Date: Wed, 1 Jul 2020 16:44:56 -0400 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Cc: Valentin Ochs <a@....de> Subject: Re: Superfluous shift in qsort()? On Wed, Jul 01, 2020 at 08:50:26PM +0200, Markus Wichmann wrote: > Hi all, > > I noticed something while reading code today: Near the end of qsort(), > we have this gem: > > shl(p, 2); > pshift -= 2; > p ^= 7; > shr(p, 1); > > Now, I don't know if I am missing something, but don't the shl and the > shr partially cancel out? Isn't this the same as > > shl(p, 1); > p ^= 3; > > As it is, it isn't wrong, just weird. Assuming non-overflow, I think they're equivalent (also assuming you keep the pshift-=2). I've CC'd the original author but we've not been in touch for a long time so I don't know whether to expect a response. I don't have any insight on why it was done this way. Rich
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