[clang] [CIR][X86] Implement lowering for `_AddressOfReturnAddress` builtin (PR #171974)

[Haocong Lu via cfe-commits]

https://github.com/Luhaocong updated https://github.com/llvm/llvm-project/pull/171974

>From 9772a1690ff6d40db9f1263b812f644b095d7e66 Mon Sep 17 00:00:00 2001
From: Haocong Lu <haocong.lu at witintech.com>
Date: Fri, 12 Dec 2025 13:55:59 +0800
Subject: [PATCH] [CIR][X86] Implement lowering for `_AddressOfReturnAddress`
 builtin

- Add new `CIR_AddrOfReturnAddrOp` and support lowering it to LLVMIR
- Add CIR CodeGen for `_AddressOfReturnAddress` X86 builtin
---
 clang/include/clang/CIR/Dialect/IR/CIROps.td  | 23 +++++++++++
 clang/lib/CIR/CodeGen/CIRGenBuiltinX86.cpp    |  7 +++-
 .../CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp |  9 +++++
 clang/test/CIR/CodeGen/ms-intrinsics.c        | 40 +++++++++++++++++++
 4 files changed, 78 insertions(+), 1 deletion(-)
 create mode 100644 clang/test/CIR/CodeGen/ms-intrinsics.c

diff --git a/clang/include/clang/CIR/Dialect/IR/CIROps.td b/clang/include/clang/CIR/Dialect/IR/CIROps.td
index 868b813458aae..256e60c41981e 100644
--- a/clang/include/clang/CIR/Dialect/IR/CIROps.td
+++ b/clang/include/clang/CIR/Dialect/IR/CIROps.td
@@ -3339,6 +3339,29 @@ def CIR_FrameAddrOp : CIR_FuncAddrBuiltinOp<"frame_address"> {
   }];
 }
 
+//===----------------------------------------------------------------------===//
+// AddrOfReturnAddrOp
+//===----------------------------------------------------------------------===//
+
+def CIR_AddrOfReturnAddrOp : CIR_Op<"address_of_return_address"> {
+  let summary = "The place stores the return address of the current function";
+
+  let description = [{
+    Represents a call to builtin function `_AddressOfReturnAddress` in CIR.
+    This builtin function returns a pointer to the place in the stack frame
+    where the return address of the current function is stored.
+
+    Examples:
+
+    ```mlir
+    %addr = address_of_return_address() : !cir.ptr<!cir.int<u, 8>>
+    ```
+  }];
+
+  let results = (outs CIR_PointerType:$result);
+  let assemblyFormat = "attr-dict `:` qualified(type($result))";
+}
+
 //===----------------------------------------------------------------------===//
 // StackSaveOp & StackRestoreOp
 //===----------------------------------------------------------------------===//
diff --git a/clang/lib/CIR/CodeGen/CIRGenBuiltinX86.cpp b/clang/lib/CIR/CodeGen/CIRGenBuiltinX86.cpp
index f9e1f75a51143..e876d59bf1677 100644
--- a/clang/lib/CIR/CodeGen/CIRGenBuiltinX86.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenBuiltinX86.cpp
@@ -1706,7 +1706,12 @@ CIRGenFunction::emitX86BuiltinExpr(unsigned builtinID, const CallExpr *expr) {
                                     cir::SyncScopeKind::SingleThread));
     return mlir::Value{};
   }
-  case X86::BI_AddressOfReturnAddress:
+  case X86::BI_AddressOfReturnAddress: {
+    mlir::Location loc = getLoc(expr->getExprLoc());
+    mlir::Value addr =
+        cir::AddrOfReturnAddrOp::create(builder, loc, allocaInt8PtrTy);
+    return builder.createCast(loc, cir::CastKind::bitcast, addr, voidPtrTy);
+  }
   case X86::BI__stosb:
   case X86::BI__ud2:
   case X86::BI__int2c:
diff --git a/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp b/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp
index 7d854997848aa..73f9e5390b886 100644
--- a/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp
+++ b/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp
@@ -1653,6 +1653,15 @@ mlir::LogicalResult CIRToLLVMFrameAddrOpLowering::matchAndRewrite(
   return mlir::success();
 }
 
+mlir::LogicalResult CIRToLLVMAddrOfReturnAddrOpLowering::matchAndRewrite(
+    cir::AddrOfReturnAddrOp op, OpAdaptor adaptor,
+    mlir::ConversionPatternRewriter &rewriter) const {
+  const mlir::Type llvmPtrTy = getTypeConverter()->convertType(op.getType());
+  replaceOpWithCallLLVMIntrinsicOp(rewriter, op, "llvm.addressofreturnaddress",
+                                   llvmPtrTy, adaptor.getOperands());
+  return mlir::success();
+}
+
 mlir::LogicalResult CIRToLLVMLoadOpLowering::matchAndRewrite(
     cir::LoadOp op, OpAdaptor adaptor,
     mlir::ConversionPatternRewriter &rewriter) const {
diff --git a/clang/test/CIR/CodeGen/ms-intrinsics.c b/clang/test/CIR/CodeGen/ms-intrinsics.c
new file mode 100644
index 0000000000000..fa6872c207c92
--- /dev/null
+++ b/clang/test/CIR/CodeGen/ms-intrinsics.c
@@ -0,0 +1,40 @@
+// RUN: %clang_cc1 -x c -ffreestanding -fms-extensions -fms-compatibility -fms-compatibility-version=17.00 \
+// RUN:   -triple x86_64-unknown-linux -Wno-implicit-function-declaration -fclangir -emit-cir -o %t.cir %s
+// RUN: FileCheck --check-prefix=CIR --input-file=%t.cir %s
+// RUN: %clang_cc1 -x c++ -ffreestanding -fms-extensions -fms-compatibility -fms-compatibility-version=17.00 \
+// RUN:   -triple x86_64-unknown-linux -Wno-implicit-function-declaration -fclangir -emit-cir -o %t.cir %s
+// RUN: FileCheck --check-prefix=CIR --input-file=%t.cir %s
+
+// RUN: %clang_cc1 -x c -ffreestanding -fms-extensions -fms-compatibility -fms-compatibility-version=17.00 \
+// RUN:   -triple x86_64-unknown-linux -Wno-implicit-function-declaration -fclangir -emit-llvm -o %t.ll %s
+// RUN: FileCheck --check-prefix=LLVM --input-file=%t.ll %s
+// RUN: %clang_cc1 -x c++ -ffreestanding -fms-extensions -fms-compatibility -fms-compatibility-version=17.00 \
+// RUN:   -triple x86_64-unknown-linux -Wno-implicit-function-declaration -fclangir -emit-llvm -o %t.ll %s
+// RUN: FileCheck --check-prefix=LLVM --input-file=%t.ll %s
+
+// RUN: %clang_cc1 -x c -ffreestanding -fms-extensions -fms-compatibility -fms-compatibility-version=17.00 \
+// RUN:   -triple x86_64-unknown-linux -emit-llvm -Wall -Werror %s -o - \
+// RUN:   | FileCheck %s -check-prefix=OGCG
+// RUN: %clang_cc1 -x c++ -ffreestanding -fms-extensions -fms-compatibility -fms-compatibility-version=17.00 \
+// RUN:   -triple x86_64-unknown-linux -emit-llvm -Wall -Werror %s -o - \
+// RUN:   | FileCheck %s -check-prefix=OGCG
+
+// This test mimics clang/test/CodeGen/ms-intrinsics.c, which eventually
+// CIR shall be able to support fully.
+
+void *_AddressOfReturnAddress(void);
+
+#if defined(__i386__) || defined(__x86_64__) || defined (__aarch64__)
+void *test_AddressOfReturnAddress(void) {
+  // CIR-LABEL: test_AddressOfReturnAddress
+  // CIR: %[[ADDR:.*]] = cir.address_of_return_address : !cir.ptr<!u8i>
+  // CIR: %{{.*}} = cir.cast bitcast %[[ADDR]] : !cir.ptr<!u8i> -> !cir.ptr<!void>
+
+  // LLVM-LABEL: test_AddressOfReturnAddress
+  // LLVM: call ptr @llvm.addressofreturnaddress.p0()
+
+  // OGCG-LABEL: test_AddressOfReturnAddress
+  // OGCG: call ptr @llvm.addressofreturnaddress.p0()
+  return _AddressOfReturnAddress();
+}
+#endif