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[DebugInfo] Support typedef with btf_decl_tag attributes

Authored by yonghong-song on Sep 20 2021, 5:08 PM.

Description

[DebugInfo] Support typedef with btf_decl_tag attributes

Clang patch ([1]) added support for btf_decl_tag attributes with typedef
types. This patch added llvm support including dwarf generation.
For example, for typedef

typedef unsigned * __u __attribute__((btf_decl_tag("tag1")));
__u u;

the following shows llvm-dwarfdump result:

 0x00000033:   DW_TAG_typedef
                 DW_AT_type      (0x00000048 "unsigned int *")
                 DW_AT_name      ("__u")
                 DW_AT_decl_file ("/home/yhs/work/tests/llvm/btf_tag/t.c")
                 DW_AT_decl_line (1)

 0x0000003e:     DW_TAG_LLVM_annotation
                   DW_AT_name    ("btf_decl_tag")
                   DW_AT_const_value     ("tag1")

 0x00000047:     NULL

[1] https://reviews.llvm.org/D110127

Differential Revision: https://reviews.llvm.org/D110129

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