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

[Bruno Cardoso Lopes via cfe-commits]

================
@@ -1097,6 +1117,24 @@ mlir::LogicalResult CIRToLLVMCallOpLowering::matchAndRewrite(
                              getTypeConverter(), op.getCalleeAttr());
 }
 
+mlir::LogicalResult CIRToLLVMReturnAddrOpLowering::matchAndRewrite(
+    cir::ReturnAddrOp op, OpAdaptor adaptor,
+    mlir::ConversionPatternRewriter &rewriter) const {
+  auto llvmPtrTy = mlir::LLVM::LLVMPointerType::get(rewriter.getContext());
+  replaceOpWithCallLLVMIntrinsicOp(rewriter, op, "llvm.returnaddress",
----------------
bcardosolopes wrote:

The information coming from these builtins are likely useful in order to mark some function as unsafe for certain optimizations (e.g. where the return address or stack addressed in general might escape), they feel very different IMO than random shift vectors for ARM SVE. That said, you are right we don't use them right now, but I'd argue for keeping them because their behavior could be more intrusive than regular intrinsics.

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