Effect of -mtune=* on x86 or x86-64 systems?

[Michael Meissner]

On Wed, Jan 07, 2009 at 10:21:28AM -0500, Wirawan Purwanto wrote:
> Hi Michael,
> 
> Thanks for the answer. I would  like to know if someone has investigated 
> this issue for some benchmark or real-world cases. Is there any 
> write-up/report/paper on this thing?

You might want to look at milepost GCC:
http://www.fursin.net/research_iter.html
http://www.fursin.net/papers/fmtp2008.pdf
http://cccpf.sourceforge.net/

I suspect many people have done tests, but often times not published the
results.  For example, when I worked for AMD, I sometimes did SPEC runs with
-mtune=generic, -mtune=athlon, -mtune=barcelona, or -mtune=core2 to see how the
tunings affected the real hardware.  I recall that there were a few benchmarks
which saw noticible differences (how integer to fp conversions was one that I
looked at for a bit).

-- 
Michael Meissner, IBM
4 Technology Place Drive, MS 2203A, Westford, MA, 01886, USA
meissner@linux.vnet.ibm.com