[PATCH] D24956: [SelectionDAG] Add expansion and promotion of [US]MUL_LOHI

[Nicolai Hähnle via llvm-commits]

nhaehnle added inline comments.


> efriedma wrote in TargetLowering.h:147
> It doesn't look like None is actually used anywhere... did you mean to use it somehow?

I used it at some point to preserve the original behaviour. I'll remove it.

> efriedma wrote in TargetLowering.cpp:3156
> Why are you using ADDC+ADDE rather than just plain ADD?  It seems strange to split the operation, given that it might be legal.  (I might be missing something here, though.)

That's just how the code happened to evolve because AMDGPU (which is where this all started) doesn't have 64-bit additions, but it's a good point. I'm changing it to use additions in the larger type.

> efriedma wrote in SparcISelLowering.cpp:1696
> This FIXME doesn't make sense here; Promote is just the right thing to do here.

FIXME removed.

> efriedma wrote in X86ISelLowering.cpp:32532
> I'm confused; you're returning "Scalarize" for scalar types?

On X86 this only gets called for vector types. I'm adding an assertion to make that explicit.

https://reviews.llvm.org/D24956