This patch simplified IR generation for builtin_btf_type_id().
For builtin_btf_type_id(obj, flag), previously IR builtin
if (obj is a lvalue) llvm.bpf.btf.type.id(obj.ptr, 1, flag) !type else llvm.bpf.btf.type.id(obj, 0, flag) !type
The purpose of the 2nd argument is to differentiate
__builtin_btf_type_id(obj, flag) where obj is a lvalue
Note that obj or obj.ptr is never used by the backend
and the obj argument is only used to derive the type.
This code sequence is subject to potential llvm CSE when
- obj is the same .e.g., nullptr
- flag is the same
- metadata type is different, e.g., typedef of struct "s" and strust "s".
In the above, we don't want CSE since their metadata is different.
This patch change IR builtin to
llvm.bpf.btf.type.id(seq_num, flag) !type
and seq_num is always increasing. This will prevent potential
Also report an error if the type name is empty for
remote relocation since remote relocation needs non-empty
type name to do relocation against vmlinux.