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Path: ...!Xl.tags.giganews.com!local-3.nntp.ord.giganews.com!nntp.supernews.com!news.supernews.com.POSTED!not-for-mail NNTP-Posting-Date: Thu, 21 Nov 2024 17:41:33 +0000 Sender: Andrew Haley <aph@zarquon.pink> From: aph@littlepinkcloud.invalid Subject: Re: Arm ldaxr / stxr loop question Newsgroups: comp.arch References: <vfono1$14l9r$1@dont-email.me> <YfxXO.384093$EEm7.56154@fx16.iad> <vh4530$2mar5$1@dont-email.me> <-rKdnTO4LdoWXKj6nZ2dnZfqnPWdnZ2d@supernews.com> <vhmhgg$h0qh$1@dont-email.me> User-Agent: tin/1.9.2-20070201 ("Dalaruan") (UNIX) (Linux/4.18.0-553.5.1.el8_10.x86_64 (x86_64)) Message-ID: <PdScnXGqwLpQ7aL6nZ2dnZfqn_ednZ2d@supernews.com> Date: Thu, 21 Nov 2024 17:41:33 +0000 Lines: 69 X-Trace: sv3-1Ln7SfvfOrJNq0r6Y7ho4CxVTUovulOO/ej8sK86S9aoRtPxqUwGpNuaIe1ZTaJGdN5Nh7EOi1fjcVp!Aghbz87VuRz+coXCi/PZEiGVmhBG0LiihodEvxU2jqqwzVu14LGRqnnfRH9Ne4t8hJobwizqpIdO!i0SpCca1 X-Complaints-To: www.supernews.com/docs/abuse.html X-DMCA-Complaints-To: www.supernews.com/docs/dmca.html X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly X-Postfilter: 1.3.40 Bytes: 4080 Kent Dickey <kegs@provalid.com> wrote: > In article <-rKdnTO4LdoWXKj6nZ2dnZfqnPWdnZ2d@supernews.com>, > <aph@littlepinkcloud.invalid> wrote: >>Kent Dickey <kegs@provalid.com> wrote: >> >>> Even better, let's look at the actual words for Pick Basic Dependency: >>> >>> --- >>> Pick Basic Dependency: >>> There is a Pick Basic dependency from an effect E1 to an effect >>> E2 if one of the following applies: >>> 1) One of the following applies: >>> a) E1 is an Explicit Memory Read effect You're right, they do seem to have forgotten to define Explicit Memory Read effect. I'm sure they meant to. >>> b) E1 is a Register Read effect >>> 2) One of the following applies: >>> a) There is a Pick dependency through registers and memory >>> from E1 to E2 >>> b) E1 and E2 are the same effect >> >>I don't understand this. However, here are the actual words: >> >>Pick Basic dependency >> >> A Pick Basic dependency from a read Register effect or read Memory >> effect R1 to a Register effect or Memory effect E2 exists if one >> of the following applies: >> >> . There is a Dependency through registers and memory from R1 to E2. >> . There is an Intrinsic Control dependency from R1 to E2. >> . There is a Pick Basic dependency from R1 to an Effect E3 and >> there is a Pick Basic dependency from E3 to E2. >> >>Seems reasonable enough in context, no? It's either a data dependency, >>a control dependency, or any transitive combination of them. > > Where did you get that from? I cannot find it in the current Arm document > DDI0487K_a_a-profile-architecture_reference_manual.pdf. Get it from > https://developer.arm.com/documentation/ddi0487/ka/?lang=en Err, the previous version of the same document. :-) > My text for Pick Basic dependency is a quote (where I label the lines > 1a,1b, etc., where it's just bullets in the Arm document) from page B2-239, > middle of the page. > > That sort of "summary" was exactly what I was asking for, but I don't see it, > so can you please name the page? B2-174 in DDI0487J > I'm pretty sure there are confusing typos all through this section > (E2 and E3 getting mixed up, for example), but that Pick Basic Dependency > was a doozy. > > It's likely the wording was better in an earlier document, I've noticed > this section getting more opaque over time. So it seems. I think everything in DDI0487J was meant to be there in DDI0487K, but it looks like it's all been macro-expanded and some things fell off the page, because reasons. I believe the author of the earlier, easier-to-read version of the Memory Model left Arm for another company. If it's any consolation, the version of the MM before he rewrote it was absolutely incomprehensible. Andrew.