Sven Barth wrote:
If someone wants to port the compiler to a new target processor it is
advisable to look whether there exists an OS that is already supported
by FPC, because then "only" the code generator and the CPU specific
parts of the RTL need to be implemented while the remaining RTL can be
reused which simplifies the first steps of the port. Otherwise you'd
need to implement the code generator and a more or less complete RTL.
So as Linux seems to be available at least for some variants of the CPU
I would strongly suggest to target Linux first and other OSes later.
Also the compile process of FPC is roughly this:
- for each used unit:
- parse the unit and generate a node tree for each
procedure/function/method (basically platform independant)
- generate a CPU specific linear assembler representation of each
node tree (this representation is independant of the specific assembler
used)
- if an external assembler (e.g. GNU as) is used: convert the
assembler lists to assembler files
- call the assembler (internal assemblers work on the assembler
lists directly) to generate the object file
- for external linkers (e.g. GNU ld): write a linkscript to instrument
the external linker
- call the linker (internal linkers work directly on the in memory
information the compiler has gathered)
Presumably that implies that it's not feasible to have an internal
assembler followed by a standard platform-specific linker. The reason I
highlight this combination is that I've had no success finding a free
assembler other than GNU as (gas) which covers all development
platforms, in particular "The free Tachyon Legacy Assembler is available
for MVS 3.8 and Linux/390" which obviously makes it NBG for the initial
stages of development on x86 Linux or Windows.
One of the links I posted earlier demonstrates that GCC is generally
tailored to suit the prevalent assembler on each operating system
(Linux, MUSIC/SP, CMS or whatever). That obviously doesn't imply that
the macro packages that serious assembler programmers would expect are
available.
--
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk
[Opinions above are the author's, not those of his employers or colleagues]
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