[clang] [clang][SME] Rework streaming mode always_inline errors/warnings (PR #174608)

[Sander de Smalen via cfe-commits]

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@@ -1829,6 +1829,11 @@ class DeclContext {
     // refers to an enclosing template for hte purposes of [temp.friend]p9.
     LLVM_PREFERRED_TYPE(bool)
     uint64_t FriendConstraintRefersToEnclosingTemplate : 1;
+
+    // Indicates this function contains a non-(arm)-streaming safe expression.
+    // This can be directly, or transitively via always_inline calls.
+    LLVM_PREFERRED_TYPE(bool)
+    uint64_t BodyContainsNonStreamingSafeExpression : 1;
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sdesmalen-arm wrote:

I don't know how palatable it is to add this target-specific information to the AST. Maybe it's possible to keep a separate map in SemaARM and to add some target hook to `SemaBase` (from which SemaARM is derived), and call that instead of setting a field in `FunctionDeclBitfields` directly?

https://github.com/llvm/llvm-project/pull/174608