Explain please flto=x and flto-partition=y options

Konstantin Vladimirov konstantin.vladimirov@gmail.com
Tue Jul 24 11:25:00 GMT 2012


Hi,

Please point me to documentation where relation between specifying:

flto=x

and

flto-partition=y

described completely over the domain of possible (x, y) pairs.

I experience troubles with deducing possible values and their effect
from source code of gcc, google isn't helpful too.

Now I am trying to solve one particular problem with inlining (lto
compilation) in private backend (core compiler is gcc 4.6.3).

In brief: there is some code A, containing functions a() and b().
Being compiled with lto, b() is inlined in a() as it supposed to be.
Now consider larger code B. B have no references to both a() and b(),
but if we compile A+B with lto, b() is no more inlined into a().

I suppose problem is in LTO partition -- in situation of more code,
partitioned part may contain some other functions b() refers to, so
b() now can not be inlined in the presence of inter-module references.
But I am not sure what options I can specify to control partition and
tune lto compilation to catch problem between options, not between
sources.

---
With best regards, Konstantin



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