Alternatively, the JIT can read the content of these addresses and write them back as-is đ
> On Jul 5, 2017, at 09:01, Filip Pizlo <fpi...@apple.com> wrote: > > We should not use those helpers, especially in the JIT. It does not make > sense for the JIT to emit calls to system functions when the user is > expecting it to emit an instruction. If we cannot perfectly select the right > barrier on a particular CPU, we should disable concurrency on that CPU. > > -Filip > > On Jul 5, 2017, at 8:41 AM, JF Bastien <jfbast...@apple.com > <mailto:jfbast...@apple.com>> wrote: > >> On Linux you can do the following: >> ((void(*)())0xffff0fa0)(); >> >> That address contains a helper which does the ârightâ barrier, including if >> youâre not on an SMP system itâll do nothing. >> >> Details: >> https://www.kernel.org/doc/Documentation/arm/kernel_user_helpers.txt >> <https://www.kernel.org/doc/Documentation/arm/kernel_user_helpers.txt> >> That file also lists other Linux helpers. >> >> I think for ARMv6 it makes sense to use these helpers. AFAIK the mcr barrier >> instruction insât supported by all ARMv6 CPUs. >> >> For ARMv7 and later, DMB ish is the right thing. >> >> >>> On Jul 3, 2017, at 17:19, Caio Lima <ticaiol...@gmail.com >>> <mailto:ticaiol...@gmail.com>> wrote: >>> >>> Hi all. >>> >>> I'm working in this patch >>> (https://bugs.webkit.org/show_bug.cgi?id=172767 >>> <https://bugs.webkit.org/show_bug.cgi?id=172767>) and Mark Lam raised >>> some questions about the data memory barrier (DMB for short) in ARMv6 >>> using "mcr 15 ...". The point is that we are having divergences in ARM >>> official reference manual about the semantics of this instruction. We >>> have it discussed in the bug above and I would like to know if there >>> is somebody with stronger ARM background that could help us there and >>> then approve the patch to be committed. >>> >>> I thanks in advance and best regards, >>> Caio Lima. >>> _______________________________________________ >>> webkit-dev mailing list >>> webkit-dev@lists.webkit.org <mailto:webkit-dev@lists.webkit.org> >>> https://lists.webkit.org/mailman/listinfo/webkit-dev >>> <https://lists.webkit.org/mailman/listinfo/webkit-dev> >> >> _______________________________________________ >> webkit-dev mailing list >> webkit-dev@lists.webkit.org <mailto:webkit-dev@lists.webkit.org> >> https://lists.webkit.org/mailman/listinfo/webkit-dev >> <https://lists.webkit.org/mailman/listinfo/webkit-dev>
_______________________________________________ webkit-dev mailing list webkit-dev@lists.webkit.org https://lists.webkit.org/mailman/listinfo/webkit-dev
