Re: [PATCH 7/8] Remove the objfile backlink from comp_unit

["Christian Biesinger via gdb-patches" <gdb-patches@sourceware.org>]

On Sat, Feb 8, 2020, 10:28 Tom Tromey <tom@tromey.com> wrote:

> This removes the objfile backlink from comp_unit.  The only remaining
> uses involved fetching the text offset from the objfile.  However,
> this is already convenient computed at all the sites that call
>

convenient -> conveniently, I think?

execute_cfa_program, and so it can simply be passed in.
>
> gdb/ChangeLog
> 2020-02-08  Tom Tromey  <tom@tromey.com>
>
>         * dwarf2/frame.c (struct comp_unit) <objfile>: Remove.
>         (execute_cfa_program): Add text_offset parameter.
>         (execute_cfa_program_test, dwarf2_fetch_cfa_info)
>         (dwarf2_frame_cache): Update.
>         (dwarf2_build_frame_info): Don't set "objfile" member.
>
> Change-Id: I81b1c82d514dad83b3d00053756a07ef54b19796
> ---
>  gdb/ChangeLog      |  8 ++++++++
>  gdb/dwarf2/frame.c | 25 +++++++++++++------------
>  2 files changed, 21 insertions(+), 12 deletions(-)
>
> diff --git a/gdb/dwarf2/frame.c b/gdb/dwarf2/frame.c
> index d4f6165b75c..2c35016e2d9 100644
> --- a/gdb/dwarf2/frame.c
> +++ b/gdb/dwarf2/frame.c
> @@ -139,8 +139,6 @@ struct comp_unit
>    /* Keep the bfd convenient.  */
>    bfd *abfd = nullptr;
>
> -  struct objfile *objfile = nullptr;
> -
>    /* Pointer to the .debug_frame section loaded into memory.  */
>    const gdb_byte *dwarf_frame_buffer = nullptr;
>
> @@ -349,7 +347,8 @@ Not implemented: computing unwound register using
> explicit value operator"));
>  static const gdb_byte *
>  execute_cfa_program (struct dwarf2_fde *fde, const gdb_byte *insn_ptr,
>                      const gdb_byte *insn_end, struct gdbarch *gdbarch,
> -                    CORE_ADDR pc, struct dwarf2_frame_state *fs)
> +                    CORE_ADDR pc, struct dwarf2_frame_state *fs,
> +                    CORE_ADDR text_offset)
>  {
>    int eh_frame_p = fde->eh_frame_p;
>    unsigned int bytes_read;
> @@ -386,8 +385,8 @@ execute_cfa_program (struct dwarf2_fde *fde, const
> gdb_byte *insn_ptr,
>               fs->pc = read_encoded_value (fde->cie->unit,
> fde->cie->encoding,
>                                            fde->cie->ptr_size, insn_ptr,
>                                            &bytes_read,
> fde->initial_location);
> -             /* Apply the objfile offset for relocatable objects.  */
> -             fs->pc += fde->cie->unit->objfile->text_section_offset ();
> +             /* Apply the text offset for relocatable objects.  */
> +             fs->pc += text_offset;
>               insn_ptr += bytes_read;
>               break;
>
> @@ -646,7 +645,7 @@ execute_cfa_program_test (struct gdbarch *gdbarch)
>
>    const gdb_byte *insn_end = insns + sizeof (insns);
>    const gdb_byte *out = execute_cfa_program (&fde, insns, insn_end,
> gdbarch,
> -                                            0, &fs);
> +                                            0, &fs, 0);
>
>    SELF_CHECK (out == insn_end);
>    SELF_CHECK (fs.pc == 0);
> @@ -894,13 +893,14 @@ dwarf2_fetch_cfa_info (struct gdbarch *gdbarch,
> CORE_ADDR pc,
>
>    /* First decode all the insns in the CIE.  */
>    execute_cfa_program (fde, fde->cie->initial_instructions,
> -                      fde->cie->end, gdbarch, pc, &fs);
> +                      fde->cie->end, gdbarch, pc, &fs, text_offset);
>
>    /* Save the initialized register set.  */
>    fs.initial = fs.regs;
>
>    /* Then decode the insns in the FDE up to our target PC.  */
> -  execute_cfa_program (fde, fde->instructions, fde->end, gdbarch, pc,
> &fs);
> +  execute_cfa_program (fde, fde->instructions, fde->end, gdbarch, pc, &fs,
> +                      text_offset);
>
>    /* Calculate the CFA.  */
>    switch (fs.regs.cfa_how)
> @@ -1022,7 +1022,8 @@ dwarf2_frame_cache (struct frame_info *this_frame,
> void **this_cache)
>    /* First decode all the insns in the CIE.  */
>    execute_cfa_program (fde, fde->cie->initial_instructions,
>                        fde->cie->end, gdbarch,
> -                      get_frame_address_in_block (this_frame), &fs);
> +                      get_frame_address_in_block (this_frame), &fs,
> +                      cache->text_offset);
>
>    /* Save the initialized register set.  */
>    fs.initial = fs.regs;
> @@ -1037,7 +1038,7 @@ dwarf2_frame_cache (struct frame_info *this_frame,
> void **this_cache)
>      {
>        /* Decode the insns in the FDE up to the entry PC.  */
>        instr = execute_cfa_program (fde, fde->instructions, fde->end,
> gdbarch,
> -                                  entry_pc, &fs);
> +                                  entry_pc, &fs, cache->text_offset);
>
>        if (fs.regs.cfa_how == CFA_REG_OFFSET
>           && (dwarf_reg_to_regnum (gdbarch, fs.regs.cfa_reg)
> @@ -1052,7 +1053,8 @@ dwarf2_frame_cache (struct frame_info *this_frame,
> void **this_cache)
>
>    /* Then decode the insns in the FDE up to our target PC.  */
>    execute_cfa_program (fde, instr, fde->end, gdbarch,
> -                      get_frame_address_in_block (this_frame), &fs);
> +                      get_frame_address_in_block (this_frame), &fs,
> +                      cache->text_offset);
>
>    try
>      {
> @@ -2135,7 +2137,6 @@ dwarf2_build_frame_info (struct objfile *objfile)
>    /* Build a minimal decoding of the DWARF2 compilation unit.  */
>    unit = new comp_unit;
>    unit->abfd = objfile->obfd;
> -  unit->objfile = objfile;
>
>    if (objfile->separate_debug_objfile_backlink == NULL)
>      {
> --
> 2.17.2
>
>