Messages in this thread | | | Date | Fri, 28 Jun 2019 15:31:05 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH] perf/x86/intel: Mark expected switch fall-throughs |
| |
On Thu, Jun 27, 2019 at 09:12:50AM +0200, Peter Zijlstra wrote:
> Josh came up with the following: > > + /* If the jump target is close, do a 2-byte nop: */ > + ".skip -(%l[l_yes] - 1b <= 126), 0x66\n" > + ".skip -(%l[l_yes] - 1b <= 126), 0x90\n" > + /* Otherwise do a 5-byte nop: */ > + ".skip -(%l[l_yes] - 1b > 126), 0x0f\n" > + ".skip -(%l[l_yes] - 1b > 126), 0x1f\n" > + ".skip -(%l[l_yes] - 1b > 126), 0x44\n" > + ".skip -(%l[l_yes] - 1b > 126), 0x00\n" > + ".skip -(%l[l_yes] - 1b > 126), 0x00\n" > > Which is a wonderfully gruesome hack :-) So I'll be playing with that > for a bit.
For those with interest; full patches at:
https://lkml.kernel.org/r/20190628102113.360432762@infradead.org
| |