.net: hi, during development a cross platform appliacation on x86 workstation i've enabled an alignemnt checking [1] to catch possible

Re: (un)aligned accesses on x86 platform.

2010-03-16 Thread Tristan Gingold
On Mar 16, 2010, at 4:37 PM, Alexey Salmin wrote: I am interested in an -mstrict-alignment option for x86. Not sure it will be useful. The libc still does unaligned accesses IIRC. Wow. What for? Well, simply because it is not compiled with strict alignment. There might also be some

Re: (un)aligned accesses on x86 platform.

2010-03-16 Thread Alexey Salmin
On Tue, Mar 16, 2010 at 9:48 PM, Tristan Gingold ging...@adacore.com wrote: On Mar 16, 2010, at 4:37 PM, Alexey Salmin wrote: I am interested in an -mstrict-alignment option for x86. Not sure it will be useful.  The libc still does unaligned accesses IIRC. Wow. What for? Well, simply

Re: (un)aligned accesses on x86 platform.

2010-03-16 Thread Piotr Wyderski
Alexey Salmin wrote: I always thought that unaligned access is much slower than aligned one. It is not *MUCH* slower, just slower (unless you cross cache line boundary). Unaligned accesses are very useful for improving performance of, among other things, certain hash functions (e.g. Paul

Re: (un)aligned accesses on x86 platform.

2010-03-16 Thread Jakub Jelinek
On Tue, Mar 16, 2010 at 10:04:04PM +0600, Alexey Salmin wrote: Wow. What for? Well, simply because it is not compiled with strict alignment.  There might also be some optimization in memory operation that does unaligned accesses. I always thought that unaligned access is much slower

(un)aligned accesses on x86 platform.

2010-03-08 Thread Paweł Sikora
hi, during development a cross platform appliacation on x86 workstation i've enabled an alignemnt checking [1] to catch possible erroneous code before it appears on client's sparc/arm cpu with sigbus ;) it works pretty fine and catches alignment violations but Jakub Jelinek had told me (on

Re: (un)aligned accesses on x86 platform.

2010-03-08 Thread Andrew Pinski
You define STRICT_ALIGNED to be 1 in i386.h or provide an option to turn that on/off like the rs6000 target does. Thanks, Andrew Pinski Sent from my iPhone On Mar 8, 2010, at 7:37 AM, Paweł Sikora pl...@agmk.net wrote: hi, during development a cross platform appliacation on x86

Re: (un)aligned accesses on x86 platform.

2010-03-08 Thread Richard Guenther
2010/3/8 Paweł Sikora pl...@agmk.net: hi, during development a cross platform appliacation on x86 workstation i've enabled an alignemnt checking [1] to catch possible erroneous code before it appears on client's sparc/arm cpu with sigbus ;) it works pretty fine and catches alignment

Re: (un)aligned accesses on x86 platform.

2010-03-08 Thread Paweł Sikora
On Monday 08 March 2010 16:46:10 Richard Guenther wrote: 2010/3/8 Paweł Sikora pl...@agmk.net: hi, during development a cross platform appliacation on x86 workstation i've enabled an alignemnt checking [1] to catch possible erroneous code before it appears on client's sparc/arm cpu