Re: [PATCH] handle bzero/bcopy in DSE and aliasing (PR 80933, 80934)

[Richard Biener <richard dot guenther at gmail dot com>]

On Fri, Jun 9, 2017 at 3:04 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> On Fri, Jun 09, 2017 at 02:35:45PM +0200, Richard Biener wrote:
>> +static bool
>> +gimple_fold_builtin_bcmp (gimple_stmt_iterator *gsi)
>> +{
>>
>> +  /* Transform bcmp (a, b, len) into memcmp (a, b, len).  */
>> +
>> +  gimple *stmt = gsi_stmt (*gsi);
>> +  tree a = gimple_call_arg (stmt, 0);
>> +  tree b = gimple_call_arg (stmt, 1);
>> +  tree len = gimple_call_arg (stmt, 2);
>> +
>> +  gimple_seq seq = NULL;
>> +  gimple *repl = gimple_build_call (fn, 3, a, b, len);
>> +  gimple_seq_add_stmt_without_update (&seq, repl);
>> +  gsi_replace_with_seq_vops (gsi, seq);
>>
>> given they have the same prototype you can do like gimple_fold_builtin_stpcpy:
>>
>>   gimple_call_set_fndecl (stmt, fn);
>>   fold_stmt (gsi);
>>
>> That works even with bcopy -> memmove if you swap arguments.
>
> Shouldn't it also update gimple_call_fntype though, at least for memmove?
> Those differ with void const * vs. void * arguments, and also in the return
> value.  At least if the old fntype is compatible with the bcopy call.

Yes.  If the old fntype isn't compatible we don't reach the folding.

Richard.

>         Jakub