Re: [PATCH] Gold: Implement the '--discard-locals' and '-X' options.

[=?big5?b?RG91ZyBLd2FuICjD9q62vHcp?= <dougkwan at google dot com>]

Thanks for reviewing.  Here is an updated patch.

2009-06-05  Doug Kwan  <dougkwan@google.com>

        * Makefile.am (CCFILES): Add target.cc.
        * Makefile.in: Regenerate.
        * i386.cc (class Target_i386): Define new virtual method to
        override do_is_local_label_name in parent.
        * object.cc (Sized_relobj::do_count_local_symbols): Discard
        local symbols if --discard-locals or -X is given.
        * options.h (class General_options): Declare new options
        '--discard-locals' and '-X' for discarding locals.
        * target.h (class Target): Define new methods is_local_label_name.
        Declare new virtual method do_is_local_label_name.
        * target.cc: New file.
        * testsuite/Makefile.am (check_PROGRAMS): Add discard_locals_test.
        (check_SCRIPTS): Add discard_locals_test.sh.
        (check_DATA): Add discard_local_tests.syms.
        (discard_locals_test_SOURCES, discard_locals_test_LDFLAGS): Define.
        (discard_local_tests.syms, discard_locals_test.o): New make rules.
        * testsuite/Makefile.in: Regenerate.
        * testsuite/discard_locals_test.c: New file.
        * testsuite/discard_locals_test.sh: Same.


-Doug

2009/6/5 Ian Lance Taylor <iant@google.com>:
> "Doug Kwan (Ãö®¶¼w)" <dougkwan@google.com> writes:
>
>>        const char* name = pnames + sym.get_st_name();
>> +      if (discard_locals
>> +       && sym.get_st_type() != elfcpp::STT_FILE
>> +       && parameters->target().is_local_label_name(name))
>> +     {
>> +       lv.set_no_output_symtab_entry();
>> +          gold_assert(!lv.needs_output_dynsym_entry());
>> +       continue;
>> +     }
>
> Instead of asserting, don't discard the symbol if
> lv.needs_output_dynsym_entry() returns true.
>
>> +  // Virtual function which may be overriden by the child class.
>> +  virtual bool
>> +  do_is_local_label_name(const char* name) const
>> +  {
>> +    // The logic is the same as that in _bfd_elf_is_local_label_name().
>> +
>> +    // Normal local symbols start with ``.L''.
>> +    if (name[0] == '.' && name[1] == 'L')
>> +      return true;
>> +
>> +    // At least some SVR4 compilers (e.g., UnixWare 2.1 cc) generate
>> +    // DWARF debugging symbols starting with ``..''.
>> +    if (name[0] == '.' && name[1] == '.')
>> +      return true;
>> +
>> +    // gcc will sometimes generate symbols beginning with ``_.L_'' when
>> +    // emitting DWARF debugging output.  I suspect this is actually a
>> +    // small bug in gcc (it calls ASM_OUTPUT_LABEL when it should call
>> +    // ASM_GENERATE_INTERNAL_LABEL, and this causes the leading
>> +    // underscore to be emitted on some ELF targets).  For ease of use,
>> +    // we treat such symbols as local.
>> +    if (name[0] == '_' && name[1] == '.' && name[2] == 'L' && name[3] == '_')
>> +      return true;
>> +
>> +    return false;
>> +  }
>
> This is too big to define inline in the class.  Define it in target.h
> just below the class definition.  Add a target.cc file and define it
> there.
>
>> +# '-Wa,--keep-locals' is required to preserve the local label used for testing.
>> +discard_locals_test.o: discard_locals_test.c
>> +     $(COMPILE) -c -Wa,--keep-locals -o $@ $<
>
> s/--keep-locals/-L/g
>
>> +int
>> +main (void)
>> +{
>> +  /* local symbol format for generic ELF target. */
>> +  asm (".Lshould_be_discarded:");
>> +
>> +#ifdef __i386__
>> +  /* additional local symbol format for the i386 target. */
>> +  asm (".Xshould_be_discarded:");
>> +#endif
>> +
>> +  return 0;
>> +}
>
> I think it would be better to put the asm statements outside of the main
> function.
>
> Please send another patch with these changes for final approval.
>
> Thanks.
>
> Ian
>

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