[clang] [Clang] Diagnose conflict between always_inline/noinline attributes (PR #215173)

[Erich Keane via cfe-commits]

================
@@ -779,10 +779,10 @@ void CodeGenFunction::EmitLabelStmt(const LabelStmt &S) {
 }
 
 void CodeGenFunction::EmitAttributedStmt(const AttributedStmt &S) {
-  bool nomerge = false;
-  bool noinline = false;
-  bool alwaysinline = false;
-  bool noconvergent = false;
+  bool nomerge = InNoMergeAttributedStmt;
+  bool noinline = InNoInlineAttributedStmt;
+  bool alwaysinline = InAlwaysInlineAttributedStmt;
+  bool noconvergent = InNoConvergentAttributedStmt;
   StringRef amdgpuAVMode;
----------------
erichkeane wrote:

Uh, why shouldn't musstail propagate inwards?  Why should:
```
[[musttail]] {
   some_call;
}
```
and
```
[[musttail]] {
   [[always_inline]]
   some_call;
}
```

Have DIFFERENT musttail behaviors?  EXISTING behavior is that it will propagate to the inner statement, unless we have an attributedstmt (possibly/likely unrelated), so it shouldn't 'change' it.

https://github.com/llvm/llvm-project/pull/215173