[fpc-devel] On a port of Free Pascal to the IBM 370

Mark Morgan Lloyd markMLl.fpc-devel at telemetry.co.uk
Wed Jan 18 10:46:42 CET 2012

michael.vancanneyt at wisa.be wrote:
> On Wed, 18 Jan 2012, Michael Schnell wrote:
>> AFAI learned:
>> I suppose the code generator should be doable, regarding that there 
>> already are several supported CPUs. At least a working compiler might 
>> come into existence in a decent amount of time, adding optimizations 
>> is another project.
>> OTOH I suppose that a porting the RTL to a mainframe OS will not be 
>> easy and without this the compiler is quite useless.
> I do not think it is more difficult than any other OS.

I've got reservations because of the EBCDIC issue. My own opinion is 
that this effort would be far better targeting Linux on a comparatively 
recent model of machine, since these are well-supported by the Hercules 
emulator which gives developers an absolutely standard working 
environment: which is, obviously, why I wrote it up a few months ago.

I'm sure Paul has his reasons that we all need to respect, but I don't 
think that using a 370 emulator (i.e. at least two architectures out of 
date) plus an obsolete operating system is the place to start.

I admit to having considered this as a long-term project, but what I 
don't have is a good understanding of the architecture's assembler-level 
programming. However I think I need to make the general point here that 
"IBM Assembler" is understood in the industry to encompass that which is 
needed to write application-level programs in CISC assembler (plus macro 
support etc.), and that even somebody skilled in that particular black 
art might need to enter unfamiliar territory when it comes to the 
operations required by a compiler's code generation (e.g. commercial 
programming doesn't do large amounts of stack-relative addressing).

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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