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From: kegs@provalid.com (Kent Dickey)
Newsgroups: comp.arch
Subject: Re: Arm ldaxr / stxr loop question
Date: Thu, 21 Nov 2024 05:46:56 -0000 (UTC)
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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
>>                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.
>
>Andrew.

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

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?

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.

Kent