[llvm] [AArch64] Avoid using NEON FCVTXN in Streaming-SVE mode. (PR #91981)

[Paul Walker via llvm-commits]

https://github.com/paulwalker-arm commented:

Out of interest how bad is the code if you just disable the combine when NEON is not available.  I ask because given the IR the current code generation looks pretty poor so the combine doesn't seem all that useful in the long run.

https://github.com/llvm/llvm-project/pull/91981