From VMS to UNIX

[gwyn%brl-vld at sri-unix.UUCP]

From:      Doug Gwyn (VLD/VMB) <gwyn at brl-vld>

I think DVK is right about BLISS.  The only BLISS compilers I know
about are "globally optimizing".  The only C compiler I have
heard about that attempts this level of optimization was done for a
single CPU type (I forget which -- was presented two USENIX conferences
ago) and still is unlikely to beat BLISS as implemented by DEC.
DEC's VAX/VMS C compiler is presumably also highly optimizing.

As things now stand, those of us who really care about run-time code
efficiency resort to hand-optimizing our C source through careful
use of "local block" register variables and pointers, although this
would be better done by the compiler in many (not all) cases.  The
worst culprit is multiply-indexed arrays, speaking of which there
should be a reasonable way to write functions with variably-dimensioned
matrices as formal parameters!

On the other hand, BLISS is not widely available, and I was assured
by the developer that it would "never" fit on a PDP-11.  (Clearly a
BLISS compiler could do so, and I seem to recall a really old
BLISS-11 that did, but it was not the modern compiler.)

BLISS does have some neat features that C doesn't, such as anchored
variables.  Otherwise it is functionally equivalent to C, although
to my mind not as readable (I hate all those dots).  I think I would
agree that BLISS has a much better definition than anything I have
seen for C, and it does hang together well.  I doubt that I'll ever
use it, though!