From: Jon Steinhart <jon@fourwinds.com>
To: TUHS main list <tuhs@minnie.tuhs.org>
Subject: Re: [TUHS] A Reiser tour de force
Date: Fri, 01 Apr 2022 14:43:14 -0700 [thread overview]
Message-ID: <202204012143.231LhE2U3355821@darkstar.fourwinds.com> (raw)
In-Reply-To: <20220401194159.HF6gb%steffen@sdaoden.eu>
Steffen Nurpmeso writes:
> Jon Steinhart wrote in
> <202204011726.231HQFm03349496@darkstar.fourwinds.com>:
> |David Barto writes:
> |>> On Apr 1, 2022, at 8:59 AM, Douglas McIlroy <douglas.mcilroy@dartmouth.e\
> |>> du> wrote:
> |>> The recent discussion about Research choosing BSD's paging over
> |>> Reiser-London's brought to mind a stunning program by Reiser that
> |>> Research did adopt.
> |>>
> |>> A critical primitive in the Blit terminal was bitblt (block transfer
> |>> of a rectangular area). It was used ubiquitously, for example to
> ...
> |>> Bitblt got refined (i.e. elaborated) several times before Reiser did
> |>> away with it entirely. Instead he wrote a just-in-time generator of
> |>> optimal code. Thousands of distinct variants, which varied in size
> |>> from 16 to 72 bytes, could be produced by the same 400 lines of
> |>> assembler code.
> ...
> |> Does this exist for the rest of us to study?
> ...
> |It's not insanely complicated by modern standards. Without any knowledge
> |of other work, I did the same thing for a 68020 based graphics system where
> |the JIT code went into the I-cache and was amazingly fast for its day.
> |
> |If I remember correctly, things started with an outer-loop test to see
> |if there were overlapping regions to determine whether to go forward
> |to backwards to avoid having the destination trash the source.
> ...
>
> Only to add that "modern standard" C libraries define
> "overlapping" by means of exclusivity, meaning that memcpy(x,
> &x[1], 1) is an invalid overlapping that requires memmove() to be
> used.
Uh, yeah, but not relevant at least to the code I did which was written
in C but generated machine code, not calls to library functions.
next prev parent reply other threads:[~2022-04-01 21:45 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-01 15:59 Douglas McIlroy
2022-04-01 17:15 ` David Barto
2022-04-01 17:26 ` Jon Steinhart
2022-04-01 19:41 ` Steffen Nurpmeso
2022-04-01 21:29 ` Rob Pike
2022-04-01 21:31 ` Rob Pike
2022-04-01 21:43 ` Jon Steinhart [this message]
2022-04-03 11:22 Paul Ruizendaal via TUHS
2022-04-03 12:24 ` Rob Pike
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