Re: Whole program optimization and functions-only-called-once.

[Toon Moene <toon at moene dot org>]

Richard Guenther wrote:

> I think the underlying issue is
>
> phtask/41(-1) @0x7fd198c35100 availability:local 26416 time, 4268
> benefit 4541 size, 880 benefit 480 bytes stack usage reachable body
> local finalized inlinable
>  called by:
> phcall/33(-1) @0x7fd198c33a00 availability:local 8281 time, 972
> benefit 1351 size, 291 benefit 984 bytes stack usage reachable body
> local finalized inlinable
>  called by:
>
> that these are not called but still reachable (they should not be reachable
> anymore, instead the clones are now reachable).  I think there already is
> a bug about cloning not updating cgraph reachability and not reclaiming
> nodes after IPA transform application.

You don't happen to recall the bug number ?

The last time I did this sort of optimization was in 1992.

f2c (the Fortran-to-C compiler) gave me C equivalents of all Fortran 
code in the forecasting executable.

I spent a rainy Sunday afternoon to paste them into one giant source 
file, order them correctly (all called subroutines first) and then slap 
"static inline" on them.

Subsequently, I compiled the (30,000 line) C file with gcc -O3.  The 
resulting executable was about 10 % faster than the original (which was 
also compiled by f2c - g77 didn't exist at that time).

So my hopes on this optimization (when done right) are quite high :-)

--
Toon Moene - e-mail: toon@moene.org - phone: +31 346 214290
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