Re: RFC: explicitely mark out-of-scope deaths

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

On Thu, May 26, 2011 at 4:00 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> On Thu, May 26, 2011 at 03:43:45PM +0200, Michael Matz wrote:
>> --- tree-stdarg.c.orig ? ? ? ?2011-05-26 14:15:01.000000000 +0200
>> +++ tree-stdarg.c ? ? 2011-05-26 14:15:41.000000000 +0200
>> @@ -872,8 +872,12 @@ execute_optimize_stdarg (void)
>> ? ? ? ? ? ? ? ? if (get_gimple_rhs_class (gimple_assign_rhs_code (stmt))
>> ? ? ? ? ? ? ? ? ? ? == GIMPLE_SINGLE_RHS)
>> ? ? ? ? ? ? ? ? ? {
>> + ? ? ? ? ? ? ? ? ? /* Check for ap ={v} {}. ?*/
>> + ? ? ? ? ? ? ? ? ? if (TREE_CODE (rhs) == CONSTRUCTOR
>> + ? ? ? ? ? ? ? ? ? ? ? ? ? ?&& TREE_THIS_VOLATILE (rhs))
>> + ? ? ? ? ? ? ? ? ? ? continue;
>> ? ? ? ? ? ? ? ? ? ? /* Check for ap[0].field = temp. ?*/
>> - ? ? ? ? ? ? ? ? ? if (va_list_counter_struct_op (&si, lhs, rhs, true))
>> + ? ? ? ? ? ? ? ? ? else if (va_list_counter_struct_op (&si, lhs, rhs, true))
>> ? ? ? ? ? ? ? ? ? ? ? continue;
>
> Perhaps optimize_stdarg_builtin could fold __builtin_va_end into
> this ap ={v} {} for non-pointer va_list to make it clear the variable
> is undefined afterwards, currently it just optimizes it away completely.

Btw, I suggested to use { <error_mark> } for the "undefinedness".

Repeated code asks for something like gimple_clobber_p () and
gimple_clobber_rhs_p ().

Richard.