[llvm] [X86] combineConcatVectorOps - add concatenation handling for BITCAST nodes (PR #133913)

[Hans Wennborg via llvm-commits]

zmodem wrote:

I've uploaded an unreduced repro here: https://crbug.com/409794994#comment4 I'll see if I can turn that into something smaller..

https://github.com/llvm/llvm-project/pull/133913