On 29 June 2017 at 00:50, Mike via D.gnu <d.gnu@puremagic.com> wrote: > On Wednesday, 28 June 2017 at 22:17:09 UTC, Iain Buclaw wrote: >> If that is the case, you should definitely compile with -fwhole-program. >> I suspect that may cut down your compilation time by half or even more. > > > If I only import __entrypoint.d and pass the rest of the runtime files on > the command line and compile with -fwhole-program, it compiles in 5s, but I > only get an 8byte binary. I suspect this is due to the error above about > __entrypoint. That is, if there's no entry point, the whole program gets > garbage collected. > > I think you might be on to something here though. >
Yes, it seems like there's a more than a few hundred functions being emitted, and as they are all considered externally visible, none can be removed during the optimization pass. If they are all considered static (in the C sense), then unused and inlined functions can be removed immediately, giving the backend less work. I think the only caveat with using -fwhole-program is that C main must be present in the compilation, otherwise as you've noted, everything gets removed as unused code. Regards, Iain.
