Segher,

     Gentle ping this:

	https://gcc.gnu.org/pipermail/gcc-patches/2020-September/553486.html
Thanks
Gui Haochen

On 9/9/2020 下午 4:55, HAO CHEN GUI wrote:
> Hi Segher,
>
>     Thanks for your advice. I removed macros defined in linux64.h and 
> linux.h. So they take relative jump tables by default. When 
> no-relative-jumptables is set, the absolute jump tables are taken. All 
> things relevant to section relocations are put in another patch. 
> Thanks again.
>
>
> On 8/9/2020 上午 5:46, Segher Boessenkool wrote:
>> On Mon, Aug 24, 2020 at 03:48:43PM +0800, HAO CHEN GUI wrote:
>>>> I'll try to be quicker at reviewing iterations of this -- there is 
>>>> quite
>>>> some way to go, without me slowing things down!
>> Sigh :-(
>>
>>>     * config/rs6000/linux.h (rs6000_relative_jumptables): Define.
>> That macro looks like it is variable (or function).  *Make* it a
>> variable, please?
>>
>>>     * config/rs6000/rs6000.c (TARGET_ASM_GENERATE_PIC_ADDR_DIFF_VEC):
>>>     Define
>> Period?
>>
>>>     (rs6000_gen_pic_addr_diff_vec, rs6000_output_addr_vec_elt): 
>>> Implement.
>> "New function."
>>
>>>     * config/rs6000/rs6000.md (absolute_tablejumpsi,
>>>     absolute_tablejumpsi_nospec, absolute_tablejumpdi,
>>>     absolute_tablejumpdi_nospec): Add four new expansions.
>> "New define_expands." or "New expanders."
>>
>>>     * config/rs6000/rs6000.opt (mrelative-jumptables): Add a new 
>>> option and
>>>     set rs6000_relative_jumptables to true by default.
>> "rs6000.opt: Add -mrelative-jumptables."
>>
>>> +/* Disable relative jump tables for Power Linux.  */
>>> +#undef rs6000_relative_jumptables
>>> +#define rs6000_relative_jumptables 0
>> Why?
>>
>>> +/* Disable relative jump tables for Power Linux64.  */
>>> +#undef rs6000_relative_jumptables
>>> +#define rs6000_relative_jumptables 0
>> (That's not what it's called...  Just don't say the "for..." at all?
>> It is clear from what file it is in.)
>>
>>>   /* Indicate that jump tables go in the text section.  */
>>>   #undef  JUMP_TABLES_IN_TEXT_SECTION
>>> -#define JUMP_TABLES_IN_TEXT_SECTION TARGET_64BIT
>>> +#define JUMP_TABLES_IN_TEXT_SECTION rs6000_relative_jumptables
>> Not sure that is correct.  Maybe the patch using rodata (.data.rel.ro)
>> should be a separate patch?
>>
>>>   /* Define as C expression which evaluates to nonzero if the tablejump
>>>      instruction expects the table to contain offsets from the 
>>> address of the
>>>      table.
>>>      Do not define this if the table should contain absolute 
>>> addresses.  */
>>> -#define CASE_VECTOR_PC_RELATIVE 1
>>> +#define CASE_VECTOR_PC_RELATIVE 0
>> This should depend on the new flag?
>>
>>> +/* Specify the machine mode that this machine uses
>>> +   for the index in the tablejump instruction.  */
>>> +#define CASE_VECTOR_MODE \
>>> +  (TARGET_32BIT || rs6000_relative_jumptables ? SImode : DImode)
>> rs6000_relative_jumptables ? SImode : Pmode;
>>
>>> +      if (rs6000_relative_jumptables)
>>> +    {
>>> +      if (TARGET_32BIT)
>>> +        emit_jump_insn (gen_tablejumpsi (operands[0], operands[1]));
>>> +      else
>>> +        emit_jump_insn (gen_tablejumpdi (operands[0], operands[1]));
>>> +    }
>> Hrm, I guess we should make that a parameterized name (future work,
>> don't do it now :-) )
>>
>>> +(define_expand "absolute_tablejumpsi"
>> Don't prefix names; it should start with "tablejump".
>>
>>
>> Segher