[clang] [CIR] Handle default arguments in ctors (PR #168649)

[Andy Kaylor via cfe-commits]

https://github.com/andykaylor updated https://github.com/llvm/llvm-project/pull/168649

>From 93aee4ffd29fd6ca0570e04f90e8009594faccb2 Mon Sep 17 00:00:00 2001
From: Andy Kaylor <akaylor at nvidia.com>
Date: Tue, 18 Nov 2025 18:33:51 -0800
Subject: [PATCH 1/2] [CIR] Handle default arguments in ctors

This adds the scalar expression visitor needed to handle default
arguments being passed to constructors.
---
 clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp |  4 ++++
 clang/test/CIR/CodeGen/defaultarg.cpp      | 22 ++++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp b/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp
index f777562ba6309..26e329250b6f3 100644
--- a/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp
@@ -711,6 +711,10 @@ class ScalarExprEmitter : public StmtVisitor<ScalarExprEmitter, mlir::Value> {
     return Visit(e->getSubExpr());
   }
 
+  mlir::Value VisitCXXDefaultArgExpr(CXXDefaultArgExpr *dae) {
+    CIRGenFunction::CXXDefaultArgExprScope Scope(cgf, dae);
+    return Visit(dae->getExpr());
+  }
   mlir::Value VisitCXXDefaultInitExpr(CXXDefaultInitExpr *die) {
     CIRGenFunction::CXXDefaultInitExprScope scope(cgf, die);
     return Visit(die->getExpr());
diff --git a/clang/test/CIR/CodeGen/defaultarg.cpp b/clang/test/CIR/CodeGen/defaultarg.cpp
index 807230bd003f5..29c929ccd7838 100644
--- a/clang/test/CIR/CodeGen/defaultarg.cpp
+++ b/clang/test/CIR/CodeGen/defaultarg.cpp
@@ -30,3 +30,25 @@ void foo() {
 // OGCG:   %[[TMP0:.*]] = alloca i32
 // OGCG:   store i32 42, ptr %[[TMP0]]
 // OGCG:   call void @_Z3barRKi(ptr {{.*}} %[[TMP0]])
+
+struct S
+{
+  S(int n = 2);
+};
+
+void test_ctor_defaultarg() {
+  S s;
+}
+
+// CIR: cir.func {{.*}} @_Z20test_ctor_defaultargv()
+// CIR:   %[[S:.*]] = cir.alloca !rec_S, !cir.ptr<!rec_S>, ["s", init]
+// CIR:   %[[TWO:.*]] = cir.const #cir.int<2> : !s32i
+// CIR:   cir.call @_ZN1SC1Ei(%[[S]], %[[TWO]]) : (!cir.ptr<!rec_S>, !s32i) -> ()
+
+// LLVM: define{{.*}} @_Z20test_ctor_defaultargv()
+// LLVM:   %[[S:.*]] = alloca %struct.S
+// LLVM:   call void @_ZN1SC1Ei(ptr %[[S]], i32 2)
+
+// OGCG: define{{.*}} @_Z20test_ctor_defaultargv()
+// OGCG:   %[[S:.*]] = alloca %struct.S
+// OGCG:   call void @_ZN1SC1Ei(ptr{{.*}} %[[S]], i32 {{.*}} 2)

>From 7636f83b1d6260710d7f4c81d667bc3e0d8d20b4 Mon Sep 17 00:00:00 2001
From: Andy Kaylor <akaylor at nvidia.com>
Date: Wed, 19 Nov 2025 10:59:49 -0800
Subject: [PATCH 2/2] Fix variable naming

---
 clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp b/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp
index 26e329250b6f3..382d9b2a06315 100644
--- a/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp
@@ -712,7 +712,7 @@ class ScalarExprEmitter : public StmtVisitor<ScalarExprEmitter, mlir::Value> {
   }
 
   mlir::Value VisitCXXDefaultArgExpr(CXXDefaultArgExpr *dae) {
-    CIRGenFunction::CXXDefaultArgExprScope Scope(cgf, dae);
+    CIRGenFunction::CXXDefaultArgExprScope scope(cgf, dae);
     return Visit(dae->getExpr());
   }
   mlir::Value VisitCXXDefaultInitExpr(CXXDefaultInitExpr *die) {