[llvm] [GlobalISel] Diagnose inline assembly constraint lowering errors (PR #135782)

[Pierre van Houtryve via llvm-commits]

Pierre-vh wrote:

> > Until we have some form of error recovery testing will be difficult because the compiler crashes on failure
> 
> It certainly should not crash

I just realized it doesn't have to crash, I can just enable the fallback path.
If I recover here, it "hides" the lowering failure away and we can't use the fallback path. I think recovery needs to be dependent on whether the fallback path is used or not, would that make sense?

And for recovery, I'm thinking of just using `buildUndef` on all dest registers. The inputs won't be handled though.


https://github.com/llvm/llvm-project/pull/135782