Re: [PATCH 01/11] gen: Emit error msg for empty split condition

["Kewen.Lin" <linkw@linux.ibm.com>]

Hi Richi,

on 2021/6/2 下午3:04, Richard Biener wrote:
> On Wed, Jun 2, 2021 at 7:05 AM Kewen Lin <linkw@linux.ibm.com> wrote:
>>
>> As Segher suggested, this patch is to emit the error message
>> if the split condition of define_insn_and_split is empty while
>> the insn condition isn't.
> 
> I wonder whether it would be a good idea to automagically make
> the split condition "&& 1" via gensupport?
> 

Thanks for the comment!  Do you happen to have some similar examples?
IIUC this idea has to lay on the assumption always holding that when
one developer puts split condition as blank meanwhile leaves insn
condition as non-empty, he/she exactly wants to make split condition
the same as insn condition.  Once one developer doesn't think like
that way (that is to want split to deal with more), the automatic
condtion filling seems to over fill.

The way that the current patch provided is not to allow the developer
to write that kind of pattern, instead he/she has to go with separated
define_insn and define_split.

BR,
Kewen

>> gcc/ChangeLog:
>>
>>         * gensupport.c (process_rtx): Emit error message for empty
>>         split condition in define_insn_and_split while the insn
>>         condition isn't.
>> ---
>>  gcc/gensupport.c | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/gcc/gensupport.c b/gcc/gensupport.c
>> index 0f19bd70664..52cee120215 100644
>> --- a/gcc/gensupport.c
>> +++ b/gcc/gensupport.c
>> @@ -620,6 +620,9 @@ process_rtx (rtx desc, file_location loc)
>>           }
>>         else if (GET_CODE (desc) == DEFINE_INSN_AND_REWRITE)
>>           error_at (loc, "the rewrite condition must start with `&&'");
>> +       else if (split_cond[0] == '\0' && strlen (XSTR (desc, 2)) != 0)
>> +         error_at (loc, "the split condition mustn't be empty if the "
>> +                        "insn condition isn't empty");
>>         XSTR (split, 1) = split_cond;
>>         if (GET_CODE (desc) == DEFINE_INSN_AND_REWRITE)
>>           XVEC (split, 2) = gen_rewrite_sequence (XVEC (desc, 1));
>> --
>> 2.17.1
>>