On 23 Apr 2007, at 20:43, Diego Novillo wrote:
[EMAIL PROTECTED] wrote on 04/23/07 14:37:
Currently, the -On flags set/unset 60 flags, which yields 2^60 conbinations.
If you also kind the passes not controlled by a flag, but decided upon
depending on the optimization level, that adds another, virtual flag
(i.e. using -O1, -O2, -O3 or -Os as base setting).
No, that's not what I want. I want a static recipe. I do *not* want
-Ox to do this search every time.
I'm not saying you need to do this every time you install GCC. I'm
saying trying out 2^60 combinations (even offline) is totally
unfeasible.
It goes like this: Somebody does a study over a set of applications that
represent certain usage patterns (say, FP and INT just to mention the
two more common classes of apps). The slow search is done offline and
after a few months, we get the results in the form of a table that says
for each class and for each -Ox what set of passes to execute and in
what order they should be executed.
Not to say that the current sequencing and repetition are worthless, but
I think they could be improved in a quasi systematic way using this
process (which is slow and painful, I know).
Exactly my idea.
My work is actually concentrating on building a framework to do
exactly that: give a set of recipes for -On flags which allow a
choice, and which are determined by trading off compilation time,
execution time and code size.
Right. This is what I want.
I won't be at the GCC summit in Canada (I'm in San Diego then
presenting some other work), but I'll make sure to announce our work
when it's finished...
Excellent. Looking forward to those results.
Cool!
--
Statistics are like a bikini. What they reveal is suggestive, but what
they conceal is vital (Aaron Levenstein)
Kenneth Hoste
ELIS - Ghent University
[EMAIL PROTECTED]
http://www.elis.ugent.be/~kehoste
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