Hi, Richi,
Sorry if this comes in late. I'd saved your message for careful
analysis and I only got back to it now.
On Aug 1, 2012, Richard Guenther <richard.guent...@gmail.com> wrote:
> On Fri, Dec 2, 2011 at 8:28 PM, Jakub Jelinek <ja...@redhat.com> wrote:
>> PR debug/50317
>> * tree-ssa.c (target_for_debug_bind): Also allow is_gimple_reg_type
>> vars that aren't referenced.
>> (tree-ssa-live.c (remove_unused_locals): Don't clear TREE_ADDRESSABLE
>> of unreferenced local vars.
>> * cfgexpand.c (expand_debug_expr): For DEBUG_IMPLICIT_PTR allow also
>> TREE_ADDRESSABLE vars that satisfy target_for_debug_bind.
> But we do _not_ want to
> have used non-register (but register type) variables tracked because we
> do not track aliases?
The reasoning, back when I wrote target_for_debug_bind, was that it
didn't make sense to enable VTA for variables that were addressable,
because the location of addressable variables isn't subject to change.
Since their location is a constant address, we're better off avoiding
all the VTA location wrangling and just using their unchanging MEM
location.
> - if (!is_gimple_reg (var))
> - {
> - if (is_gimple_reg_type (TREE_TYPE (var))
> - && referenced_var_lookup (cfun, DECL_UID (var)) == NULL_TREE)
> - return var;
> - return NULL_TREE;
> - }
> + /* var-tracking only tracks registers. */
> + if (!is_gimple_reg_type (TREE_TYPE (var)))
> + return NULL_TREE;
This change, although not incorrect, would subject lots of variables
unnecessary VTA treatment, growing memory use and compile time.
--
Alexandre Oliva, freedom fighter http://FSFLA.org/~lxoliva/
You must be the change you wish to see in the world. -- Gandhi
Be Free! -- http://FSFLA.org/ FSF Latin America board member
Free Software Evangelist Red Hat Brazil Compiler Engineer
