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

[Jonathan Wakely]

On 24 July 2012 12:25, Konstantin Vladimirov wrote:
> 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.

Did you look in the manual?

http://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#index-flto-873