[CIR][CIRGen][Builtin] Support __builtin_return_address (#1046)

test case is from [Traditional Clang CodeGen test
file](https://github.com/llvm/clangir/blob/723e78afb5ae4fbd000269a057410913ade3ef44/clang/test/CodeGen/2004-02-13-BuiltinFrameReturnAddress.c#L5)

Author: ghehg

clang/include/clang/CIR/Dialect/IR/CIROps.td

@@ -4125,6 +4125,37 @@ def MemChrOp : CIR_Op<"libc.memchr"> {
   let hasVerifier = 0;
 }
 
+//===----------------------------------------------------------------------===//
+// ReturnAddrOp
+//===----------------------------------------------------------------------===//
+
+def ReturnAddrOp : CIR_Op<"return_address"> {
+  let arguments = (ins UInt32:$level);
+  let summary = "The return address of the current function, or of one of its callers";
+  let results = (outs Res<VoidPtr, "">:$result);
+
+  let description = [{
+    Represents call to builtin function ` __builtin_return_address` in CIR. 
+    This builtin function returns the return address of the current function, 
+    or of one of its callers. 
+    The `level` argument is number of frames to scan up the call stack.
+    For instance, value of 0 yields the return address of the current function, 
+    value of 1 yields the return address of the caller of the current function, 
+    and so forth. 
+
+    Examples:
+
+    ```mlir
+    %p = return_address(%level) -> !cir.ptr<!void>
+    ```
+  }];
+
+  let assemblyFormat = [{
+    `(` $level `)` attr-dict
+  }];
+  let hasVerifier = 0;
+}
+
 //===----------------------------------------------------------------------===//
 // StdFindOp
 //===----------------------------------------------------------------------===//

clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp

@@ -1510,8 +1510,14 @@ RValue CIRGenFunction::buildBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
     llvm_unreachable("BI__builtin_wmemcmp NYI");
   case Builtin::BI__builtin_dwarf_cfa:
     llvm_unreachable("BI__builtin_dwarf_cfa NYI");
-  case Builtin::BI__builtin_return_address:
-    llvm_unreachable("BI__builtin_return_address NYI");
+  case Builtin::BI__builtin_return_address: {
+    mlir::Location loc = getLoc(E->getExprLoc());
+    mlir::Attribute levelAttr = ConstantEmitter(*this).emitAbstract(
+        E->getArg(0), E->getArg(0)->getType());
+    int64_t level = mlir::cast<mlir::cir::IntAttr>(levelAttr).getSInt();
+    return RValue::get(builder.create<mlir::cir::ReturnAddrOp>(
+        loc, builder.getUInt32(level, loc)));
+  }
   case Builtin::BI_ReturnAddress:
     llvm_unreachable("BI_ReturnAddress NYI");
   case Builtin::BI__builtin_frame_address:

clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp

@@ -4115,6 +4115,21 @@ class CIRCmpThreeWayOpLowering
   }
 };
 
+class CIRReturnAddrOpLowering
+    : public mlir::OpConversionPattern<mlir::cir::ReturnAddrOp> {
+public:
+  using OpConversionPattern<mlir::cir::ReturnAddrOp>::OpConversionPattern;
+
+  mlir::LogicalResult
+  matchAndRewrite(mlir::cir::ReturnAddrOp op, OpAdaptor adaptor,
+                  mlir::ConversionPatternRewriter &rewriter) const override {
+    auto llvmPtrTy = mlir::LLVM::LLVMPointerType::get(rewriter.getContext());
+    replaceOpWithCallLLVMIntrinsicOp(rewriter, op, "llvm.returnaddress",
+                                     llvmPtrTy, adaptor.getOperands());
+    return mlir::success();
+  }
+};
+
 class CIRClearCacheOpLowering
     : public mlir::OpConversionPattern<mlir::cir::ClearCacheOp> {
 public:
@@ -4370,9 +4385,16 @@ void populateCIRToLLVMConversionPatterns(
       CIRVectorShuffleVecLowering, CIRStackSaveLowering, CIRUnreachableLowering,
       CIRTrapLowering, CIRInlineAsmOpLowering, CIRSetBitfieldLowering,
       CIRGetBitfieldLowering, CIRPrefetchLowering, CIRObjSizeOpLowering,
+      CIRIsConstantOpLowering, CIRCmpThreeWayOpLowering, CIRMemCpyOpLowering,
+      CIRFAbsOpLowering, CIRExpectOpLowering, CIRVTableAddrPointOpLowering,
+      CIRVectorCreateLowering, CIRVectorCmpOpLowering, CIRVectorSplatLowering,
+      CIRVectorTernaryLowering, CIRVectorShuffleIntsLowering,
+      CIRVectorShuffleVecLowering, CIRStackSaveLowering, CIRUnreachableLowering,
+      CIRTrapLowering, CIRInlineAsmOpLowering, CIRSetBitfieldLowering,
+      CIRGetBitfieldLowering, CIRPrefetchLowering, CIRObjSizeOpLowering,
       CIRIsConstantOpLowering, CIRCmpThreeWayOpLowering,
-      CIRClearCacheOpLowering, CIREhTypeIdOpLowering, CIRCatchParamOpLowering,
-      CIRResumeOpLowering, CIRAllocExceptionOpLowering,
+      CIRReturnAddrOpLowering, CIRClearCacheOpLowering, CIREhTypeIdOpLowering,
+      CIRCatchParamOpLowering, CIRResumeOpLowering, CIRAllocExceptionOpLowering,
       CIRFreeExceptionOpLowering, CIRThrowOpLowering, CIRIntrinsicCallLowering,
       CIRAssumeLowering, CIRAssumeAlignedLowering, CIRAssumeSepStorageLowering,
       CIRBaseClassAddrOpLowering, CIRDerivedClassAddrOpLowering,

clang/test/CIR/CodeGen/builtins.cpp

@@ -75,3 +75,14 @@ extern "C" char* test_memchr(const char arg[32]) {
   // LLVM: [[RET:%.*]] = load ptr, ptr [[RET_P]], align 8
   // LLVM: ret ptr [[RET]]
 }
+
+extern "C" void *test_return_address(void) {
+  return __builtin_return_address(1);
+
+  // CIR-LABEL: test_return_address
+  // [[ARG:%.*]] = cir.const #cir.int<1> : !u32i
+  // {{%.*}} = cir.return_address([[ARG]])
+
+  // LLVM-LABEL: @test_return_address
+  // LLVM: {{%.*}} = call ptr @llvm.returnaddress(i32 1)
+}

clang/test/CIR/IR/builtins.cir

@@ -0,0 +1,14 @@
+// RUN: cir-opt %s | cir-opt | FileCheck %s
+!u32i = !cir.int<u, 32>
+
+module  {
+  cir.func @test1() {
+    %0 = cir.const #cir.int<1> : !u32i
+    %1 = cir.return_address(%0)
+    cir.return
+  }
+  // CHECK:  cir.func @test1()
+  // CHECK:  %0 = cir.const #cir.int<1> : !u32i
+  // CHECK:  %1 = cir.return_address(%0)
+  // CHECK: cir.return
+}