🚀 go-pugleaf

In article <MOSS.90Sep5193730@ibis.cs.umass.edu> moss@cs.umass.edu
(Eliot Moss) writes:

| Sometimes this tells a lot more about a *compiler* than it tells about
| hardware. My guess is that the 80x86 compilers may not be as good at some
| fancy optimizations, whereas the DEC C compiler is pretty good. If you want to
| compare the hardware alone, code in assembly (but that does not give a fair
| comparison if your programming will be in C). Another thing to do is to use
| more similar compilers, e.g., the GNU C compielr, which I believe is available
| for both of these machines/OSs. I also agree with the other respondent that it
| is not necessarily a very informative benchmark; be very careful in this kind
| of comparison! I would also not call a 3 MIP (or so) VAX "low-end"; one VAX
| instruction can do a lot more than one 80x86 instruction in many cases, and
| workstation I/O and memory systems are perhaps better designed than PC class
| boxes (and mainframes even better than that, etc.).

Two notes:  1) the MIPS assembler does backend optimizations -- if you
use GCC with it, you get some of the optimizations normally done with
the MIPS compiler suite;  2) If you are using GCC, I did a lot of
tuning and patching, so you probably want to start with my patches or
wait to 1.38.

The experience of tuning and hacking the 88k and MIPS ports for GCC
has showed me that there is a lot of stuff that can be done in the
machine dependent layer of the compiler that affects performance
drastically.  Sometimes changing one byte (such as in a constraint)
can mean quite a bit.  This means that you still have an apples vs.
oranges comparison if you compare GCC ports (though not as much of
one).  It depends on how much time & effort has been spent tuning
things for each port.  A young port of GCC will tend to be less
optimal than it could be.


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Michael Meissner	email: meissner@osf.org		phone: 617-621-8861
Open Software Foundation, 11 Cambridge Center, Cambridge, MA, 02142

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