> On Tue, May 8, 2018 at 8:14 AM, Jan Hubicka <hubi...@ucw.cz> wrote: > > Hi, > > with lto, incremental linking can be meaninfuly done in three ways: > > 1) read LTO file and produce non-LTO .o file > > this is current behaviour of gcc -r or ld -r with plugin > > 2) read LTO files and merge section for later LTO > > this is current behaviour of ld -r w/o plugin > > 3) read LTO files into the compiler, link them and produce > > incrementaly linked LTO object. > > > > 3 makes most sense and I am maing it new default for gcc -r. For testing > > purposes > > and perhaps in order to have tool to turn LTO object into real object, we > > want > > to have 1) available as well. GCC currently have -flinker-output option > > that > > decides between modes that is decided by linker plugin and can be > > overwritten > > by user (I have forgot to document this). > > > > I am targeting for -flinker-output=rel to be incremental linking into LTO > > and adding -flinker-output=nolto-rel for 1). > > > > The main limitation of 2 and 3 is that you can not link LTO and non-LTO > > object files theger. For 2 HJ's binutils patchset has support and I think > > it can be extended to handle 3 as well. But with default binutils we want > > to warn users. This patch implements the warning (and prevents linker > > plugin > > to add redundat linker-ouptut options. > > > My users/hjl/lto-mixed/master branch is quite flexible. I can extend > it if needed.
I think once the main patchset settles down we could add a way to communicate to lto-plugin if combined lto+non-lto .o files are supported by linker and sillence the warning. Honza > > -- > H.J.
