On 05/14/2015 07:08 PM, Linus Torvalds wrote: > On Thu, May 14, 2015 at 10:05 AM, Linus Torvalds > <torva...@linux-foundation.org> wrote: >> >> I don't object to the patch, but did we actually confirm that it >> always overwrites all of %ecx? > > Just to clarify: I don't object to the patch because the code doesn't > actually end up *depending* on the high bits anyway, and does > word-sized compares etc. And the instruction size and speed things I > don't doubt. So it's just the commit message I wanted to check wrt > that whole "always overwrites all of %ecx". Because older CPU's didn't > necessarily (things like partial register writes are much less of an > issue when you're in-order and stupid ;)
This is 64-bit code, and all 64-bit CPUs zero-extend moves from segment registers. As you said, in this particular code it wouldn't matter anyway since subsequent code doesn't care about high bits of %ecx... -- 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/
