On Mon, Aug 08, 2016 at 08:53:16PM +0200, Jiri Kosina wrote:
> Ville's patch is the proper thing to do; I still think the comments
> probably should be removed as they might provide more confusion than help,
> but that's a separate discussion.
Right, so while trying to debug this with a pen and paper, I found that
adding a subsript to the w variable makes it more understandable. I.e.,
something like this:
w_1 -= (w >> 1) & 0x55555555;
w_2 = (w_1 & 0x33333333) + ((w_1 >> 2) & 0x33333333);
and then you'd have
movl %eax, %edx # w
shrl %edx # w >>= 1
andl $0x55555555, %edx # (w >> 1) & 0x55555555
subl %edx, %eax # w_1 = w - ...
movl %eax, %edx # w_1
shrl $2, %eax # w_1 >>= 2
andl $0x33333333, %edx # (w_1 >> 2) & 0x33333333
andl $0x33333333, %eax # w_1 &= 0x33333333
addl %edx, %eax # w_2 = ... + ...
...
Anyway, something like that. I find that more readable TBH.
Thanks and thanks for confirming Ville's patch fixes it on your box.
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
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