[clang] [CIR] Upstream addressof builtin (PR #177860)

[Amr Hesham via cfe-commits]

https://github.com/AmrDeveloper created https://github.com/llvm/llvm-project/pull/177860

Upstream the addressof builtin

>From 20f2206809851cc57fd9b45764dfe25dc7e14dfb Mon Sep 17 00:00:00 2001
From: Amr Hesham <amr96 at programmer.net>
Date: Sun, 25 Jan 2026 16:37:06 +0100
Subject: [PATCH] [CIR] Upstream addressof builtin

---
 clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp |  1 +
 clang/test/CIR/CodeGen/address-of.cpp   | 28 +++++++++++++++++++++++++
 2 files changed, 29 insertions(+)
 create mode 100644 clang/test/CIR/CodeGen/address-of.cpp

diff --git a/clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp b/clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp
index 0e5a5b531df78..88d37d56fcd78 100644
--- a/clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp
@@ -1646,6 +1646,7 @@ RValue CIRGenFunction::emitBuiltinExpr(const GlobalDecl &gd, unsigned builtinID,
   case Builtin::BIaddressof:
   case Builtin::BI__addressof:
   case Builtin::BI__builtin_addressof:
+    return RValue::get(emitLValue(e->getArg(0)).getPointer());
   case Builtin::BI__builtin_function_start:
     return errorBuiltinNYI(*this, e, builtinID);
   case Builtin::BI__builtin_operator_new:
diff --git a/clang/test/CIR/CodeGen/address-of.cpp b/clang/test/CIR/CodeGen/address-of.cpp
new file mode 100644
index 0000000000000..3b7f710977066
--- /dev/null
+++ b/clang/test/CIR/CodeGen/address-of.cpp
@@ -0,0 +1,28 @@
+// RUN: %clang_cc1 -std=c++20 -triple x86_64-unknown-linux-gnu -Wno-unused-value -fclangir -emit-cir %s -o %t.cir
+// RUN: FileCheck --input-file=%t.cir %s -check-prefix=CIR
+// RUN: %clang_cc1 -std=c++20 -triple x86_64-unknown-linux-gnu -Wno-unused-value -fclangir -emit-llvm %s -o %t-cir.ll
+// RUN: FileCheck --input-file=%t-cir.ll %s -check-prefix=LLVM
+// RUN: %clang_cc1 -std=c++20 -triple x86_64-unknown-linux-gnu -Wno-unused-value -emit-llvm %s -o %t.ll
+// RUN: FileCheck --input-file=%t.ll %s -check-prefix=OGCG
+
+struct Container {
+  int x;
+  int y;
+};
+
+void builtin_address_of() {
+  Container a;
+  Container* b = __builtin_addressof(a);
+}
+
+// CIR: %[[A_ADDR:.*]] = cir.alloca !rec_Container, !cir.ptr<!rec_Container>, ["a"]
+// CIR: %[[B_ADDR:.*]] = cir.alloca !cir.ptr<!rec_Container>, !cir.ptr<!cir.ptr<!rec_Container>>, ["b", init]
+// CIR: cir.store {{.*}} %[[A_ADDR]], %[[B_ADDR]] : !cir.ptr<!rec_Container>, !cir.ptr<!cir.ptr<!rec_Container>>
+
+// LLVM: %[[A_ADDR:.*]] = alloca %struct.Container, i64 1, align 4
+// LLVM: %[[B_ADDR:.*]] = alloca ptr, i64 1, align 8
+// LLVM: store ptr %[[A_ADDR]], ptr %[[B_ADDR]], align 8
+
+// OGCG: %[[A_ADDR:.*]] = alloca %struct.Container, align 4
+// OGCG: %[[B_ADDR:.*]] = alloca ptr, align 8
+// OGCG: store ptr %[[A_ADDR]], ptr %[[B_ADDR]], align 8