Herbert Graf <mailinglist3 <at> farcite.net> writes:

> On Sat, 2007-03-10 at 11:43 -0800, Don French wrote:
> > I see a lot of posts on this list that indicate that people are programming
in Assembly.  So, I wonder why. 
> Except for really tight timing situations, why not use C, which is one heck of
a lot easier to write, read,
> maintain, etc.?  And the optimizing compilers probably do at least as good a
job of saving bytes as most
> people can do by writing in Assembly.  So, what is the point? 
> 
> Well, main reasons I can see are:
> 
> - person doesn't know C (there are alot out there that don't)

That is a reason I do not agree with. I don't think that one can even get hired
for an embedded job without knowing C. C is the common denominator of
programming, especially low level, and has been for 20 years. Not knowing C is
about the same as going out of fashion whenever an architecture is retired. That
happens every six months or so now.

> - established ASM codebase - alot of people have been using ASM for a
> LONG time, and have a codebase that covers many things, why change to C
> if you already have most of the code written in ASM?

Because most of the valid reasons to use the old codebase were a lot of time
spent on optimization and cleaning up things. Because C has a math package built
in (well almost, with -lm) most of the old codebase that was
calculations-related can be duplicated in 5 seconds, the time to compile an
expression. And peripherals have changed enough that old code for peripherals
makes little sense imho. I see it that way while cleaning things in my computer,
things which are 10+ years old. My code was valid then, and it worked well, but
today it's just two more lines of C buried in the rest of what I am doing, and
it's likely faster than the way I coded it then. Compilers are written by very
clever people.

> - PIC projects are often small enough not to get many benefits from an
> HLL - for example a recent project I did was a "flickering candle", it's
> about 20 lines of ASM, hardly worth going to C

What happens if you have to add a USB interface in 2 weeks ? Or port it to
something else ? C would have used about 5 lines of code for that. Would it 'not
have been worth it' ? Try to think how long it took you to make the program
work. How long would it have taken in C ? 

Statistics say that American programmers produce about 50 lines of 'good' code
per day (including debug time). So your asm program should have taken almost
half a day, and the C program a tenth of a day. Afaik, the rule of thumb is to
use the highest level programming language available for the task.

> - compiler bugs - every compiler has bugs, and debugging compiler bugs
> can get very frustrating.

Yes, but so does everything else. Including one's own code. Assembly requires
5-10 times more source statements to achieve what C achieves. The programmer's
error rate is proportional to the number of lines of code he writes, not to the
language used.
 
> I still at least get an idea for how the ASM works for a given platform,
> that way when you hit a compiler bug (and you will) you'll be prepared
> to sift through the ASM listing to figure out what's going on.

Every man should know his compiler's output ;-)

Peter P.


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