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

[Sander de Smalen via llvm-commits]

sdesmalen-arm wrote:

> 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.

The output of disabling the combine when NEON is not available, are the SVE-NEXT lines in the test.

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