[LLVMdev] Fw: Thinking about "whacky" backends

[David A. Greene]

Reid Kleckner <reid.kleckner at gmail.com> writes:

> An alternative is to introduce these features, but add a target
> lowering phase that strips them from the IR and replaces them with the
> target-dependent equivalent.

I like this approach a lot.

> The downside here is that it undermines the "single IR" LLVM approach.

LLVM has never had a single IR as long as I've worked on it.  It's
always had at least five:

- LLVM IR
- SCEV
- Selection DAG
- Schedule DAG
- Machine IR

This is good and appropriate.

                              -Dave