[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 +3717,30 @@ 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_caller_pass_args_to_non_streaming : Warning<
+  "streaming caller passes a VL-dependent argument to non-streaming callee, "
+  "the streaming and non-streaming vector lengths may be different">,
+  InGroup<AArch64SMEAttributes>;
+def warn_sme_non_streaming_callee_returns_to_streaming : Warning<
+  "non-streaming callee returns a VL-dependent value to streaming caller, "
+  "the streaming and non-streaming vector lengths may be different">,
+  InGroup<AArch64SMEAttributes>;
+def warn_sme_non_streaming_caller_pass_args_to_streaming : Warning<
+  "non-streaming caller passes a VL-dependent argument to streaming callee, "
+  "the streaming and non-streaming vector lengths may be different">,
+  InGroup<AArch64SMEAttributes>;
+def warn_sme_non_streaming_caller_returns_to_streaming : Warning<
+  "non-streaming callee returns a VL-dependent value to streaming caller, "
+  "the streaming and non-streaming vector lengths may be different">,
+  InGroup<AArch64SMEAttributes>;
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sdesmalen-arm wrote:

nit: I think we can use a single message for this, e.g. `"passing a VL-dependent argument to/from a function that has a different streaming-mode, is undefined behaviour"`

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