[llvm] [SelectionDAG] Wire up -gen-sdnode-info TableGen backend (PR #125358)

[Sergei Barannikov via llvm-commits]

s-barannikov wrote:

> > > Have we ever verified normal (non-target) SDNodes using similar logics you put in SDNodeInfo::verifyNode?
> > 
> > 
> > This `verifySDNode` checks `BUILD_PAIR` and `BUILD_VECTOR`, and there are also some ad-hoc asserts in `SelectionDAG::getNode()`, [example](https://github.com/llvm/llvm-project/blob/b7c8271601461e02fb567d6cd175fe20e123d78a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp#L6282).
> 
> Right, but I'm curious whether we should call SDNodeInfo::verifyNode on non-target nodes too. Because I think there is no mechanism to prevent users from inserting chain / glue operands with the wrong order in non-target nodes.

`SDNodeInfo::verifyNode` needs the generated node descriptions to do the checks, and those are currently generated only for target-specific nodes. Generating descriptions for non-target nodes is left as a (distant) future work; there are several difficulties (mainly, various kinds of irregularities) that I don't have time to deal with right now.
For the time being, we could implement custom checks in C++ code for non-target nodes with chains and glues, there aren't too many of them.


https://github.com/llvm/llvm-project/pull/125358