[clang] [CIR] Implement __builtin_return_address and __builtin_frame_address (PR #153698)

[Andy Kaylor via cfe-commits]

================
@@ -2210,6 +2210,67 @@ def CIR_CallOp : CIR_CallOpBase<"call", [NoRegionArguments]> {
   ];
 }
 
+//===----------------------------------------------------------------------===//
+// ReturnAddrOp and FrameAddrOp
+//===----------------------------------------------------------------------===//
+
+class CIR_FuncAddrBuiltinOp<string mnemonic> : CIR_Op<mnemonic, []> {
+  let arguments = (ins CIR_UInt32:$level);
+  let results = (outs CIR_VoidPtrType:$result);
+  let assemblyFormat = [{
+    `(` $level `)` attr-dict
+  }];
+}
+
+def CIR_ReturnAddrOp : CIR_FuncAddrBuiltinOp<"return_address"> {
+  let summary =
+      "The return address of the current function, or of one of its callers";
+
+  let description = [{
+    Represents call to builtin function ` __builtin_return_address` in CIR.
----------------
andykaylor wrote:

```suggestion
    Represents a call to builtin function ` __builtin_return_address` in CIR.
```

https://github.com/llvm/llvm-project/pull/153698