[CIR] Implement CXXDefaultInitExpr for Constants (llvm#164509)

Implement the CXXDefaultInitExpr for Constants

Author: AmrDeveloper

clang/lib/CIR/CodeGen/CIRGenExprConstant.cpp

@@ -1011,9 +1011,9 @@ class ConstExprEmitter
   }
 
   mlir::Attribute VisitCXXDefaultInitExpr(CXXDefaultInitExpr *die, QualType t) {
-    cgm.errorNYI(die->getBeginLoc(),
-                 "ConstExprEmitter::VisitCXXDefaultInitExpr");
-    return {};
+    // No need for a DefaultInitExprScope: we don't handle 'this' in a
+    // constant expression.
+    return Visit(die->getExpr(), t);
   }
 
   mlir::Attribute VisitExprWithCleanups(ExprWithCleanups *e, QualType t) {

clang/test/CIR/CodeGen/struct-init.cpp

@@ -15,6 +15,16 @@ S partial_init = { 1 };
 // LLVM: @partial_init = global %struct.S { i32 1, i32 0, i32 0 }
 // OGCG: @partial_init = global %struct.S { i32 1, i32 0, i32 0 }
 
+struct StructWithDefaultInit {
+  int a = 2;
+};
+
+StructWithDefaultInit swdi = {};
+
+// CIR: cir.global external @swdi = #cir.const_record<{#cir.int<2> : !s32i}> : !rec_StructWithDefaultInit
+// LLVM: @swdi = global %struct.StructWithDefaultInit { i32 2 }, align 4
+// OGCG: @swdi = global %struct.StructWithDefaultInit { i32 2 }, align 4
+
 void init() {
   S s1 = {1, 2, 3};
   S s2 = {4, 5};