[clang] [clang] Implement `__is_layout_compatible` (PR #81506)

[via cfe-commits]

================
@@ -14040,6 +14040,8 @@ class Sema final {
   bool SemaValueIsRunOfOnes(CallExpr *TheCall, unsigned ArgNum);
 
 public:
+  bool SemaIsLayoutCompatible(QualType T1, QualType T2);
----------------
cor3ntin wrote:

Agreed, this should be renamed IsLayoutCompatible (and be const)

https://github.com/llvm/llvm-project/pull/81506