[OpenBIOS] compiler speed

[Segher Boessenkool]

Klaus Seegebarth wrote:
> 
> Stefan Reinauer wrote:
> > 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.
> >
> >[snip...snip]
> >
> > Comments?
> 
> 22% difference is "like nothing" for me. A factor of 10 is "a lot" for me.

1% speedup is a nice optimization, and 2% slowdown is a serious performance
regression.

22% slowdown is just awful.  Try compiling with -O2 or -Os (not -O3), and
playing with the several optimization switches (esp. some of the jump
optimization passes seem to cause more trouble than help).

I'll try to find out what's going on here exactly.


Segher


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