[clang] [Clang][AArch64] Warn when calling streaming/non-streaming about vect… (PR #79842)

[Sander de Smalen via cfe-commits]

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@@ -3717,6 +3717,16 @@ def err_sme_definition_using_za_in_non_sme_target : Error<
   "function using ZA state requires 'sme'">;
 def err_sme_definition_using_zt0_in_non_sme2_target : Error<
   "function using ZT0 state requires 'sme2'">;
+def warn_sme_streaming_pass_return_vl_to_non_streaming : Warning<
+  "passing a VL-dependent argument to/from a function that has a different"
+  " streaming-mode, the streaming and non-streaming vector lengths may be"
+  " different">,
+  InGroup<AArch64SMEAttributes>;
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sdesmalen-arm wrote:

These warnings should be disabled by default, as the user may intentionally pass/return scalable vectors, knowing something about the target they're compiling for.

https://github.com/llvm/llvm-project/pull/79842