Use TCC backend for LDC?

[Temtaime]

Hi !
http://bellard.org/tcc/
TCC is a great C compiler with very fast compilation speed.
What if we could use its backend in debug builds instead of llvm ?
I think we could beat dmd.

[dnadlinger]

Sorry, this is pretty much off topic/out of the scope of LDC. Quite simply, TCC is missing the L in the name. ;) Of course, people are always welcome to try and improve the compilation speed of D. If such a new project would still use the DMD frontend, we could even integrate it into LDC afterwards.

[redstar]

As a sidenote, adding a complete new backend is a considerable effort. IMHO this effort is better spent profiling LDC/LLVM.

[JohanEngelen]

There is some talk in the Rust issue tracker about try to emit code such that FastISel of LLVM can be used. Supposedly, that is much faster in generating unoptimizated code... rust-lang/rust#26600 I really do not know if it is worth the effort.

[smolt]

Doesn't -O0 use FastISel where it can already? I'll have to read the reference.

[JohanEngelen]

We don't yet use FastISel from as far as I could tell from LDC source, because I think we have to explicitly enable it. I enabled it, but it did not change compile times much. I think we fall back to the other DAG... instruction selector very quickly, as many of LDC's constructs are not supported by FastISel. Haven't really tested much though.