On 7/26/07, Basile STARYNKEVITCH <[EMAIL PROTECTED]> wrote:
Rohit Arul Raj wrote:
> Hi all,
>
> I have 3 functions- fun1, fun2, fun3 in the same source file and i
> want to enable one or any of the gcc optimization pass to code in fun2
> only,
>
> 1. Is it possible to implement this using function attributes or #pragms's?
I believe that currently, tuning optimisation levels at a function granularity
(or perhaps even smaller, like blocks) is
impossible in current GCC. I heard at the GCC summit (18th july 2007 at Ottawa)
that it would be a desirable feature,
but I am not sure that someone is actively working on it.
So currently, the answer seems to be no.
>
As of now,
a) I have added target dependent function attributes for all
optimization levels in the backend.
b) In function execute_pass_list() i am having a condition check for
those function attributes, if a valid optimization level is given
as a function attribute, the global variable optimize and
optimize_size are overridden for the current function. For other
functions, the global variables are restored to their initial values.
For a simple case- fun1, fun2, fun3, i gave function attribute O1 to
fun2, while the other 2 functions optimization was not enabled. The
only difference i found was that IPA passes were not run, other than
that the code was optimized for fun2.
I am yet to check how it affects other cases.
Is there any other better way of implementing this?
> 2. What will be its side-effects?
Apparently, one of the issues is that some optimising passes (or their
combination) rely on some global variable, so it
is not a trivial job to tune optimisations at the function level.
But I may be wrong on both points.
--
Basile STARYNKEVITCH http://starynkevitch.net/Basile/
email: basile<at>starynkevitch<dot>net | mobile: +33 6 8501 2359
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*** opinions {are only mine, sont seulement les miennes} ***
Regards,
Rohit
