On 07/14/2013 12:49 PM, Linus Torvalds wrote: > On Sun, Jul 14, 2013 at 12:30 PM, Tim Northover <t.p.northo...@gmail.com> > wrote: >> >> I don't think you've actually tested that, have you? (x86-64) > > Oh, you're right, for constants > 5 bits you have that other thing > going on. I didn't think about the fact that the constant changed in > the middle of the thread (it started out as 1). > > We use the gcc constraint "I" (0-31) in the kernel for this reason. > > Linus
This is also why the Intel manuals point out that "some assemblers" can take things like: bt[l] $63,(%rsi) ... and turn it into: btl $31,4(%rsi) This is definitely the friendly thing to do toward the human programmer. Unfortunately gas doesn't, nor does e.g. NASM. -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/