btf: change encoding of forward-declared enums [PR111735]

The BTF specification does not formally define a representation for
forward-declared enum types such as:

  enum Foo;

Forward-declarations for struct and union types are represented by
BTF_KIND_FWD, which has a 1-bit flag distinguishing the two.

The de-facto standard format used by other tools like clang and pahole
is to represent forward-declared enums as BTF_KIND_ENUM with vlen=0,
i.e. as a regular enum type with no enumerators.  This patch changes
GCC to adopt that format, and makes a couple of minor cleanups in
btf_asm_type ().

gcc/

	PR debug/111735
	* btfout.cc (btf_fwd_to_enum_p): New.
	(btf_asm_type_ref): Special case references to enum forwards.
	(btf_asm_type): Special case enum forwards. Rename btf_size_type to
	btf_size, and change chained ifs switching on btf_kind into else ifs.

gcc/testsuite/

	PR debug/111735
	* gcc.dg/debug/btf/btf-forward-2.c: New test.

0 files changed, 0 insertions, 0 deletions