[clang] [CIR] Unblock simple C++ structure support (PR #138368)

[Andy Kaylor via cfe-commits]

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@@ -365,10 +365,15 @@ mlir::Attribute ConstantEmitter::tryEmitPrivateForVarInit(const VarDecl &d) {
   if (!d.hasLocalStorage()) {
     QualType ty = cgm.getASTContext().getBaseElementType(d.getType());
     if (ty->isRecordType())
-      if (d.getInit() && isa<CXXConstructExpr>(d.getInit())) {
-        cgm.errorNYI(d.getInit()->getBeginLoc(),
-                     "tryEmitPrivateForVarInit CXXConstructExpr");
-        return {};
+      if (const CXXConstructExpr *e =
+              dyn_cast_or_null<CXXConstructExpr>(d.getInit())) {
+        const CXXConstructorDecl *cd = e->getConstructor();
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andykaylor wrote:

I see. If I add `-std=c++14` to my compile line, that gets the elidable constructor in the AST, and then `-fno-elide-constructors` get us to emit CIR for it but not here. That's handled in `emitCXXConstructExpr` (which has not been upstreamed yet). I guess the `cd->isTrivial() && cd->isDefaultConstructor()` check prevents us from doing anything with it here.

https://github.com/llvm/llvm-project/pull/138368