time to write a compiler

| From: roman@gaudi.ccsf.caltech.edu (Roman Salvador)
|
| I would like to find out the time it takes (more or less) to write a
| compiler (i.e. a Fortran 90 one).


It depends on lots of different factors, such as:


the skill level and experience of the person(s) doing the
work;


the complexity of the language proper;


the complexity of the library (if provided);


the tools available;


doing 'just' a front end and using an existing back end, or
writing the whole ball of wax;


the target machine(s);


the desired optimization level(s).


As another data point, I wrote the front end for the Data General MV/Eclipse
C compiler from scratch to plug into the common language code generator and
optimizer. It took about 9 months from the start of the project until I had
a reasonable compiler (and another couple of years until it was rock solid).
I seem to recall the library took about 4-6 months for the first cut, but
since I didn't do much of this work, and we eventually rewrote a lot of it to
tie in with a UNIX emulation library developed elsewhere, I may be off on
this. I had a free hand in writing the front end, since the previous person
on the project had left before doing much code development and I nuked what
was left.


Some things that I remember about this:


I had to develop the compiler in PL/1, and it took some time
to learn the language.


I had to relearn C, since I had last used the V6 C compiler,
and the language had changed since then.


I was still a new programmer (I had graduated about 1-2 years
previously).


The parser generator that I used had some severe restrictions
in the early days, since it was originally run in 16-bit mode,
and could not handle 16 levels of precedence + the rest of C,
so I had to do operator precedence in PL/1 rather than in the
grammar.


The reference manual (K&R) had some subtle flaws in it (you
couldn't derive a function which returned a pointer to a
function and took some arguments from the grammar).


Convincing the code generator and optimizer to add new features
that C needed (notably the ?: operator).


Convincing the debugger to expand the common symbol table
format, to handle user defined types, and C specific items.


--
Michael Meissner email: meissner@osf.org phone: 617-621-8861
Open Software Foundation, 11 Cambridge Center, Cambridge, MA, 02142
--

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