I've only used C18 and SDCC (and I started the thread you mentioned :).
C18 is decent, but it either uses broken math (with no integer
promotion, which breaks the C standard) or has horrible, awful
optimization with integer promotion enabled (it will turn a simple BTFSS
into many instructions).

SDCC tends to do the right thing more often, though it does have a bug
or two every now and then. However, you can usually work around the bugs
(you can't really work around C18's stupid optimization, unless you turn
off IP, and then you have to change all of your code to deal with that
if it doesn't already, and hope that you never have to import some
generic C code that doesn't expect to be compiled with a broken
compiler). SDCC has pretty fast compilation times.

One thing I don't like about SDCC though is that it does a lot of
context saving in interrupts (I would like for it to be able to delay
the context saving until it is really needed, or have the option of
compiling interrupt code with a different register stack to avoid saving
anything). If you like fast interrupt code, you're going to have to do
some hacking. I had a project that needed some relatively fast interrupt
code, so what I did is declare a "naked" interrupt function (aka all
bets are off, no context saving at all; in fact it won't even add a
"return" for you). Then I used a few lines of assembler to do minimal
context saving, and call the main interrupt code. The main code is
basically a series of if statements and increments, tests, etc, and I
made sure they don't use any compiler registers when compiled (the fact
that SDCC doesn't do broken integer promotion helps here - everything
was 8 bits wide, so no temp registers were needed). When I need to call
code (during slow interrupts) that does a little more work, I do the
context saving myself.

I'm sure there's better stuff out there, but you can't really beat
SDCC's price. For my purposes, it works. Then again, I don't quite use
it for commercial purposes (yet).

-- 
Hector Martin (hector@marcansoft.com)
Public Key: http://www.marcansoft.com/marcan.asc

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