Re: Stack analysis tool that really work?

From	Don Y <blockedofcourse@foo.invalid>
Newsgroups	comp.arch.embedded
Subject	Re: Stack analysis tool that really work?
Date	2021-08-07 10:26 -0700
Organization	A noiseless patient Spider
Message-ID	<semfoj$o70$1@dont-email.me> (permalink)
References	(10 earlier) <seiqoj$8mk$1@dont-email.me> <in5iifF4i5gU1@mid.individual.net> <sekf60$uvl$1@dont-email.me> <sekfad$uvl$2@dont-email.me> <in78kdFeu52U1@mid.individual.net>

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On 8/7/2021 4:20 AM, Niklas Holsti wrote:
> On 2021-08-07 2:06, Don Y wrote:
>> On 8/6/2021 4:04 PM, Don Y wrote:
>>>> That said, for some processors it is easy to recognize at decode-time most 
>>>> of the instructions that access the stack, and some versions of Bound-T let 
>>>> one specify different access times for stack accesses and for general 
>>>> (unclassified) accesses. That can be useful if the stack is located in fast 
>>>> memory, but other data are in slower memory.
>>>
>>> I'm thinking, specifically, about I/Os -- which are increasingly memory
>>> mapped (including register spaces).
>>
>> Sorry, I should be more clear.  I'm looking at the issues that would affect
>> *my* needs in *my* environment -- realizing these may be different than
>> those you've previously targeted.  (e.g., VMM, FPU emulation, etc.)
> 
> 
> Ok. If you describe your needs, perhaps I can comment.

I'm targeting some of the bigger ARM offerings -- A53/55.  My impression is
they go through more "contortions" to eke out additional performance than some
of the smaller processors.

> In my experience, access to memory-mapped registers tends to be not much slower 
> than access to memory. Also, quite often the addresses in MMIO accesses are 
> static or easy to derive in static analysis, so the WCET tool could choose the 
> proper access time, if the tool knows enough about the system architecture.

Yes, that last phrase being the kicker.  Can this be simplified to something
as crude as a "memory map"?

> If by "FPU emulation" you mean SW-implemented FP instructions, of course we 
> have encountered those. They are often hand-coded assembler with very complex 
> and tricky control flow, which makes it hard to find loop bounds automatically, 
> so manual annotations must be used instead.
> 
> What is VMM?

Virtual Memory Management.  I.e., when an opcode fetch (or argument reference)
can not only take longer than a cache miss... but *considerably* longer as
the physical memory is mapped in while the instruction stream "stalls".

[Note that a page fault need not map physical memory in the traditional sense.
It can also cause some "special" function to be invoked to provide the
requisite data/access.  So, the cost of a fault can vary depend on
*what* is faulting and which pager is handling that fault]

Thread

Stack analysis tool that really work? pozz <pozzugno@gmail.com> - 2021-07-29 18:22 +0200
  Re: Stack analysis tool that really work? Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-07-29 19:36 +0300
  Re: Stack analysis tool that really work? Don Y <blockedofcourse@foo.invalid> - 2021-08-02 17:56 -0700
    Re: Stack analysis tool that really work? Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-08-03 11:43 +0300
      Re: Stack analysis tool that really work? Don Y <blockedofcourse@foo.invalid> - 2021-08-03 02:28 -0700
        Re: Stack analysis tool that really work? Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-08-04 22:14 +0300
          Re: Stack analysis tool that really work? Don Y <blockedofcourse@foo.invalid> - 2021-08-04 15:43 -0700
    Re: Stack analysis tool that really work? pozz <pozzugno@gmail.com> - 2021-08-03 11:49 +0200
      Re: Stack analysis tool that really work? Don Y <blockedofcourse@foo.invalid> - 2021-08-03 20:17 -0700
        Re: Stack analysis tool that really work? pozz <pozzugno@gmail.com> - 2021-08-04 16:43 +0200
          Re: Stack analysis tool that really work? Don Y <blockedofcourse@foo.invalid> - 2021-08-04 11:06 -0700
            Re: Stack analysis tool that really work? Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-08-05 12:00 +0300
              Re: Stack analysis tool that really work? Don Y <blockedofcourse@foo.invalid> - 2021-08-05 04:54 -0700
      Re: Stack analysis tool that really work? Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-08-04 20:00 +0300
        Re: Stack analysis tool that really work? Don Y <blockedofcourse@foo.invalid> - 2021-08-04 10:50 -0700
          Re: Stack analysis tool that really work? Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-08-04 21:50 +0300
            Re: Stack analysis tool that really work? Don Y <blockedofcourse@foo.invalid> - 2021-08-04 15:46 -0700
              Re: Stack analysis tool that really work? Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-08-05 13:43 +0300
                Re: Stack analysis tool that really work? Don Y <blockedofcourse@foo.invalid> - 2021-08-05 06:16 -0700
                Re: Stack analysis tool that really work? Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-08-05 18:39 +0300
                Re: Stack analysis tool that really work? Don Y <blockedofcourse@foo.invalid> - 2021-08-06 01:09 -0700
                Re: Stack analysis tool that really work? Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-08-06 22:58 +0300
                Re: Stack analysis tool that really work? Don Y <blockedofcourse@foo.invalid> - 2021-08-06 16:04 -0700
                Re: Stack analysis tool that really work? Don Y <blockedofcourse@foo.invalid> - 2021-08-06 16:06 -0700
                Re: Stack analysis tool that really work? Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-08-07 14:20 +0300
                Re: Stack analysis tool that really work? Don Y <blockedofcourse@foo.invalid> - 2021-08-07 10:26 -0700
                Re: Stack analysis tool that really work? Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-08-07 20:46 +0300
                Re: Stack analysis tool that really work? Don Y <blockedofcourse@foo.invalid> - 2021-08-07 15:14 -0700
                Re: Stack analysis tool that really work? Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-08-07 14:09 +0300
                Re: Stack analysis tool that really work? Don Y <blockedofcourse@foo.invalid> - 2021-08-07 08:09 -0700
                Re: Stack analysis tool that really work? Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-08-07 19:50 +0300
                Re: Stack analysis tool that really work? Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-08-07 20:02 +0300
                Re: Stack analysis tool that really work? Don Y <blockedofcourse@foo.invalid> - 2021-08-07 10:34 -0700
                Re: Stack analysis tool that really work? Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-08-07 21:10 +0300
                Re: Stack analysis tool that really work? George Neuner <gneuner2@comcast.net> - 2021-08-06 22:55 -0400
                Re: Stack analysis tool that really work? Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-08-07 13:40 +0300
                Re: Stack analysis tool that really work? George Neuner <gneuner2@comcast.net> - 2021-08-08 18:34 -0400
                Re: Stack analysis tool that really work? Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-08-09 10:50 +0300
                Re: Stack analysis tool that really work? Paul Rubin <no.email@nospam.invalid> - 2021-08-09 11:26 -0700
                Re: Stack analysis tool that really work? Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-08-09 22:59 +0300
                Re: Stack analysis tool that really work? Don Y <blockedofcourse@foo.invalid> - 2021-08-09 12:04 -0700
          Re: Stack analysis tool that really work? Niklas Holsti <niklas.holsti@tidorum.invalid> - 2021-08-05 13:18 +0300
            Re: Stack analysis tool that really work? Don Y <blockedofcourse@foo.invalid> - 2021-08-05 04:59 -0700

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