[llvm] [AArch64][SME]Check streaming mode when using SME2 instruction in fra… (PR #109680)

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

aarch64_pstate_sm_body is locally streaming, where we're not in streaming mode at entry, but the prologue switches into streaming mode.  aarch64_pstate_sm_compatible is streaming-compatible: at the entry point, we don't know whether we're in streaming mode, so we can only use the subset of instructions that are legal inside and outside streaming mode.

https://github.com/llvm/llvm-project/pull/109680