[M3devel] why this loop/multipass stuff

Wed Aug 22 16:41:09 CEST 2012

Jay I've been following what you've been writing with one eye.

But I'm not clear exactly what framework you're fitting into.  Are you
processing the output of m3front?

There's always m3tk.  Since it is claimed it was used to write a compiler
it ought to be able to process MODULEs but I've only ever used it to
process INTERFACEs.  What's the story about that?

    Mika

Tony Hosking writes:
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>Antony Hosking | Associate Professor | Computer Science | Purdue =
>University
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>Mobile +1 765 427 5484
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>On Aug 22, 2012, at 10:24 AM, Jay K <jay.krell at cornell.edu> wrote:
>
>> why this loop/multipass stuff
>>=20
>>=20
>> So people understand where I'm going here -- and Tony asked. I had =
>already written this up..
>>=20
>>=20
>>=20
>> 1) in the past working on m3cc/parse.c, I found that "declare"s
>> weren't always "topologically sorted".
>>=20
>>=20
>> That is, like, I might see:
>>=20
>> given TYPE T1 =3D INTEGER;
>> TYPE T2 =3D RECORD =3D a:T1; END;
>>=20
>>=20
>> I might have seen type T1 declared before T2, or not.
>> I'm not sure if it was record/fields or other relationships.
>> I just remember that building up a map of typeid to data, and
>> looking up it when needed, didn't always work, with one pass.
>>=20
>>=20
>> So what I did is that I was willing to "skip" declares
>> that referred to typeids I hadn't seen yet, and then loop
>> again, hoping for progress at each loop (fewer skips).
>
>Was this all in aid of building up proper type descriptors?
>
>> 2) It looks like declare_local/temp don't all come in
>> "at the start" of a procedure. I'm not sure if I'm generating
>> C or C++, but if I'm generating C, it helps to have declare_local/temp
>> right after begin_procedure/block. Multiple passes let me make that
>> so, without changing m3front.
>> (Upon further looking..it seems this is mostly done right, but
>> not for "try" blocks; maybe reasonable to change m3front here.).
>>=20
>>=20
>> Now, generating C++ is an option, and I'm ignoring all declares
>> currently anyway, so these don't force the matter, but:
>>=20
>>=20
>> 3) nested functions.
>> If a function contains any nested functions, I want to put all of
>> its locals in a local struct, and use the address of that struct
>> as the "static link". Or at least the locals that are referenced
>> by nested functions.
>
>Preferably these only, or else you will cause all locals to be in memory =
>instead of registers.
>
>> As well, m3front contains options as to
>> the order of outputing functions. It uses one order for m3back and
>> a different order for m3cc. I wouldn't mind if M3C.m3 worked either
>> way.
>>=20
>>=20
>> There are possibly other benefits that could be derived from multiple =
>passes.
>> Nothing offhand though.
>>=20
>>=20
>>  - Jay
>
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>0, 255); font-family: 'Gill Sans'; ">Antony =
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>style=3D"font-family: 'Gill Sans'; "> | Computer Science | Purdue =
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><br><div><div>On Aug 22, 2012, at 10:24 AM, Jay K <<a =
>href=3D"mailto:jay.krell at cornell.edu">jay.krell at cornell.edu</a>> =
>wrote:</div><br class=3D"Apple-interchange-newline"><blockquote =
>type=3D"cite"><div class=3D"hmmessage" style=3D"font-size: 12pt; =
>font-family: Calibri; font-style: normal; font-variant: normal; =
>font-weight: normal; letter-spacing: normal; line-height: normal; =
>orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: =
>none; white-space: normal; widows: 2; word-spacing: 0px; =
>-webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div =
>dir=3D"ltr">why this loop/multipass stuff<br><br><br>So people =
>understand where I'm going here -- and Tony asked. I had already written =
>this up..<br><br><br><br>1) in the past working on m3cc/parse.c, I found =
>that "declare"s<br>weren't always "topologically =
>sorted".<br><br><br>That is, like, I might see:<br><br>given TYPE T1 =3D =
>INTEGER;<br>TYPE T2 =3D RECORD =3D a:T1; END;<br><br><br>I might have =
>seen type T1 declared before T2, or not.<br>I'm not sure if it was =
>record/fields or other relationships.<br>I just remember that building =
>up a map of typeid to data, and<br>looking up it when needed, didn't =
>always work, with one pass.<br><br><br>So what I did is that I was =
>willing to "skip" declares<br>that referred to typeids I hadn't seen =
>yet, and then loop<br>again, hoping for progress at each loop (fewer =
>skips).<br></div></div></blockquote><div><br></div><div>Was this all in =
>aid of building up proper type descriptors?</div><br><blockquote =
>type=3D"cite"><div class=3D"hmmessage" style=3D"font-size: 12pt; =
>font-family: Calibri; font-style: normal; font-variant: normal; =
>font-weight: normal; letter-spacing: normal; line-height: normal; =
>orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: =
>none; white-space: normal; widows: 2; word-spacing: 0px; =
>-webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div =
>dir=3D"ltr">2) It looks like declare_local/temp don't all come in<br>"at =
>the start" of a procedure. I'm not sure if I'm generating<br>C or C++, =
>but if I'm generating C, it helps to have declare_local/temp<br>right =
>after begin_procedure/block. Multiple passes let me make that<br>so, =
>without changing m3front.<br>(Upon further looking..it seems this is =
>mostly done right, but<br>not for "try" blocks; maybe reasonable to =
>change m3front here.).<br><br><br>Now, generating C++ is an option, and =
>I'm ignoring all declares<br>currently anyway, so these don't force the =
>matter, but:<br><br><br>3) nested functions.<br>If a function contains =
>any nested functions, I want to put all of<br>its locals in a local =
>struct, and use the address of that struct<br>as the "static link". Or =
>at least the locals that are referenced<br>by nested =
>functions.</div></div></blockquote><div><br></div><div>Preferably these =
>only, or else you will cause all locals to be in memory instead of =
>registers.</div><br><blockquote type=3D"cite"><div class=3D"hmmessage" =
>style=3D"font-size: 12pt; font-family: Calibri; font-style: normal; =
>font-variant: normal; font-weight: normal; letter-spacing: normal; =
>line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: =
>0px; text-transform: none; white-space: normal; widows: 2; word-spacing: =
>0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; =
>"><div dir=3D"ltr">As well, m3front contains options as to<br>the order =
>of outputing functions. It uses one order for m3back and<br>a different =
>order for m3cc. I wouldn't mind if M3C.m3 worked =
>either<br>way.<br><br><br>There are possibly other benefits that could =
>be derived from multiple passes.<br>Nothing offhand =
>though.<br><br><br> - =
>Jay<br></div></div></blockquote></div><br></body></html>=
>
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