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Re: [PATCH] pointer arguments should not be value escaping initial when -fargument-noalias-global used
- From: Daniel Berlin <dberlin at dberlin dot org>
- To: Andrew Pinski <pinskia at physics dot uc dot edu>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Thu, 26 Jan 2006 23:56:43 -0500
- Subject: Re: [PATCH] pointer arguments should not be value escaping initial when -fargument-noalias-global used
- References: <245166a5b89a0bafebf98edc74faff3b@physics.uc.edu>
On Thu, 2006-01-26 at 22:19 -0500, Andrew Pinski wrote:
> We currently mark pointer arguments as initial value escaping but with
> flag_argument_noalias being greater than 1, we should not mark them
> as the value could not have escaped anywhere. This is because the
> value could not be pointer to globals or any other argument with that
> option supplied.
This is not the definition of value escaping.
Value escaping means it is passed by address somewhere else, and thus,
whatever it can point to, can now be pointed to by something outside of
our function.
(Whether this changes whether your patch is correct or not, is not
clear)
>
> This is still does not cause the arguments to become not call clobbered
> but that is a different issue, relating to name tags and type tags being
> call clobbered by default.
Errr, neither are clobbered by default, so i'm not sure what you are
talking about.
>
> OK? Bootstrapped and tested on x86_64-linux-gnu.
>
> Thanks,
> Andrew Pinski
>
> ChangeLog:
>
> * tree-ssa-alias.c (set_initial_properties);
> When flag_argument_noalias is greater than 1, don't mark
> PARM_DECLs as initial value escaping.
>
>