Re: [PATCH] btf: Add support to BTF_KIND_ENUM64 type

[Guillermo E. Martinez via Gcc-patches]

On 9/28/22 13:45, David Faust wrote:
Hi Guillermo,


Hi David,

Thanks for the patch. Just a couple of small nits on the changelog
entries below but otherwise very nice, LGTM.

But, please wait a couple of days before pushing to give Indu time
to raise any objections about the changes in ctfc/dwarf2ctf.


OK. Thanks for your comments!.
 
Thanks!
David

On 8/29/22 14:11, Guillermo E. Martinez via Gcc-patches wrote:
Hello GCC team,

The following patch update BTF/CTF backend to support
BTF_KIND_ENUM64 type.

Comments will be welcomed and appreciated!,

Kind regards,
guillermo
--

BTF supports 64-bits enumerators with following encoding:

   struct btf_type:
     name_off: 0 or offset to a valid C identifier
     info.kind_flag: 0 for unsigned, 1 for signed
     info.kind: BTF_KIND_ENUM64
     info.vlen: number of enum values
     size: 1/2/4/8

The btf_type is followed by info.vlen number of:

     struct btf_enum64
     {
       uint32_t name_off;   /* Offset in string section of enumerator name.  */
       uint32_t val_lo32;   /* lower 32-bit value for a 64-bit value Enumerator 
*/
       uint32_t val_hi32;   /* high 32-bit value for a 64-bit value Enumerator 
*/
     };

So, a new btf_enum64 structure was added to represent BTF_KIND_ENUM64
and a new field in ctf_dtdef to represent specific type's properties, in
the particular case for CTF enums it helps to distinguish when its
enumerators values are signed or unsigned, later that information is
used to encode the BTF enum type.

gcc/ChangeLog:

        * btfout.cc (btf_calc_num_vbytes): Compute enumeration size depending of
        enumerator type btf_enum{,64}.
        (btf_asm_type): Update btf_kflag according to enumerators sign,
        using correct BPF type in BTF_KIND_ENUMi{,64}.
        (btf_asm_enum_const): New argument to represent the size of
        the BTF enum type.
        * ctfc.cc (ctf_add_enum): Use and initialization of flag field to
        CTF_ENUM_F_NONE.
        (ctf_add_enumerator): New argument to represent CTF flags,
        updating the comment and flag vaue according to enumerators
        sing.
        * ctfc.h (ctf_dmdef): Update dmd_value to HOST_WIDE_INT to allow
        use 32/64 bits enumerators.
        (ctf_dtdef): Add flags to to describe specifyc type's properties.

typo: specific


Fixed in v2.

        * dwarf2ctf.cc (gen_ctf_enumeration_type): Update flags field
        depending when a signed enumerator value is found.
        include/btf.h (btf_enum64): Add new definition and new symbolic
        constant to BTF_KIND_ENUM64 and BTF_KF_ENUM_{UN,}SIGNED.

Missing an * here for include/btf.h


Fixed in v2.


gcc/testsuite/ChangeLog:

        gcc.dg/debug/btf/btf-enum-1.c: Update testcase, with correct
        info.kflags encoding.
        gcc.dg/debug/btf/btf-enum64-1.c: New testcase.

Likewise for these ChangeLog entries.


Fixed in v2.

You can use contrib/gcc-changelog/git_check_commit.py to check the
formatting of the entries.


Oh. thanks for mention it, really useful.

---
  gcc/btfout.cc                                 | 24 ++++++++---
  gcc/ctfc.cc                                   | 14 ++++---
  gcc/ctfc.h                                    |  9 +++-
  gcc/dwarf2ctf.cc                              |  9 +++-
  gcc/testsuite/gcc.dg/debug/btf/btf-enum-1.c   |  2 +-
  gcc/testsuite/gcc.dg/debug/btf/btf-enum64-1.c | 41 +++++++++++++++++++
  include/btf.h                                 | 19 +++++++--
  7 files changed, 99 insertions(+), 19 deletions(-)
  create mode 100644 gcc/testsuite/gcc.dg/debug/btf/btf-enum64-1.c

diff --git a/gcc/btfout.cc b/gcc/btfout.cc
index 997a33fa089..4b11c867c23 100644
--- a/gcc/btfout.cc
[...]

Regards,
guillermo