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

[Kenzo Tjandra 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;
----------------
ketjandr wrote:

Ahh I get what you're saying now... so if we have instead
```
[[musttail]]
return outer_fn(({
  inner_fn();
}));
```
`MustTailCall` still remains preserved (pointing to `outer_fn`) as we recurse inside the stmt-expr, as opposed to
```
[[musttail]]
return outer_fn(({
  [[always_inline]]
  inner_fn();
}));
```
which will clobber `MustTailCall` since `always_inline` saves it as `nullptr`. So the intended behavior should be as if `always_inline` isn't there. Am I understanding this correctly?

And a follow-up would be - do you think this should apply to all the other statement attributes then?

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