On Aug 21, 2012, at 5:26 AM, Marius Strobl wrote: > On Mon, Aug 20, 2012 at 01:20:29PM -0600, Warner Losh wrote: >> >> On Aug 20, 2012, at 1:17 PM, Wojciech Puchar wrote: >> >>>>> or use ++. >>>>> >>>>> i think it is always aligned to 2 bytes and this should produce usable >>>>> code on any CPU? should be 6 instructions on MIPS and PPC IMHO. >>>> >>>> We should tag it as __aligned(2) then, no? If so, then the compiler >>>> should generate the code you posted. >>> should is the most important word in Your post. what it actually do - i >>> don't know. >> >> If we are requiring this to be __aligned(2), we should tag it as such to >> enforce this. >> >> Even without this tagging, the code to do a structure level copy of 6 bytes >> is going to be tiny... >> > > While the __aligned(2) approach certainly works, I've actually rather > mixed experiences on x86 with it as the compiler doesn't necessarily > produce the small and efficient one would expect from code it. Such > a change certainly shouldn't be done just on the assumption that the > compiler has all hints required to produce good code from it but the > resulting asm should be verified across all affected architectures.
Very true... I would have thought that went without saying... Warner_______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "freebsd-hackers-unsubscr...@freebsd.org"
