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RE: crc32() optimization




> joakim.tjernlund@xxxxxxx.se said:
> >  Now I wonder: Is there a #pragma or something that will allow me to
> > unroll individual functions. I have looked allover but no luck so far.
> 
> You could add 'CFLAGS_crc32.o := -funroll-loops' to the Makefile. Not sure 
> how you'd manage it only for certain architectures. I suppose you could try 
> cetting CFLAGS_crc32.o in arch/$(ARCH)/Makefile. The name 'crc32.o' should 
> probably be unique -- anyone else with that file name should probably be 
> using the one in lib/ anyway :)

Nice, then it's at least possible to do it on file level.
I guess I should add 'CFLAGS_crc32.o := -funroll-loops' to lib/Makefile in
the 2.4 CRC backport for all arch's. I can't hurt anyone, right?

Still, it would be nice with an individual #pragma or something. 

> 
> Note that the new code in 2.5, which you're backporting, has the crc32
> functions in crc32.c; the old code had them inline so you'd actually need to
> use -funroll-loops on the whole jffs2 subdirectory.

Yup. I like the inline version. It will be more efficient for all those
constant length's crc32 calls in JFFS2. One could have both and test 
a compile time for a constant length and inline in those cases, but 
then you really need the #pragma thing, which seems to be nonexistent.

 Jocke


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