[PATCH] Fold __builtin_memchr (version 3)

Richard Biener richard.guenther@gmail.com
Wed Oct 12 08:34:00 GMT 2016


On Tue, Oct 11, 2016 at 11:38 AM, Martin Liška <mliska@suse.cz> wrote:
> On 10/07/2016 01:01 PM, Richard Biener wrote:
>> On Fri, Oct 7, 2016 at 10:41 AM, Martin Liška <mliska@suse.cz> wrote:
>>> Resending the patch, where I implemented folding in gimple-fold.c
>>>
>>> Patch can bootstrap on ppc64le-redhat-linux and survives regression tests.
>>
>> +/* Fold a call to the str{n}{case}cmp builtin pointed by GSI iterator.
>> +   FCODE is the name of the builtin.  */
>>
>> wrong comment
>
> Fixed.
>
>>
>> +static bool
>> +gimple_fold_builtin_memchr (gimple_stmt_iterator *gsi)
>>
>> +       {
>> +         replace_call_with_value (gsi, build_int_cst (type, 0));
>>
>> use ptr_type_node (void *) instead of type here and below.
>
> Done.
>
>>
>> +         HOST_WIDE_INT offset = r - p1;
>> +         if (compare_tree_int (len, offset) <= 0)
>> +           {
>>
>> == 0 can occur in which case we have to return a pointer to the
>> first char.  I think len < offset can't happen with memchr?
>
> Here I reworked the patch as it's not desired to trigger an undefined behavior
> in a host compiler for cases like: memchr ("", 'x', 5). Thus I switched to strchr
> and aforementioned hunk would make sense.
>
>>
>> +             replace_call_with_value (gsi, build_int_cst (type, 0));
>> +             return true;
>> +           }
>> +         else
>> +           {
>> +             tree temp = fold_build_pointer_plus_hwi_loc (loc, arg1, offset);
>> +             replace_call_with_value (gsi, temp);
>>
>> That yields valid GIMPLE by chance, I'd prefer if you'd built that to a
>> stmt and use the replace-with-vops.
>
> Done.
>
> Apart from that I added handling of lhs and the patch supports folding
> of CFN_BUILT_IN_MEMCHR.
>
> One question that comes to my mind is whether there's a possibility
> to fully test gimple folding of all cases if some of them are already
> eaten by generic folding?
>
> Tests of the series have been running.

Ok.

Thanks,
Richard.

> Martin
>
>>
>> +             return true;
>> +           }
>>
>>
>>> Ready to be installed?
>>> Martin
>



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