On Thu, 6 Mar 2014, Jan Hubicka wrote: > > On Tue, 4 Mar 2014, Jan Hubicka wrote: > > > > > > > > > > The following patch addresses the common (?) issue of people > > > > omitting -flto from the linker command-line which gets more > > > > severe with GCC 4.9 where slim LTO objects are emitted by > > > > default. The patch simply _always_ arranges for the linker > > > > plugin to be used, so if there are any (slim) LTO objects > > > > on the link LTO will be done on them. Similarly the > > > > non-linker-plugin path in collect2 is adjusted. > > > > > > > > You can still disable this by specifying -fno-lto on the > > > > linker command-line. > > > > > > > > One side-effect of enabling the linker-plugin by default > > > > (for HAVE_LTO_PLUGIN == 2) is that collect2 will then > > > > use the configured plugin ld rather than the default ld. > > > > Not sure if that is desired. > > > > > > > > Comments? > > > > > > I like it; it was on my TODO list, but I was only worried about > > > --with-plugin-ld and did not find time, yet, to look into the > > > consequences. > > > These days, I do not think we need to worry much aboud --with-plugin-ld. > > > > Yeah, I think we should eventually remove that capability. > > > > Now as of the two patches (compute a default link-time optimization > > level and this patch, make considering LTO at link-time the default), > > they only make sense together (at least the default opt level at > > link-time doesn't improve real-world situations without also considering > > all links to be possibly -flto). > > > > So the question remains if we want to have both patches at this > > stage or if we want to wait with them for 4.10 (we do have the > > user-visible change of slim-lto objects by default with 4.9 > > already). > > I think it makes things easier, so I would like to see this in 4.9
Ok. I'll push this to trunk now and then prepare a documentation update for LTO opts handling (as promised some time ago ...). If any issues show up with these two patches then we'll revert and revisit this for 4.10. Thanks, Richard.
