On 2013-01-15 18:33, Clem Cole wrote:
On Tue, Jan 15, 2013 at 12:05 PM, Johnny Billquist <bqt at softjar.se
<mailto:bqt at softjar.se>> wrote:
Right. I'm sure that with enough work, you can always do it, but I'm
curious on how much work. I have a feeling that compilers written in
high level languages rapidly expand their requirements...
Its not that actually - IMHO. You can always use overlays and thunks
to write code that works on a small address machines, like the PDP-11.
I think the problem is that people that used / wanted the language did
not need all of the features and frankly time moved on. The languages
themselves were just too heavy not the compiler per say - the compilers
became heavy to support the language features people wanted.
If PL/M or PL/360 had not lost to C (BCPL et al), it might have been
different in the case of PL/1. If you note sub-set C compilers for the
8 and 16 bit machines exist or often exist as cross compilers from
larger systems.
The issue is that 16-bits of data space is >>very<< limiting for a
programmer, the code space can be swapped in and out with automatic or
managed overlays - but data space is much harder to do.
But I'm not talking about cross compilers or subsets. That is a totally different
topic. I guess you are arguing that PL/1 is still PL/1, and is not heavy because it's
old and not so full of features.
That is probably true in itself, but I still suspect that the requirements of a PL/1
compiler written in PL/1 are much higher than a PL/1 compiler written in assembler.
The DEC PDP-11 C compiler is not a subset, but is a pretty complete ANSI C. And it is not
a cross compiler. But the requirements of the compiler is high, and the code it produces
aren't that great.
The FORTRAN 77 compiler, as a comparison, produces much better code, and do lots of more
optimizations. Heck, even the DECUS C produces better code (that is, when it actually
manage to compile anything at all, it's a very retro K&R C implementation).
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic
trip
email: bqt at softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" -
B. Idol