[CIR] Backport GenericSelectionExpr for AggregateExpr (#1947)

Backporting support the GenericSelectionExpr for AggregateExpr from
upstream

Author: AmrDeveloper

clang/lib/CIR/CodeGen/CIRGenExpr.cpp

@@ -2671,6 +2671,8 @@ LValue CIRGenFunction::emitLValue(const Expr *E) {
   }
   case Expr::ParenExprClass:
     return emitLValue(cast<ParenExpr>(E)->getSubExpr());
+  case Expr::GenericSelectionExprClass:
+    return emitLValue(cast<GenericSelectionExpr>(E)->getResultExpr());
   case Expr::DeclRefExprClass:
     return emitDeclRefLValue(cast<DeclRefExpr>(E));
   case Expr::UnaryOperatorClass:

clang/lib/CIR/CodeGen/CIRGenExprAgg.cpp

@@ -179,7 +179,7 @@ class AggExprEmitter : public StmtVisitor<AggExprEmitter> {
   }
   void VisitParenExpr(ParenExpr *PE) { Visit(PE->getSubExpr()); }
   void VisitGenericSelectionExpr(GenericSelectionExpr *GE) {
-    llvm_unreachable("NYI");
+    Visit(GE->getResultExpr());
   }
   void VisitCoawaitExpr(CoawaitExpr *E) {
     CGF.emitCoawaitExpr(*E, Dest, IsResultUnused);

clang/test/CIR/CodeGen/struct.cpp

@@ -196,6 +196,19 @@ void designated_init_update_expr() {
 // CHECK: cir.store{{.*}} %[[CONST_1]], %[[ELEM_0_PTR]] : !s32i, !cir.ptr<!s32i>
 // CHECK: %[[ELEM_1_PTR:.*]] = cir.get_member %[[C_ADDR]][1] {name = "b"} : !cir.ptr<!rec_CompleteS> -> !cir.ptr<!s8i>
 
+void generic_selection() {
+  CompleteS a;
+  CompleteS b;
+  int c;
+  CompleteS d = _Generic(c, int : a, default: b);
+}
+
+// CHECK: %[[A_ADDR:.*]] = cir.alloca !rec_CompleteS, !cir.ptr<!rec_CompleteS>, ["a"]
+// CHECK: %[[B_ADDR:.*]] = cir.alloca !rec_CompleteS, !cir.ptr<!rec_CompleteS>, ["b"]
+// CHECK: %[[C_ADDR:.*]] = cir.alloca !s32i, !cir.ptr<!s32i>, ["c"]
+// CHECK: %[[D_ADDR:.*]] = cir.alloca !rec_CompleteS, !cir.ptr<!rec_CompleteS>, ["d", init]
+// CHECK: cir.copy %[[A_ADDR]] to %[[D_ADDR]] : !cir.ptr<!rec_CompleteS>
+
 void choose_expr() {
   CompleteS a;
   CompleteS b;
@@ -206,4 +219,4 @@ void choose_expr() {
 // CHECK:   %[[A_ADDR:.*]] = cir.alloca !rec_CompleteS, !cir.ptr<!rec_CompleteS>, ["a"]
 // CHECK:   %[[B_ADDR:.*]] = cir.alloca !rec_CompleteS, !cir.ptr<!rec_CompleteS>, ["b"]
 // CHECK:   %[[C_ADDR:.*]] = cir.alloca !rec_CompleteS, !cir.ptr<!rec_CompleteS>, ["c", init]
-// CHECK:   cir.copy %[[A_ADDR]] to %[[C_ADDR]] : !cir.ptr<!rec_CompleteS>
+// CHECK:   cir.copy %[[A_ADDR]] to %[[C_ADDR]] : !cir.ptr<!rec_CompleteS>