newbie building a scratch-built computer

[Brad Parker]

"Ensor" wrote:
>
>The last time I had a job as an assembly language programmer was 16 years 
>ago, and even then those types of jobs were damn thin on the ground (now 
>they're non-existant) - since every idiot these days seems to think "C" is 
>the way to go....which it isn't.... :-(

The last thing I want is 1600 posts to this list on a flame war about "c
versus asm", so *PLEASE* don't respond to this over and over,

but, as an anecdote,

I recently hand coded a PPC algorithm in assembler, and spend 3-4 days
working on it, got it all pretty and tight and when I benchmarked it,
the hand written code was *SLOWER* than the C code.

GCC is pretty good at generating fast code these days if - like any tool -
you learn how to use it.

Now I did hand-tune the c-code for a number of days, checking cycle
counts on a simulator and moving things around to force the compiler to
do things, did a lot of inline-ing and things like using constant array
indexes and explicit if's where possible.

So these days my feeling is that C is just a high level assembler, with
a expression optimizer on top.

don't get me wrong.  I use assemblers all the time, for lots of different
machines, but I was recently surprised  to be beaten by a machine.

I'll also note that this is a 32 bit machine.  My comments only really
apply to 32 bit machines with a reasonable pipeline and some amount of
branch prediction.

I've been able to do *much* better than the compiler writing assembler on
super-super-scaler cpu's like the TI DM642.  But trying to keep 6 ALU's
going at one time can make your head explode.

-brad