In the past, -femit-templates was a bit of an obtuse implementation.

You had quite a few options:
- none    -> don't emit any templates
- all     -> force emit all templates, even ones that were discarded by the front-end / had problems instantiating but were gagged.
- private -> same as 'all', but emit them privately rather than weak for targets that didn't support.
- normal  -> emit (subjective to whether or not the backend infers that it is referenced) this symbol if the front-end tells us to.
- auto    -> either 'normal' or 'private' depending on if the target supported weak.

This was a bit hairy to work with, as any bug fixes around emission problems could have had a knock-on effect that breaks the other switches.  So for the sake of simplicity - I removed 'all' and 'auto' and kept just the three behaviours.  The default being 'normal' unless -femit-templates/-fno-emit-templates was used, then the compiler either emitted everything privately, or nothing at all.  The fact that this was kept around at all was because there were still some problems with the gcc backend removing functions from the compilation it deemed unreferenced and uneeded, but had their address taken nonetheless causing all sorts of undefined linker errors in certain edge cases.

In gcc-4.9, we now have a way to override gcc's symbol elimitation via cgraph(decl)->forced_by_abi.  Along with the front-end's new template emission behaviour and an -allinst switch to turn on the pre-2.064 release behaviour, this has given us another opportunity to change and clean-up -femit-templates.

This is the score:
- Default behaviour is the same as in D 2.064
- -femit-templates is mapped to -allinst, all special code removed from the glue.
- -fno-emit-templates still means that no instantiated templates will be emitted to object file.

With that, we no longer require any special-case analysis of the front-end codegen [¹][²][³]


So, no more hacks in the front-end, the ability to switch between pre-2.064 and 2.064 template instantiation behaviour, and having a peace of mind that the compiler will emit what it's told to emit.  You'd think it's all looking good, wouldn't you...  :o)


[1]: https://github.com/D-Programming-Language/dmd/pull/2723
[2]: https://github.com/D-Programming-GDC/GDC/blob/master/gcc/d/dfrontend/template.c#L5142
[3]: https://github.com/D-Programming-GDC/GDC/blob/master/gcc/d/dfrontend/template.c#L5171