With a recent-ish LLVM main (22.0.0) and current mainline (98906f9):
$ cat allno.config
CONFIG_ETHERNET=y
CONFIG_INET=y
CONFIG_MLX5_CORE=m
CONFIG_MLX5_CORE_EN=y
CONFIG_MODULES=y
CONFIG_NET=y
CONFIG_NET_VENDOR_MELLANOX=y
CONFIG_NETDEVICES=y
CONFIG_PCI=y
CONFIG_X86_KERNEL_IBT=y
$ make -skj"$(nproc)" ARCH=x86_64 KCONFIG_ALLCONFIG=1 LLVM=1 mrproper allnoconfig drivers/net/ethernet/mellanox/mlx5/core/mlx5_core.o
...
drivers/net/ethernet/mellanox/mlx5/core/mlx5_core.o: warning: objtool: mlx5e_mpwrq_max_log_rq_size() falls through to next function mlx5e_get_linear_rq_headroom()
This is not visible with LLVM 21.1.3.