Re: [patch for gcc12 stage1][version 2] add -ftrivial-auto-var-init and variable attribute "uninitialized" to gcc

[Qing Zhao <qing.zhao@oracle.com>]

> On Apr 27, 2021, at 1:30 AM, Richard Biener <rguenther@suse.de> wrote:
> 
>> 
>> equivalent in all respects.  And if we were trying to make them
>> equivalent, we'd need to do much more than this.
>> 
>> The same applies to the pattern case.  If “x” is initialised to a pattern
>> that happens to point to a real decl, we don't have to preserve the
>> order of accesses to the decl wrt accesses to “*x” (especially since
>> we're hoping that “*x” will trap).
>> 
>> I think for aliasing purposes, the .DEFERRED_INIT return value is still
>> analogous to an undefined SSA name, even though we will later generate
>> code to initialise it.
> 
> (only replying to this part, I'll look at the next revised patch series)

Okay, thanks.

> 
> Since .DEFERRED_INIT does not produce any pointers and is not a real
> initialization you don't need to do anything in PTA - but you might
> want to ignore it to not pessimize it by the default handling.  Thus
> 
> +  if (gimple_call_internal_p (t, IFN_DEFERRED_INIT))
> +    {
> +      find_func_aliases_for_deferred_init (t);
> +      return;
> +    }
> 
> should simply return and find_func_aliases_for_deferred_init can be 
> removed.

Okay. Will do that.

thanks.

Qing