[OpenBIOS] compiler speed

[Stefan Reinauer]

Hi,

I played a bit with different gcc versions on Alpha and I
noticed that when executing the FIB test from
http://home.iae.nl/users/mhx/fib.html in paflof, results
are _a lot_ slower with gcc 3.1.1 than with 2.96 (SuSE 7.1
Alpha release) Not only is the 3.1.1 binary about 20%
bigger,
it also 22% slower.

The test:
HEX
: FIB ( x -- y ) RECURSIVE
        DUP 2 > IF DUP  1- RECURSE
                SWAP 2- RECURSE +  EXIT
        THEN    
        DROP 1 ;

28 FIB
BYE     

The results:
gcc 2.96 binary
        real    1m55.642s
        user    1m55.479s
        sys     0m0.014s

gcc 3.1.1 binary
        real    2m21.763s
        user    2m21.533s
        sys     0m0.027s

Where does this come from? Is the code generated by gcc 3.x really that
slow, compared to 2.96? Do we make some assumptions that might cause
this? (How badly do gotos break code flow analysis for example?)

What can we do against this? Having more prim words will speed up the
whole thing, but probably not really make it easier for the compiler to
optimize.

Comments?

  Stefan..
-- 
The x86 isn't all that complex - it just doesn't make a lot of
sense.          -- Mike Johnson, Leader of 80x86 Design at AMD
	                          Microprocessor Report (1994)
-
To unsubscribe: send mail to majordomo at freiburg.linux.de
with 'unsubscribe openbios' in the body of the message
http://www.freiburg.linux.de/OpenBIOS/ - free your system..