I'm preparing a DLL with AVX2 routines in FPC, since Delphi doesn't seem to have AVX2 support.

I wonder if it is possible to align constants used for shuffling (array[0..31] of byte typically) on 32-byte borders, so that I can use them directly in the code.

Till now I preloaded the constants using unaligned instructions before the loop, but I'm running out of registers in the current iteration.

(win64/x86_64 only btw, but I assume the possible data alignments aren't target dependent)

marcov wrote on Tue, 29 Nov 2016:

I wonder if it is possible to align constants used for shuffling (array[0..31] of byte typically) on 32-byte borders,

http://www.freepascal.org/docs-html/3.0.0/prog/progsu9.html

Jonas

Marco van de Voort wrote

'm preparing a DLL with AVX2 routines in FPC, since Delphi doesn't seem to have AVX2 support.

Very interesting. I will be pleased to compare it (on OS X) with Apple's Accelerate framework and with Intel's IPP lib <http://adriaan.biz/intel/ipp.pas.zip>.

But that is the code alignment, not the data alignment <http://www.freepascal.org/docs-html/3.0.0/prog/progsu1.html> ?

Also note that it is the OS that specifies the alignment on the stack, so you probably won't get 32-byte alignment for arrays on the stack.

Regards,

Adriaan van Os

It's for everything (there is no such thing as a "code constant" or "code variable"). The directive is named {$codealign xxx} because IIRC originally it only supported changing the alignment of procedures and jump targets.

Also note that it is the OS that specifies the alignment on the stack, so you probably won't get 32-byte alignment for arrays on the stack.

True, although that is a bug in the compiler (it should re-align the stack if necessary). I did not mention this, because FPC does not allow defining constants on the stack.

Jonas

In our previous episode, Jonas Maebe said:

> I wonder if it is possible to align constants used for shuffling > (array[0..31] of byte typically) on 32-byte borders, http://www.freepascal.org/docs-html/3.0.0/prog/progsu9.html

I skipped over it looking for a $dataalign. $codealign for dataalignement, a bit of a misnomer.

In our previous episode, Adriaan van Os said:

It's for work, and not (yet) open source. Mostly it is simple fare though, think debayering, rgb-to-rgba conversion, cmyk, color distance, abs difference of images, andmask etc. From my quick look at IPP that is mostly more complicated stuff.

In our previous episode, Marco van de Voort said:

Oh, and thanks, obviously :-)

Well, IPP can do the things you mention, apart from more complicated stuff.

Regards,

Adriaan van Os